TW202422125A - Transfer-printed micro-optical components - Google Patents

Abstract

An exemplary micro-optical component includes a micro-substrate and a micro-optical element disposed on the micro-substrate. The micro-optical element is structured to modify or process light. At least a portion of a component tether is physically attached to the micro-substrate or physically attached to the micro-optical element. The micro-optical component has a thickness less than 250 µm. Light can be processed by reflection, refraction, diffraction, frequency changes, polarization changes, color-temperature or frequency distribution changes, or phase changes. The micro-optical component can be disposed on a system substrate to form a micro-optical system. The system substrate can include a cavity and the micro-optical element can be disposed at least partially in the cavity. Micro-optical components can be passive optical micro-devices. A light-active element can be disposed on the micro-substrate to receive light from or emit light to the micro-optical element.

Description

Transferred micro-optical components

The present disclosure generally relates to transferable micro-optical components.

Photonic systems use light sensing components, light emitting components, and light conditioning components to manipulate light (e.g., photons) typically for applications in telecommunications. Such systems often rely on integrated circuits using compound semiconductors to efficiently generate and amplify light, for example using lasers and optical amplifiers. The generated light can be modulated, for example, with salts such as lithium niobate and detected, for example, with photodiodes having semiconductor p-n junctions that generate current in response to exposure. Light can also be guided, for example, using waveguides or light pipes constructed using materials such as silicon nitride or optical elements that are substantially transparent at the desired wavelength of light corresponding to the light being emitted, conditioned, or detected.

Modern silicon wafers are processed at extremely high resolution, e.g., having features 10 nm or less in size or having features 10 nm or less apart, or both, to produce dense and fast integrated circuits. Such small feature sizes are a result of expensive photolithography tools, the cost of which is justified by the extremely large volumes of silicon integrated circuits (e.g., CMOS circuits) that can be processed with such tools. The extremely large volumes of silicon integrated circuits, in turn, have led to the development of low-cost and relatively large source silicon wafers (e.g., 300 mm in diameter). The combination of low-cost and bulk silicon source materials and sophisticated processing equipment (particularly, high-resolution masking and exposure equipment) has enabled the low-cost and ubiquitous silicon integrated circuits found in most electronic devices today.

However, silicon is not the most suitable material for all desired semiconductor devices and functions. For example, compound semiconductor materials such as InP, GaAs and GaN and many other III/V material combinations can provide, for example, greater electron mobility, superior light emission or superior sensor sensitivity, and are therefore more suitable for certain applications, especially high-power electrical devices and photonic devices (e.g., lasers and LEDs). Because these applications are often relatively recently developed and manufactured at relatively low volumes than silicon devices, the availability and cost of photolithography processing equipment and the wafer size of compound semiconductor materials are disadvantageous relative to silicon. Basically, compound semiconductor materials and processing are more expensive and are manufactured at lower resolution than silicon (thus making compound semiconductor components larger and more expensive to manufacture). In some systems, photonic components are controlled by silicon circuits such as CMOS circuits.

Optical components such as reflectors, refractors, or diffractors may also be used in photonic systems. Conventional optical components may be too large for miniaturized optical and photonic systems. Therefore, structures, systems, and methods for small, high-resolution compound semiconductor devices, silicon devices, and optical components for photonic and optical systems are needed.

The present disclosure provides, inter alia, devices, structures, systems and construction methods for micro-optical elements, micro-optical assemblies and micro-optical systems. Such devices, structures or systems may include light emitters, light detectors, light processors, light modulators and light transmitters (e.g., lasers, photodiodes, phototransistors, optical modulators, optical amplifiers and optical waveguides). Such micro-optical structures are useful for photonic systems, such as photonic integrated circuits that combine electrical integrated circuits (e.g., silicon circuits such as CMOS) with optical emitters (such as light emitting diodes or LEDs and lasers), optical sensors (such as photodiodes), and optical structures (such as mirrors, partially reflecting mirrors, prisms, lenses, filters, diffusers, beam shaping optical elements and gratings) that provide one or more of reflection, refraction, polarization detection or modulation, filtering, or diffraction of light (e.g., photons), thereby processing or modulating the photons. Embodiments of the present disclosure may also include waveguides or light pipes for transporting photons from one location to another.

According to embodiments of the present disclosure, a micro-optical assembly includes a micro-substrate having a micro-substrate region and a micro-optical element disposed on the micro-substrate. The micro-optical element may be a passive optical component that modulates photons or one or more photonic properties but is not electrically active. At least a portion of an assembly tether may be physically attached to the micro-substrate or physically attached to the micro-optical element. The assembly tether may be intact, such as for a micro-optical assembly on an assembly source wafer, or may be damaged (e.g., cracked) or separated, such as for a micro-optical assembly microprinted to a system substrate.

The micro-optical component may have a thickness (e.g., a height or a depth or both) of no more than 250 μm (e.g., less than 250 μm, no more than 200 μm, no more than 150 μm, no more than 100 μm, no more than 75 μm, no more than 50 μm, no more than 25 μm, or no more than 10 μm). A thickness, height, or depth of a micro-optical element may be the combined height, depth, or thickness of a micro-substrate and a micro-optical element together in a direction orthogonal to a surface of a micro-substrate on which the micro-optical element is disposed. The micro-optical element may have a micro-optical element area above the micro-substrate, and the micro-substrate area may be larger than the micro-optical element area, the micro-substrate area may be equal to the micro-optical element area, or the micro-substrate area may be smaller than the micro-optical element area. In some embodiments, the micro-substrate extends beyond a micro-optical element in only one dimension (e.g., in a direction parallel to the surface of the micro-substrate). In some embodiments, the micro-substrate extends beyond the micro-optical element in two dimensions (eg, in orthogonal directions parallel to the surface of the micro-substrate).

According to embodiments of the present disclosure, the micro-optical element may be a reflective element, a refractive element, a diffraction element, a frequency filter, a phase change element, a polarization detector, a polarization modulator (e.g., a polarization rotator or a polarization filter), a filter, a frequency converter, or any combination thereof. In some embodiments, the micro-optical element is a lens or a prism. The micro-optical element may be disposed on the surface of the micro-substrate or formed in the micro-substrate. The micro-optical element may extend away from the micro-substrate in a direction perpendicular to the surface of the micro-substrate.

In some embodiments, a micro-optical assembly includes a photoactive element, such as an electro-active light generating, light modulating or light responsive element (e.g., a photoactive element that generates light, responds to light or modulates light in conjunction with a received or generated electrical signal, such as a photoactive assembly) disposed on the micro-substrate on a side of the micro-substrate opposite the micro-optical element. For example, the micro-optical element may be disposed on a first surface or first side of the micro-substrate, and the photoactive element may be disposed on a second surface or second side of the micro-substrate opposite and substantially parallel to the first surface or first side of the micro-substrate. The photoactive element may transmit light to the micro-optical element or receive light from the micro-optical element. The light generating element may be a laser or a light emitting diode, the light responsive element may be a photodiode or a phototransistor, and the light modulating element may be an optical amplifier or an optical modulator. In some embodiments, the micro substrate includes a micro alignment mark disposed in a region of the micro substrate excluding the region of the micro optical element. The micro substrate may be substantially transparent to light modulated by the micro optical element, the micro substrate may be substantially reflective to light modulated by the micro optical element, or the micro substrate may be substantially opaque to or absorb light modulated by the micro optical element or stray light or ambient light.

In some embodiments of the present disclosure, the micro-substrate and the micro-optical element are integral. For example, the micro-optical component can be monolithic and can include common materials formed in a common construction or manufacturing step (e.g., by embossing, two-photon polymerization, or photolithography).

In some embodiments, the microsubstrate and the micro-optical element comprise different materials, the microsubstrate and the micro-optical element comprise different structures adhered together, or both, and are therefore not unitary or monolithic. In some embodiments of the present disclosure, the microsubstrate has a microsubstrate area defined by the microsubstrate length multiplied by the microsubstrate width, the microsubstrate area being no greater than 100,000 µm ² (e.g., no greater than 62,500 µm ² , less than 62,500 µm 2, no greater than 40,000 µm ² , less than 40,000 µm ² , no greater than 20,000 µm ² , no greater than 10,000 µm ² , no greater than 2,500 µm ² , no greater than 400 µm ^{2 ,} or no greater than 100 µm ² ). In some embodiments, the micro substrate has an aspect ratio (length to width) of, for example, not less than 2: 1, not less than 4: 1, not less than 5: 1, not less than 8: 1, or not less than 10: 1. In some embodiments, the micro substrate has a width of not more than 50 μm and a length of not less than 100 μm, 200 μm, 250 μm, or 500 μm, or has a width of not more than 100 μm and a length of not less than 500 μm, 750 μm, or 1000 μm. In some embodiments, the microsubstrate has a width of no greater than 200 µm and a length of no less than 400 µm, 600 µm, 800 µm, 1000 µm, 1200 µm, 1400 µm, 1600 µm, 1800 µm, or 2000 µm.

According to an embodiment of the present disclosure, a micro-optical component includes a protective layer or multiple protective layers. The protective layer or layers can be constructed to interact with light as desired.

In some embodiments, the assembly tape comprises a portion of the protective layer. In some embodiments, the assembly tape is a hybrid organic-inorganic tape.

According to an embodiment of the present disclosure, a micro-optical system includes a system substrate and a micro-optical component disposed on the system substrate. The micro-optical component may be non-native to the system substrate. In some embodiments, the micro-optical component extends in a direction away from the system substrate. In some embodiments, the micro-optical system includes a waveguide or light pipe disposed on or in the system substrate and optically connected to the micro-optical component. In some embodiments, the system substrate includes a cavity, and the micro-optical component is at least partially disposed in the cavity.

In some embodiments, the micro-substrate is disposed in the cavity. In some embodiments, one or both of the micro-optical element and the micro-substrate are adhered to a surface (e.g., a side or a bottom plate) of the cavity, for example, with an adhesive (such as an optically clear adhesive or an optical index matching adhesive). Some embodiments include a light pipe disposed in or on the system substrate, the light pipe being disposed to transmit light entering or leaving the micro-optical element. In some embodiments, a micro-optical assembly includes an optically active element disposed on the micro-substrate on a side of the micro-substrate and the micro-optical element, the system substrate is a semiconductor substrate, and the semiconductor substrate includes an electronic circuit electrically connected to the optically active element. The electronic circuit can electrically control the optically active element or respond to the optically active element.

In some embodiments of the present disclosure, the system substrate includes a micro-alignment mark disposed on or in a surface of the system substrate. The micro-alignment mark can be disposed on or in the surface of the system substrate in a manner that is aligned with an alignment mark disposed in or on the micro-optical component (e.g., disposed on the micro-substrate outside the micro-optical element area).

In some embodiments of the present disclosure, the micro-optical system is a photonic integrated circuit.

In some embodiments, the system substrate includes a cavity and the micro-optical element is at least partially disposed in the cavity. In some embodiments, the micro-optical system includes an adhesive that adheres the micro-optical element to the micro-substrate or adheres the micro-optical assembly to the system substrate or to a wall or floor (bottom) of a cavity in the system substrate. In some embodiments, the micro-optical system includes an optical index matching material (e.g., an optically clear adhesive) disposed on any of the micro-optical element, the micro-substrate, or the system substrate. An optical index matching material or adhesive may fill a gap between the micro-optical element and the micro-substrate or between the micro-optical assembly (e.g., the micro-optical element) and the system substrate (e.g., in a cavity in the system substrate).

Thus, according to embodiments of the present disclosure, a cavity in a system substrate has one or more cavity sides (e.g., walls) extending into the system substrate, and the micro-optical element is disposed in contact with one or more of the cavity sides. In some embodiments, the micro-optical element is disposed in the cavity but does not contact any of the cavity sides or the floor. In some embodiments, the micro-optical element extends out of the cavity, such as above a surface of the system substrate. In some embodiments, the micro-substrate is at least partially disposed in the cavity. In some embodiments, the micro-substrate is disposed exclusively in the cavity. A surface of the micro-substrate may be substantially in a common plane with a surface of the system substrate (e.g., within manufacturing tolerances). In some embodiments, the cavity has one or more cavity sides or walls extending into the system substrate, and the micro substrate is disposed in contact with one or more of the cavity sides or walls. In some embodiments, the cavity has a cavity floor (e.g., cavity bottom) in the system substrate, and the micro substrate is disposed in contact with the cavity floor, for example, adhered to the cavity floor with an adhesive (e.g., an optical index matching adhesive).

In some embodiments of micro-optical systems according to the present disclosure, the system substrate includes a structural (e.g., mechanical) stop disposed on a surface of the system substrate, and the micro-optical component contacts or adheres to the structural stop. The structural stop can be formed, for example, photolithographically in or on the system substrate surface, or can be a side (e.g., a wall) of a cavity formed in the system substrate, for example, by etching or embossing the system substrate according to a pattern. The micro-substrate or the micro-optical element (or both) can be adjacent to, contact, or adhere to the structural stop.

According to an embodiment of the present disclosure, a micro-optical component source wafer includes: a source wafer including one or more sacrificial portions separated by one or more anchor portions; and a micro-optical component disposed entirely and directly above each of the one or more sacrificial portions and physically attached to one of the one or more anchor portions by a strap.

According to an embodiment of the present disclosure, a method of manufacturing a micro-optical system includes providing a micro-optical component source wafer, providing a stamp, providing a system substrate, contacting the stamp to the micro-optical component, removing the micro-optical component from the micro-optical component source wafer with the stamp, contacting the micro-optical component to the system substrate with the stamp, and removing the stamp from the micro-optical component and the system substrate. In some embodiments, an adhesive layer is disposed on the system substrate, and the micro-optical component contacts and adheres to the adhesive layer and the system substrate.

According to an embodiment of the present disclosure, a method for manufacturing a micro-optical system includes providing a micro-optical component source wafer, providing a first stamp and a second stamp, providing a system substrate, making the first stamp contact a first side of the micro-optical component, removing the micro-optical component from the micro-optical component source wafer with the first stamp, making the micro-optical component contact a second side of the micro-optical component opposite to the first side with the second stamp, making the first side of the micro-optical component contact the system substrate with the second stamp, and removing the second stamp from the micro-optical component and the system substrate.

A method of manufacturing a system (e.g., a micro-optical system) according to the present disclosure may include: providing a micro-optical component source wafer, the micro-optical component source wafer having one or more sacrificial portions separated by one or more anchor portions; coating at least a portion of the one or more sacrificial portions with a liquid curable polymer; forming a structure (e.g., a micro-optical component), wherein forming the structure includes using two-photon polymerization to cure only a portion of the liquid curable polymer to form at least a portion of the structure, such as a micro-optical component; forming an assembly ties between the micro-optical component and one of the one or more anchor portions; and removing an uncured portion of the liquid curable polymer to form a gap between the structure and the component source wafer and form a micro-transferable structure. In some embodiments, the sacrificial portion is a cavity, and embodiments include disposing at least a portion of the liquid curable polymer in the cavity and curing only a portion of the liquid curable polymer in the cavity to form at least a portion of the structure (e.g., a micro-optical component) in the cavity. In some embodiments of the present disclosure, a method may include providing a micro-optical component source wafer comprising a cavity adjacent to one or more anchor portions; placing at least a portion of a liquid curable polymer in the cavity; forming a structure (e.g., a micro-optical component), wherein forming the structure comprises using two-photon polymerization to cure only a portion of the liquid curable polymer to form at least a portion of the structure; forming an assembly ties between the structure and one of the one or more anchor portions; and removing an uncured portion of the liquid curable polymer (e.g., from the cavity).

According to an embodiment of the present disclosure, a method of manufacturing a system (e.g., a micro-optical system) may include: providing a micro-optical component source wafer, the micro-optical component source wafer including one or more sacrificial portions separated by one or more anchor portions; coating at least a portion of the one or more sacrificial portions with a liquid curable polymer; forming a structure (e.g., a micro-optical component), wherein forming the structure includes forming at least a portion of the structure (e.g., a micro-optical component) using imprint lithography; and forming an assembly tie between the micro-optical component and one of the one or more anchor portions.

According to an embodiment of the present disclosure, a method of manufacturing a system (e.g., a micro-optical system) may include: providing a micro-optical component source wafer, the micro-optical component source wafer including one or more sacrificial portions separated by one or more anchor portions; forming a mold in one of the one or more sacrificial portions; coating at least a portion of the sacrificial portions including the mold with a liquid curable polymer; forming a structure (e.g., a micro-optical component), wherein forming the structure includes curing the liquid curable polymer; and forming an assembly tie between the structure and one of the one or more anchor portions. The mold may be formed by etching a solid material in the sacrificial portion.

According to an embodiment of the present disclosure, a method of manufacturing a system (e.g., a micro-optical system) may include: providing a micro-optical component source wafer, the micro-optical component source wafer including a cavity adjacent to an anchor portion; forming a mold in the cavity using imprint lithography, wherein using imprint lithography includes coating the cavity with a liquid curable polymer and curing the liquid curable polymer; forming a structure (e.g., a micro-optical component), wherein forming the structure includes disposing a material in the mold that can be etched differentially from the mold; forming an assembly tie between the micro-optical component and one of the anchor portions; and etching the cured polymer to release the transferable structure. The cavity may be a sacrificial portion.

In some embodiments of the present disclosure, a micro-optical assembly includes a micro-substrate having a micro-substrate region and a micro-optical element disposed on the micro-substrate region of the micro-substrate. The micro-optical element may have a micro-optical element region above the micro-substrate, and the micro-substrate region may be larger than the micro-optical element region. According to embodiments of the present disclosure, the assembly ties may be formed in a common step with forming the structure (e.g., micro-optical assembly), or may be formed in additional deposition and processing (e.g., patterning) steps. In some embodiments, the component ties include ties portions formed in a common step with forming the structure, and include additional ties portions comprising different materials formed using additional deposition and processing (e.g., patterning) steps, for example to form hybrid ties comprising a plurality of different materials, such as organic (e.g., polymer) materials and inorganic (e.g., silicon oxide or nitride) materials.

The methods described herein can be used to fabricate micro-optical systems, but are not limited to such micro-optical systems and can be used, for example, to fabricate non-optical microsystems. In some embodiments, the structures of the present disclosure can be non-optical microcomponents, such as micro-transferable non-optical microcomponents having dimensions in the micrometer range (e.g., any combination of height, width, or length less than or equal to 250 μm, less than 250 μm, not more than 200 μm, not more than 150 μm, not more than 10 μm, not more than 75 μm, not more than 50 μm, not more than 25 μm, or not more than 10 μm).

In some embodiments, after printing the micro-optical component onto a component substrate, such as by microtransfer printing, the components of the present disclosure include a damaged (eg, cracked) or separated ligament.

Embodiments of the present disclosure provide micro-printable micro-optical components, systems, sources and methods useful for highly integrated optical and photonic systems.

Priority application

This application claims the benefit of U.S. Provisional Patent No. 63/414,423, filed on October 7, 2022, the disclosure of which is hereby incorporated by reference in its entirety.

Certain embodiments of the present disclosure provide, among other things, devices, structures, systems, and methods for micro-optical elements, micro-optical assemblies, and micro-optical systems. Micro-optical structures are useful for photonic systems such as photonic integrated circuits that combine electrical integrated circuits (e.g., silicon circuits such as CMOS) with optical emitters (e.g., light emitting diodes and lasers), optical sensors (e.g., photodiodes and phototransistors), optical amplifiers, optical modulators, and passive optical structures (e.g., reflectors such as mirrors, partial mirrors, diffusers, and prisms, refractors such as lenses, beam shaping optics, filters, frequency converters, and diverters such as gratings) that provide reflection, refraction, diversion, conversion, or filtering of photons, thereby redirecting, processing, or conditioning the photons. Embodiments of the present disclosure may also include optical waveguides or light pipes for transporting photons from one location to another. Photons propagating through free space (e.g., a vacuum or a gas such as atmosphere) or through a solid or liquid material with a constant optical index are also referred to herein as light, light, or beam. Processed or conditioned light is light (e.g., photons, light, or beam) whose direction, frequency, phase, frequency distribution, polarization, or propagation properties are changed, such as by reflection, refraction, conversion, filtering, or diffraction of an optical structure. Optical devices or structures interact with photons. Embodiments of the present disclosure provide micro-optical elements that are too small to be constructed using known methods and materials and are positioned in photonic systems, and therefore can be used to construct photonic systems that cannot be made using methods of the prior art.

Optical emitters, amplifiers, modulators, or sensors may include semiconductor components fabricated using fabrication facilities and materials (e.g., compatible with silicon fabrication facilities) with semiconductors such as silicon or compound semiconductors such as GaN, GaAs, or InP, or other photosensitive materials such as lithium niobate. Semiconductors may include active circuits or devices such as transistors, optical sensors, optical amplifiers, or optical light emitters such as lasers, light emitting diodes (LEDs), or photodiodes. In some embodiments, the devices, structures, and systems disclosed herein include a silicon substrate or a silicon substrate including a silicon circuit. Silicon circuits can be connected to non-silicon semiconductor components to make heterogeneous modules, such as light control circuits, light modulation circuits, or light response circuits for light emitters or light responders.

An optical structure that modulates light (such as a micro-optical element of the present disclosure) may include, for example, glass, a polymer, or silicon. The micro-optical element may be at least partially transparent (e.g., at least 50% transparent, at least 60% transparent, at least 70% transparent, at least 80% transparent, at least 90% transparent, or at least 95% transparent) to light of one or more desired frequencies (such as light modulated, generated, or sensed by a micro-optical element, light emitter, or light sensor of the present disclosure). The optical structure may include a plurality of layers or coatings disposed on one or more surfaces of the optical structure, such as an index matching coating, a reflective coating (such as a thin silver layer or aluminum layer), a phase change layer, a polarization sensitive layer, or an anti-reflection layer. The light may be, for example, visible light, infrared light, ultraviolet light, any electromagnetic radiation with a frequency between 300 GHz and 3000 THz or a wavelength of 10 nm to 1000 μm, and generally any electromagnetic wave of any frequency that can be or is intentionally modulated or otherwise processed with a micro-optical element. The substrate on which the one or more micro-optical elements are disposed may be at least partially transparent (e.g., transparent) to light of one or more desired frequencies (e.g., at least 50% transparent, at least 60% transparent, at least 70% transparent, at least 80% transparent, at least 90% transparent, or at least 95% transparent). In some embodiments, the substrate on which the one or more micro-optical elements are disposed may be at least partially reflective (e.g., reflective) to light of one or more desired frequencies (e.g., at least 50% reflective, at least 60% reflective, at least 70% reflective, at least 80% reflective, at least 90% reflective, or at least 95% reflective). In some embodiments, the substrate in which one or more micro-optical elements are disposed can be at least partially absorptive (e.g., opaque) to light of one or more desired frequencies (e.g., at least 50% absorptive, at least 60% absorptive, at least 70% absorptive, at least 80% absorptive, at least 90% absorptive, or at least 95% absorptive).

According to an embodiment of the present disclosure and as shown in FIGS. 1A to 1D , a micro-optical assembly 10 includes a micro-substrate 12 having a micro-substrate surface 13. A micro-optical element 14 structured to modulate light 50 may be disposed on the micro-substrate surface 13 of the micro-substrate 12. The micro-substrate surface 13 may also be a side of the micro-substrate 12 opposite to the micro-optical element 14, or may refer to two sides (e.g., opposite sides) of the micro-substrate 12, with the micro-optical element 14 disposed on or formed in at least one of the two sides. The micro-substrate surface 13 may be a side of the micro-substrate 12 on which the micro-optical element 10 is disposed, such as a side having a micro-transfer stamp 60 as discussed below. The micro-optical element 14 may be integral with the micro-substrate 12. The micro-optical element 14 may be adhered to the micro-substrate surface 13, for example, with an adhesive. In embodiments of the present disclosure, the micro-substrate 12 provides a structure that can be used to achieve micro-transfer, particularly where the micro-optical element 14 may be difficult to handle (e.g., manipulate, position, locate, or place) in an available microsystem. In some embodiments, the micro-substrate 12 has a thickness (or height) that is less than the thickness (or height) of the micro-optical element 14. In some embodiments, the micro-substrate 12 has a thickness (or height) of no greater than 20 μm, no greater than 10 μm, no greater than 5 μm, no greater than 4 μm, no greater than 2 μm, or no greater than 1 μm.

The micro-optical element 14 may be a passive optical structure that does not require external power (e.g., electricity). The micro-optical assembly 10 may include at least a portion of an assembly tether 11 that is physically attached to the micro-substrate 12 or physically attached to the micro-optical element 14. The assembly tether 11 may be damaged (e.g., broken) or separated. In a direction D orthogonal to the surface of the micro-substrate 12 on which the micro-optical element 14 is disposed, the micro-optical assembly 10 may have a thickness H (e.g., the height or depth of the micro-optical assembly 10) of not more than 250 μm (e.g., less than 250 μm, not more than 200 μm, not more than 150 μm, not more than 100 μm, not more than 75 μm, not more than 50 μm, not more than 25 μm, or not more than 10 μm). Micro-optical components 10 of this size or thickness cannot be easily or accurately microassembled into micro-optical systems using prior art techniques. Therefore, embodiments of the present disclosure enable accurate microassembly of large-volume micro-optical components 10 into smaller and less expensive photonic systems.

The micro-optical element 14 may have a micro-optical element area 18 on or above the micro-substrate surface 13. The micro-substrate surface 13 may have a micro-substrate area 16 that is larger than the micro-optical element area 18, as shown in FIG. 1B and FIG. 1D, so that the micro-substrate 12 extends beyond the micro-optical element 14 in a direction parallel to the micro-substrate surface 13 to form an extension to the micro-optical element 14, which can be used to hold the micro-optical element 14 in place or pick up or otherwise mechanically manipulate the micro-optical element 14 without touching the micro-optical element 14 itself (this can reduce the damage performance or damage to the micro-optical element 14 that may occur due to any mechanical manipulation of the micro-optical assembly 10 or contact with the micro-optical element 14). In some embodiments, the micro-substrate area 16 is equal to or smaller than the micro-optical element area 18. In some such embodiments, the micro-optical assembly 10 can be picked up, held, or manipulated by contacting the side of the micro-substrate 12 opposite the micro-optical element 14. The micro-substrate 12 can have a micro-substrate area 16 of no greater than 100,000 μm ² (e.g., no greater than 62,500 μm ² , less than 62,500 μm ² , no greater than 40,000 μm ² , less than 40,000 μm ² , no greater than 20,000 μm ² , no greater than 10,000 μm ² , no greater than 2,500 μm ² , no greater than 400 μm ² , or no greater than 100 μm ² ). In some embodiments, the micro substrate 12 has a large aspect ratio (length to width) of, for example, not less than 2: 1, not less than 4: 1, not less than 5: 1, not less than 8: 1, or not less than 10: 1. In some embodiments, the micro substrate 12 has a width of not more than 50 μm and a length of not less than 100 μm, 200 μm, 250 μm, or 500 μm, or a width of not more than 100 μm and a length of not less than 200 μm, 500 μm, 750 μm, or 1000 μm. In some embodiments, the microsubstrate 12 has a width of no greater than 200 μm and a length of no less than 400 μm, 600 μm, 800 μm, 1000 μm, 1200 μm, 1400 μm, 1600 μm, 1800 μm, or 2000 μm. A high aspect ratio microsubstrate 12 may be useful, for example, where the optically active element 20 (e.g., a microlaser) has a large aspect ratio or where the micro-optical element 14 has a large aspect ratio. Micro-optical components 10 having such small areas and/or large aspect ratios may be difficult or impossible to construct or assemble using prior art techniques. However, using the structures and methods of the present disclosure, such micro-optical components 10 may be integrated into a micro-optical system 70 (such as a photonic system or photonic integrated circuit), thereby providing reduced size and reduced cost with improved performance.

The micro-optical assembly 10 may include micro-alignment marks 15 (fiducial marks) disposed on or in the micro-substrate 12 to assist in aligning the micro-optical assembly 10 on the system substrate 40 in the micro-optical system 70, as will be discussed further below. The micro-substrate surface 13 may have a micro-substrate region 16 excluding the micro-optical element region 18, which absorbs or diffuses stray light 50, for example to reduce unwanted reflections in the micro-optical system 70. Such a region of the micro-substrate surface 13 may be black, for example coated with a material that absorbs light 50, such as carbon black. Thus, the micro-substrate 12 may have portions that are light transparent or light reflective and portions that are light absorptive (e.g., light absorbing or light absorbing). In some embodiments, the micro-substrate 12 may have portions that are light transparent and other portions that are light reflective. The patterned microsubstrate 12 may be fabricated, for example, by pattern-wise material deposition such as evaporation of light-reflecting or light-absorbing material using, for example, photolithography, painting or inkjet deposition methods.

In some embodiments of the present disclosure, in contrast to the micro-optical elements 14, the micro-substrate 12 may transmit but not intentionally condition (e.g., redirect or transform) light 50. In particular, in some embodiments, the micro-substrate areas 16 excluding the micro-optical element areas 18 are not intended to manipulate or otherwise condition the light 50, and in some embodiments, do not receive light 50. Those with knowledge of optical design will appreciate that any real-world system experiences ambient light 50 or unwanted light 50 reflections or propagation, and such light 50 may strike the micro-substrate areas 16 excluding the micro-optical element areas 18. To reduce these unwanted effects, the micro-substrate areas 16 excluding the micro-optical element areas 18 may absorb the light 50, for example, with a coating of a black material such as carbon black. In some embodiments, the micro-optical device region 18 of the micro-substrate 12 may be a portion of the micro-optical device 14 (eg, the micro-optical device 14 may include a portion of the micro-substrate 12 in the micro-optical device region 18 ).

In some embodiments of the present disclosure, in conjunction with micro-optical elements 14, microsubstrates 12 can condition (e.g., redirect or transform) light 50. For example, microsubstrates 12 can have a reflective coating 19 (or can be reflective, as shown in FIG. 7B ), can refract light 50, can include phosphors or dyes that filter light 50, can include phosphors or quantum dots that absorb and re-emit light 50 as optical frequency converters, or can include materials that affect the polarization of light 50 (e.g., polymers with aligned molecules). Microsubstrates 12 can have substantially parallel opposing sides (e.g., as shown) or can have non-parallel opposing sides. Microsubstrates 12 can have substantially flat sides (e.g., microsubstrate surfaces 13, as shown) or can have non-planar or structured sides.

The micro-optical element 14 may be a passive optical element that conditions light 50 (e.g., conditions light rays, beams, or photons 50 that intersect the micro-optical element 14 at an optical surface or face of the micro-optical element 14) by, for example, reflecting, partially reflecting, filtering, frequency converting, changing phase, changing polarization, refracting, or diffusing light 50 incident on the micro-optical element 14. The micro-optical element 14 may be a reflector, a partially reflector, or a diffraction grating and may be coated with an optical coating such as an anti-reflective coating to reduce unwanted optical effects, or may incorporate a passive optical material such as a filter or multiple layers that filters light 50 of a desired frequency through optical interference. In some embodiments, the micro-optical element 14 is a lens (e.g., a small lens with optical power) or a prism. In some embodiments, the micro-optical element 14 is a micro-lens, an array of micro-lenses, or includes a plurality of micro-lenses. In some embodiments, the micro-optical element 14 is an array of micro-optical components (e.g., micro-lenses or micro-diversion gratings). The micro-optical element 14 may include a coating of fluorescent or phosphorescent material to absorb and re-emit light 50. The micro-optical element 14 may change the phase or frequency distribution or both of the incident light 50. The micro-optical element 14 may be an optical filter. The micro-optical element 14 may focus or defocus the incident light 50. The micro-optical element 14 may be a Fresnel lens. In some embodiments, the micro-optical element 14 can redirect light 50 from a direction parallel to the micro-substrate surface 13 (horizontal) to a direction D (vertical) orthogonal to the micro-substrate surface 13, such as shown in FIG. 1C. In some embodiments, the light 50 conditioned by the micro-optical element 14 passes through the micro-substrate 12, and the micro-substrate 12 is substantially transparent to such light 50. For example, the micro-substrate 12 has a transparency of not less than 50%, 75%, 80%, 85%, 90%, or 95% to the light 50 conditioned by the micro-optical element 14 passing through the micro-substrate 12. In some embodiments, the light 50 conditioned by the micro-optical element 14 is substantially reflected by the micro-substrate 12, and the micro-substrate 12 is substantially reflective to such light 50. For example, the micro-substrate 12 has a reflectivity of not less than 50%, 75%, 80%, 85%, 90%, or 95% for light 50 incident on the micro-substrate 12 conditioned by the micro-optical element 14. In some embodiments, the micro-optical element 14 can redirect the light 50 from a direction parallel to the micro-substrate surface 13 to a different direction parallel to the micro-substrate surface 13, such as in an orthogonal direction parallel to the micro-substrate surface 13. In some embodiments, the micro-optical element 14 can reflect the incoming light 50 to a direction parallel to and opposite to the incoming light 50.

In the embodiments shown in Figures 1A-1D, the micro-substrate 12 extends beyond the micro-optical elements 14 in two dimensions X and Y parallel to the micro-substrate surface 13. In some embodiments and as shown in Figure 2, the micro-substrate 12 extends beyond the micro-optical elements 14 in only one dimension (direction X as shown) parallel to the micro-substrate surface 13. By providing the micro-substrate 12 with a micro-substrate surface 13 extension portion in only one dimension, the micro-optical assembly 10 can be more closely arranged together in a photonic system, for example, more closely arranged together in a direction orthogonal to the direction of the micro-substrate surface 13 extension portion.

1A-2 illustrate micro-optical elements 14 that can redirect light 50 propagating parallel to the microsubstrate surface 13 to a direction perpendicular to the microsubstrate surface 13, and vice versa . FIG. 3 illustrates micro-optical elements 14 that can redirect light 50 propagating parallel to the microsubstrate surface 13 to a different direction also parallel to the microsubstrate surface 13. In some such embodiments, the light 50 modulated by the micro-optical elements 14 propagates parallel to the microsubstrate 12, and the microsubstrate 12 is substantially opaque or absorbs this light 50 or ambient light or stray light 50. For example, the microsubstrate 12 can absorb not less than 50%, 75%, 80%, 85%, 90%, or 95% of the light 50 incident on the microsubstrate 12.

1A to 3 illustrate a micro-optical element 14 having a flat surface suitable for conditioning light 50 by reflection or refraction. FIGS. 4 and 5 illustrate a micro-optical element 14 having a curved surface suitable for a lens (e.g., a biconvex lens, a biconcave lens, a convex lens, or a concave lens). Such a curve can be spherical, aspherical, or have an arbitrary surface shape. Thus, the micro-optical element 14 can be a lens, such as a spherical lens, an aspherical lens, or a lens with an arbitrary surface shape. As shown in FIG. 4 , a biconcave lens is configured to condition (e.g., refract and focus) light 50 propagating parallel to the micro-substrate surface 13. As shown in FIG. 5 , a convex lens is configured to condition (e.g., focus) light 50 propagating perpendicular to the micro-substrate surface 13. The micro-optical element 14 of the present disclosure can focus, defocus, or randomly redistribute (eg, diffuse) the incident light 50. The micro-substrate 12 can be a diffuser.

In some embodiments and as shown in Figures 1A to 5, the micro-optical element 14 extends away from the micro-substrate 12 (e.g., above or below) in a direction normal to the micro-substrate surface 13. In some embodiments and as shown in Figure 6, the micro-optical element 14 does not extend away from the micro-substrate 12, but is instead integrated into the micro-substrate surface 13 to form a diffraction grating disposed on or in the micro-substrate surface 13 of the micro-substrate 12. In some embodiments, the micro-optical element 14 is a Fresnel lens.

7A and 7B illustrate a micro-optical assembly 10 of the present disclosure including a photoactive element 20, such as a light generating element (e.g., a laser, such as a vertical cavity surface emitting laser or a light emitting diode), a light responsive element (a photo sensor, such as a photodiode or a phototransistor), or a light modulating element (e.g., an optical amplifier or a modulator) disposed on a micro-substrate 12 on a side of the micro-substrate 12 opposite to the micro-optical element 14 (e.g., on a side of the micro-substrate 12 opposite to the micro-substrate surface 13). Such a photoactive element 20 can emit light 50 into the micro-optical element 14, sense light 50 propagating out of the micro-optical element 14, or modulate light 50 transmitted through the micro-optical element 14. The optically active element 20 may be disposed on the side of the micro-substrate 12 opposite the micro-optical element 14 after the micro-substrate 12 and the micro-optical element 14 are formed as described below, for example by micro-transferring from an optically active element source wafer to the micro-substrate 12 before or after micro-transferring the micro-optical assembly 10 from the micro-optical assembly source wafer 30 to the system substrate 40. Thus, the optically active element 20 may include or be attached to a damaged (e.g., cracked) or separated optically active element strap 21 (shown in FIGS. 7A and 7B). FIG. 7B illustrates a reflective coating 19 applied to the surface of the micro-optical element 14 to redirect light 50 received from or transmitted to the optically active element 20. The micro-substrate 12 may have substantially parallel and smooth opposite sides, for example forming a substrate, such as found in display substrates and semiconductor wafers. (In FIGS. 7A and 7B , the micro-optical element 14 is shown inverted with respect to FIGS. 1A to 5 for clarity.)

In some embodiments of the present disclosure, the microsubstrate 12 and the micro-optical element 14 are integral and unitary, e.g., comprise a single structure having different portions, may comprise the same material, may be the same material, or may be made from a common material in a common process (e.g., in one or more common manufacturing steps). The micro-optical assembly 10 may be monolithic. For example, in some embodiments, the micro-optical assembly 10 comprises a curable polymer, such as a photoresist, epoxy, or resin. In some embodiments, the microsubstrate 12 comprises a material different from the micro-optical element 14 and may be made at different times using different steps, or may comprise different structures made from different materials bonded together at different times at different locations, e.g., the micro-optical element 14 may be bonded to the microsubstrate surface 13 of the microsubstrate 12 using an optically clear adhesive. In some embodiments, the adhesive may be a metal, such as a reflective metal or solder. The microsubstrate 12 may have substantially parallel opposing sides (as shown) or may have non-parallel opposing sides. For example, in some embodiments, the microsubstrate 12 comprises a substantially transparent oxide, such as silicon dioxide, and the micro-optical element 14 comprises a curable polymer. In some embodiments, the microsubstrate 12 is not substantially transparent to light 50 and may comprise, for example, a ceramic or a light absorbing resin. One or both of the micro-substrate 12 and the micro-optical element 14 of the micro-optical assembly 10 can be made by injection molding, stamping, etching, two-photon polymerization, micro- or nano-imprinting, imprint lithography (e.g., nano-imprint lithography), or any of a variety of photolithographic processing steps, either alone or simultaneously, including but not limited to any one or a combination of spraying, spin coating, doctor blade coating, funnel coating, curtain coating, evaporation coating, sputtering, stripping, masking, etching, and curing.

8A-8D illustrate a micro-optical component source wafer 30 of a micro-optical component 10. As shown in FIGS. 8A-8D, the micro-optical component 10 can be constructed by providing a component source wafer 30 or substrate having a sacrificial portion 34 or a gap 36 separated by a fixture 32 (e.g., an anchoring portion 32 of the micro-optical component source wafer 30). If the sacrificial portion 34 is etched to form the gap 36, the micro-optical component 10 can be suspended above the gap 36 by a component strap 11 connected to the fixture 32. The micro-optical element 14 can extend in a direction away from the sacrificial portion 34 or the gap 36 (as shown in FIG. 8A), can extend into the sacrificial portion 34 or the gap 36 (as shown in FIGS. 8B and 8D), or both (as shown in FIG. 8C). In some embodiments, the micro-optical element 10 may use multiple micro-optical elements 14 disposed on a common micro-substrate 12 (e.g., as shown in FIG. 8C ) to steer or otherwise process multiple light beams 50. In some embodiments, the micro-optical element 10 may use a single common micro-optical element 14 disposed on a micro-substrate 12 to steer or otherwise process multiple light beams 50. FIG. 8D illustrates a micro-optical assembly 10 structure having a prism having a light reflecting surface for reflecting light 50 outside the prism through the micro-substrate 12.

In some embodiments, the micro-optical component 10 is coated with a material, such as a polymer or an inorganic oxide or nitride (such as silicon dioxide or silicon nitride), which can be etched differently from the material of the sacrificial portion 34 or the micro-optical component source wafer 30. For example, the material is processed using photolithographic methods and materials, including masking and etching or in some embodiments by cleaning. This method is particularly useful for inorganic materials, but can also be used for organic materials. In some embodiments, the material is applied in a liquid state, the material is photolithographically processed, and then the material is cured. (Liquid materials can be soft-cured before photolithographic processing.) In some embodiments, the material is applied in a liquid state, the material is shaped, and then the material is cured. The material can but is not necessarily soft-cured before shaping. Organic materials (e.g., polymers) may be shaped by microimprinting (micromolding) (e.g., using a master mold, such as a photolithographically constructed silicon master mold), followed by curing (with the mold in place or after removal of the mold), or shaped by two-photon polymerization to form micro-optical components 10. Micro-optical components 10 may be photolithographically processed after micromolding, for example to segment multiple micro-optical components 10 or to provide additional optical or protective coatings over the surface of the component source wafer 30. Additional layers may be patterned.

Once the micro-optical components 10 are constructed, they can be etched down by etching the sacrificial portions 34 to form gaps 36 and suspended above the gaps 36 and the component source wafer 30 by the component ties 11. In some embodiments, the micro-substrate 12 or micro-optical elements 14 can be etched differently from the material comprising the sacrificial portions 34. For example, the micro-substrate 12 or micro-optical elements 14 can include a layer of silicon dioxide or silicon nitride that is disposed and patterned over the sacrificial portions 34 and the component source wafer 30, and the sacrificial portions 34 can include a semiconductor such as silicon. The micro-optical element 14 is then formed, for example, by micro-imprinting and curing a polymer layer or curing a polymer layer using two-photon polymerization, and then encapsulating the micro-optical element to protect the cured polymer material from the sacrificial portion 34 etching process.

In some embodiments, the sacrificial portion 34 of the component source wafer 30 is photolithographically processed to form a physical structure (such as an indentation or pit, such as an inverted pyramid) such as a mold in the material of the sacrificial portion 34 (such as a material such as crystalline silicon). The structured surface of the sacrificial portion 34 is coated with the material of the micro-optical component 10, such as by sputtering, evaporation, spin coating, spray coating, or slit coating, and then shaped, such as by photolithographic processing or by micro-imprinting and curing, to build the micro-optical assembly 10 on the sacrificial portion 34. The sacrificial portion 34 is then etched so that the micro-optical component 10 is suspended above the sacrificial portion 34 and the component source wafer 30. Thus, depending on the construction method used, the micro-optical element 14 may extend from the micro-substrate 12 towards the micro-optical component source wafer 30 or away from the micro-optical component source wafer 30. The specific angle of the micro-optical element 14 relative to the micro-substrate 12 may therefore be defined by the crystalline properties of the sacrificial portion 34, for example due to the crystalline orientation of the (e.g., fast) etch plane relative to the crystalline orientation of the micro-optical component source wafer 30.

The micro-optical assembly 10 can be constructed in a variety of ways. In some embodiments of the present disclosure and as shown in Figures 9A-9D, cavities 42 separated by fixtures 32 are formed in the assembly source wafer 30, for example using photolithographic methods and materials, and are coated with a liquid uncured polymer 37 (e.g., by spin coating, spray coating, funnel or curtain coating, or using inkjet deposition pillars) to planarize the surface of the assembly source wafer 30 or at least coat or partially fill the cavities 42, as shown in Figure 9A. The uncured polymer 37 is then exposed to radiation 39 and cured, for example, using two-photon polymerization (e.g., direct laser writing), as shown in FIG. 9B , to cure the three-dimensional structure (e.g., cured polymer 38) to form a micro-optical assembly 10 having a micro-substrate 12, a micro-optical element 14, and an assembly ligament 11, as shown in FIG. 9C . The uncured polymer 37 is then washed (cleaned) away, as shown in FIG. 9D , to form a micro-optical element 10 attached to a fixture 32 with an assembly ligament 11 and suspended above a gap 36 in a cavity 42 in preparation for microtransfer. In some such embodiments, the micro-optical assembly 10 is unitary (e.g., monolithic) and comprises a single material and structure. This two-photon polymerization method can be used to construct any of the micro-optical components 10 structures shown in FIG. 8A to FIG. 8D .

In some embodiments of the present disclosure and as shown in Figures 10A to 10C, sacrificial portions 34 separated by fixtures 32 are formed in the component source wafer 30 (for example, using photolithography methods and materials) and coated with a liquid uncured polymer 37 (for example, by spin coating, spraying, funnel or curtain coating, or using an inkjet deposition device) to planarize the surface of the component source wafer 30 or at least coat or partially cover the sacrificial portions 34, as shown in Figure 10A. The uncured polymer 37 is then micro-imprinted (e.g., using imprint lithography with an imprint stamp 61), and the uncured polymer is cured, for example, using heat or radiation 39 (as shown in FIG. 9B ), to cure the three-dimensional structure (e.g., cured polymer 38) before or after removing the imprint stamp 61, thereby forming the micro-optical component 10 and component ties 11, as shown in FIG. 10C . In some embodiments, the uncured polymer 37 is first soft-cured before or during imprinting and before the final hard cure. The sacrificial portion 34 is then etched with an etchant, as shown in FIG. 10D , to form the micro-optical component 10 attached to the fixture 32 by the component ties 11 and suspended above the gap 36 in preparation for micro-transfer printing. In some such embodiments, micro-optical assembly 10 is unitary (e.g., monolithic) and comprises a single material and structure. The material of sacrificial portion 34 may be etched differently from cured polymer 38. In some embodiments, a protective or encapsulating coating may be disposed on sacrificial portion 34 (and optionally on fixture 32) or over cured polymer 38 to protect micro-optical assembly 10 from etchants.

11A-11D illustrate structures and methods similar to those of FIGS. 10-10D with a protective layer 35 (e.g., a capping layer) that protects the micro substrate 12 and micro-optical elements 14 from the etchant used to etch the sacrificial portion 34. For example, the protective layer 35 may be an inorganic material such as silicon dioxide or silicon nitride. A patterned layer of this material may be patterned over the sacrificial portion 34 and optionally the fixture 32 (as shown in FIG. 11A ). Before etching the sacrificial portion 34 to form the gap 36 (as shown in FIG. 11D ), the micro substrate 12 and the micro element 14 may be formed over the protective layer 35 (as shown in FIG. 11B ) and a patterned additional coating of the protective layer 35, which is disposed over the micro substrate 12 and the micro optical element 14 and protects both (as shown in FIG. 11C ). Although not shown in FIGS. 9A to 9C , in such embodiments, a protective layer 35 may also be provided to protect the micro substrate 12 and the micro optical element 14. The protective layer 35 may also provide structural integrity, such as making the micro substrate 12 and the micro optical element 14 strong, and provide a desired optical effect. In some such embodiments, the micro-optical component 10 is not necessarily unitary and may, for example, include different materials (eg, an inorganic protective layer 35 material and an organic or polymer material).

12A to 12E illustrate embodiments of the present disclosure that use a photolithographic process to form a mold in a component source wafer 30, and a micro-optical component 10 can be formed on the mold. As in the embodiment according to FIGS. 10A to 11D , sacrificial portions 34 separated by fixtures 32 are formed in the component source wafer 30, for example, using photolithographic methods and materials, as shown in FIG. 12A . The sacrificial portions 34 are then pattern-etched (e.g., using a patterned photoresist disposed on the sacrificial portions 34) to form a mold that is the inverse of the micro-optical element 14, as shown in FIG. 12B . An optional protective layer 35 can be disposed and patterned on the mold, as shown in FIG. 12E . A material (e.g., an inorganic material such as silicon dioxide or silicon nitride, an organic material such as a polymer) is disposed on the patterned sacrificial portion 34 (with or without a protective layer 35) and patterned to form at least a portion of the micro-optical component 10, as shown in FIG12C. The sacrificial portion 34 may then be etched to suspend the micro-optical component 10 above the gap 36 with the component ties 11 attached to the fixture 32. In some such embodiments, the micro-optical component 10 may be unitary (e.g., monolithic) and include a single material and structure, or may include additional different materials, such as a protective layer 35, as indicated in FIG12E. The material of the sacrificial portion 34 may be etched differently from the material of the micro-optical component 10. In some embodiments, the sacrificial portion 34 is a portion of the component source wafer 30 and may include a semiconductor material, such as silicon, which may be etched relative to the crystal plane of the component source wafer 30 to form a pattern.

In some embodiments and as shown in FIG. 12F , the mold may be constructed by coating the cavity 42 formed in the micro-optical component source wafer 30, such as that shown in FIG. 9A . The liquid uncured polymer 37 in the cavity 42 is then imprinted with an imprinting stamp 61 , the uncured polymer is cured, and the imprinting stamp 61 is removed to form the mold and sacrificial portion 34 as shown in FIG. 12B . The remainder of the steps shown in FIG. 12C and FIG. 12D may be performed as shown, except that the etching step (e.g., removal of the cured polymer 38 ) may use a different etchant. If the micro-optical component 10 includes the cured polymer 38 , the protective layer 35 may enable differential etching of the sacrificial portion 34 (cured portion 38 ).

According to an embodiment of the present disclosure, different two-photon polymerization, micro-imprinting and/or photolithography methods can be combined to form different micro-optical elements 14 in the micro-optical component 10 or different parts of the micro-optical component 10, for example, to form different micro-optical elements 14 in the micro-optical component 10 of Figure 8C, for example, first making the structure found in Figures 12A to 12C, then performing the steps shown in Figures 10A to 10C (or Figures 11A to 11C), and then performing the etching steps of Figures 9D, 10D, 11D and 12D.

In some embodiments, the assembly tape 11 may include only organic materials, for example, as shown in FIG. 10C , or only inorganic materials, for example, as shown in FIG. 11C . In some embodiments, the assembly tape 11 is a hybrid tape including both organic and inorganic materials, as shown in FIG. 13 . FIG. 13 illustrates a micro substrate 12 and an assembly tape 11 including a top inorganic layer coated on a bottom organic layer (or vice versa ). The hybrid assembly tape 11 may have improved fracture characteristics with fewer contaminating particles.

Those familiar with two-photon polymerization, microimprinting, and photolithography will appreciate that the methods described herein for fabricating micro-optical assemblies 10 are not limited in the different micro-optical structures that can be formed. In particular, a wide variety of micro-optical elements 14 can be constructed using these techniques. Furthermore, a variety of materials can be used in the micro-optical elements 14 of the present disclosure and coatings can be applied to the micro-optical elements. Non-optical micro-transferable components, devices, and structures can also be constructed using these techniques.

The position of the light beam 50 reflected or refracted from the surface of the micro-optical element 14 can be adapted by a correspondingly positioned optically active element 20 or a light transmission element such as a light pipe 44 (e.g., an optical waveguide) in a micro-optical system 70 including a micro-optical assembly 10, as shown in FIG. 14A. FIG. 14A illustrates a micro-optical assembly 10 disposed on a system substrate 40, for example, by microtransfer printing. The micro-optical element 14 of the micro-optical assembly 10 is disposed on the system substrate 40 and is aligned with and at least partially within a cavity 42 formed in the system substrate 40, for example, by pattern etching. The cavity 42 may have a plurality of cavity walls and a cavity floor. The micro-substrate 12 is disposed on a system substrate surface 43 of the system substrate 40, e.g., at least a portion of the micro-substrate region 16 of the micro-substrate 12 excluding the micro-optical element region 18 may be adhered to the system substrate surface 43 of the system substrate 40 with or without an adhesive. The micro-optical element 14 may be disposed in alignment with the optically active element 20 and light transmission structures, such as light pipes 44 formed in the system substrate 40, to optically guide light 50 to or from the optically active element 20 using the micro-optical element 14. The light pipe 44 may guide light 50 into or out of the micro-optical system 70 from an optical fiber cable 54 disposed in alignment with the light pipe 44 and the system substrate 40. In some embodiments, the optical fiber cable 54 is disposed in alignment with the light pipe 44 in the system substrate 40 (e.g., as shown in FIG. 14A ). In some embodiments, the optical fiber cable 54 is positioned to align with the light pipe 44 on the system substrate 40 (e.g., as shown in FIG. 14B ). In some embodiments, the optical fiber cable 54 is positioned to align with the light 50 propagating through free space on or above the system substrate 40 (e.g., as shown in FIG. 15 ).

FIG. 14B illustrates an embodiment in which the optically active element 20 is disposed in the cavity 42 of the system substrate 40 and light 50 is emitted to or received from a light pipe 44 on the system substrate surface 43 through the micro-optical element 14 of the micro-optical system 70. In some embodiments and as shown in FIG. 14B , the light 50 can be transmitted over the system substrate surface 43 through the light pipe 44 (e.g., a patterned silicon nitride waveguide) disposed on the system substrate surface 43. The light pipe 44 can be connected to the micro-optical element 14 with an optically clear or index matching adhesive 46. FIG. 14C illustrates an embodiment in which the micro-optical element 14 contacts, is directly adhered to, or is adhered with an adhesive to a side (e.g., a wall) of the cavity 42. Such placement of the micro-optical element 14 relative to the system substrate 40 (or a structure such as a light pipe 44 in or on the system substrate 40) can enhance the optical performance of the micro-optical system 70. FIG. 14D illustrates the micro-optical assembly 10 in the cavity 42 with the micro-substrate 12 adhered to the floor of the cavity 42 (e.g., with or without an adhesive), wherein the micro-optical element 14 extends above the system substrate surface 43. FIG. 14E illustrates the micro-optical assembly 10 in the cavity 42 with the micro-substrate 12 adhered to the floor of the cavity 42 (e.g., with or without an adhesive), wherein the micro-substrate surface 13 and the system substrate surface 43 are substantially parallel and in a common plane, e.g., within manufacturing constraints and tolerances.

In some embodiments and as shown in FIG15, light 50 may be transmitted through free space (e.g., the local environment) over system substrate surface 43 and may be conditioned by one or more micro-optical elements 14 and emitted or received by optically active elements 20 in micro-optical system 70. Optically active elements 20 may interact with microelectronic components 22 via electrodes 26 (e.g., photolithographically defined conductive wires) to respond to or use electrical signals to control optically active elements 20. In some embodiments and as shown in FIG14B, light 50 may propagate through light pipes 44 to and from micro-optical components 10 and optically active elements 20 disposed on system substrate 40, rather than through free space. The system substrate 40 may include micro-alignment marks 15 (fiducial marks) disposed on or in the system substrate 40 to help align the micro-optical component 10 with the system substrate 40 in the micro-optical system 70. (For clarity, the micro-optical component 10 is not shown with the micro-alignment marks 15 in all figures.) The micro-alignment marks 15 can be made using photolithography methods and materials, such as patterned and reflective or light-absorbing metal marks.

Additionally, in some embodiments, for the micro-optical system 70 and as shown in FIGS. 16A , 16B, and 14A-14C, light 50 may propagate to and from the micro-optical assembly 10 and the optically active element 20 through a light pipe 44 disposed in the system substrate 40. As shown in FIG. 16A , the micro-optical assembly 10 may include two or more micro-optical elements 14 disposed on a micro-substrate 12 and configured to condition light 50 from the cavity 42 and in free space disposed above the system substrate surface 43 (or through the light pipe 44). The micro-optical assembly 10 may include a plurality of lenses such as micro-lenses, or a plurality of reflectors such as micro-prisms, or one or more lenses and one or more reflectors. The micro-optical elements 14 in a common micro-optical assembly 10 may have different sizes, for example as shown in FIG. 16B . FIG. 16B illustrates a micro-optical assembly 10 having four micro-optical elements 14 (e.g., prisms), with two micro-optical elements 14 on each of two opposing sides of a micro-substrate 12. The micro-optical elements 14 on one side of a micro-substrate 12 may have a different size than the micro-optical elements 14 on the opposing side of the micro-substrate 12. In some embodiments, the multiple micro-optical elements 14 of a micro-optical assembly 10 may be considered as a single composite micro-optical element 14. The micro-optical assembly 10 may condition a single light beam 50 or multiple light beams 50, as shown in FIG. 16B . As shown in Figures 16B and 16C, the micro-optical component 10 having a single micro-substrate 12 may include two or more micro-optical components 14 disposed on the single micro-substrate 12, and optionally have two or more optically active elements 20 disposed on the single micro-substrate 12 on the side of the single micro-substrate 12 opposite to the micro-optical element 14.

The micro-optical element 14 can extend in a direction toward the system substrate 40 (e.g., into the system substrate 40) or away from the system substrate 40 (e.g., away from the system substrate surface 43 in direction D as shown in FIG. 1C). More generally, the light 50 can propagate through a waveguide (e.g., light pipe 44) in the system substrate 40, as shown in FIG. 14A, through a waveguide (e.g., light pipe 44) disposed on the system substrate 40 (e.g., through a light pipe 44 disposed on the system substrate surface 43), as shown in FIG. 14B, or through free space above the system substrate surface 43 in a direction that is parallel to the system substrate surface 43, as shown in FIG. 15, or orthogonal to the system substrate surface 43, as shown in FIGS. 14A-14D and 16A-16C. The micro-optical element 14 can redirect light 50 that is parallel to the system substrate surface 43, above or within the system substrate 40, or can redirect light 50 that is traveling parallel to the system substrate surface 43 to a direction orthogonal to the system substrate surface 43 (or vice versa ). In some embodiments and as shown in FIGS. 16A and 16B , the micro-optical element 14 can redirect light 50 that is propagating parallel to and above the system substrate surface 43 to light 50 that is propagating parallel to and within the system substrate 40. As shown in FIGS. 16D-16G and 16I-16K , the micro-optical element 14 in the common micro-optical assembly 10 can be or can include different types of micro-optical elements 14, for example, a lens coupled with a reflector such as a prism and disposed in a common optical path. FIG. 16D illustrates a convex lens and FIG. 16E illustrates a concave lens combined with a prism. The convex lens may be a light collimating or light collecting lens (e.g., an optical element) and the concave lens may be a diffusing or beam expanding lens (e.g., an optical element). In general, the micro-optical element 14 may be any beam shaping lens. FIG. 16F illustrates a micro-optical element 14 comprising an array of convex small lenses. FIG. 16G illustrates a micro-optical element 14 comprising an array of concave small lenses. FIG. 16H to FIG. 16K illustrate a micro-optical element 14 comprising a prism having a non-planar (e.g., non-flat) reflective (or refractive) surface for providing light collimation or beam shaping. The non-planar surface may also include a plurality of light shaping elements, such as micro-small lenses. FIG16H illustrates a micro-optical element 14 of a micro-optical assembly 10 including a prism with a non-planar surface in a cavity 42. FIG16I illustrates a micro-optical assembly 10 including a micro-optical element 14 that is a prism with an entirely planar surface on one side of a micro-substrate 12 in a cavity 42 and including a prism with a non-planar reflective surface on an opposite side of the micro-substrate 12 above a system substrate surface 43. FIG16J illustrates a micro-optical assembly 10 similar to FIG16I, except that the micro-optical element 14 prism with a non-planar reflective surface reflects light 50 in an opposite horizontal direction above the system substrate surface 43. FIG. 16K illustrates a micro-optical assembly 10 having both concave and convex microlenses that shapes light 50 from each prism using a flat reflective surface on the side of the micro-substrate 12 opposite the concave and convex microlenses. Typically, a light pipe 44 can transport (e.g., transmit) the light 50, for example, to an optical fiber cable 54, or in some embodiments to another micro-optical assembly 20 or a micro-optical system 70, for example, as shown in FIG. 15 and FIG. 16L. In FIG. 16L, for example, the optically active elements 20 are light emitters and light sensors. Typically, embodiments of the present disclosure can include a micro-optical assembly 10 that includes one or more different micro-optical elements 14 of different sizes and/or different types disposed in a common light 50 path. The micro-optical elements 14 may be disposed on a common side of the micro-substrate 12, on opposite sides of the micro-substrate 12, or both, for example, in the case where the micro-optical assembly 10 includes three, four, or more micro-optical elements 14, such as, for example, as shown in, for example, FIGS. 16A-16D . In some embodiments, the micro-optical assembly 10 includes three, four, or more micro-optical elements 14. In some embodiments, the micro-optical assembly 10 is structured to process, condition, redirect, or transform multiple light 50 beams, integrate multiple light 50 beams into a common light 50 beam, or split a light 50 beam into multiple independent light 50 beams.

In some embodiments, the cavity 42 may be filled or partially filled with a material, such as an optical index matching material, to reduce stray reflections from the surface of the cavity 42 or the micro-optical element 14. The optical index matching material may be a curable polymer that is disposed as a liquid in the cavity 42 before or after the micro-optical assembly 10 is disposed on the system substrate 40 and the micro-optical element 14 is disposed in the cavity 42 (e.g., as shown in FIG. 12A ), and then may be cured.

In various embodiments, the system substrate 40 may be a semiconductor (e.g., silicon or compound semiconductor), glass, polymer, resin, ceramic, sapphire, or a printed circuit board. The microelectronic components 22 disposed on the system substrate 40 may be integrated circuits, such as micro-transferred unpackaged bare dies, and may process electrical signals received from or provided to the optical active element 20. The microelectronic components 22 may be constructed on a silicon (or other semiconductor) wafer using a photolithography process. The optical active element 20 may be constructed using a photolithography process for a compound semiconductor wafer (e.g., InP, GaAs, GaN, and various alloys thereof).

Typically, the components of the present disclosure may be assembled using microtransfer printing to remove components (e.g., micro-optical components 10, optical active elements 20, and microelectronic components 22) from a component source wafer 30 and place the components on a system substrate 40, thereby destroying (e.g., breaking) or separating component ties 11 used to hold the components in place over an etched sacrificial portion 34 or cavity 42 (e.g., gap 36) of the component source wafer 30 to an anchoring portion (fixture 32) of the component source wafer 30. Microtransfer printing may be used to micro-assemble micron-scale components. For example, any of the micro-optical component 10, the optically active element 20, and the microelectronic component 22 may have a lateral extent of no more than two hundred µm, no more than one hundred µm, no more than fifty µm, no more than twenty µm, no more than ten µm, no more than five µm, no more than three µm, or no more than two µm above the system substrate surface 43, and a thickness of no more than one hundred µm, no more than fifty µm, no more than twenty µm, no more than ten µm, no more than five µm, no more than two µm, or no more than one micron.

17A to 20 illustrate methods and structures that may be used to construct embodiments of the present disclosure. In step 100, a source wafer is provided for each device in the micro-optical system 70, and in step 110, components (e.g., any one or more of the micro-optical components 10, the microelectronic components 22, and the optical active elements 20) are released from their source wafers (e.g., the micro-optical component source wafer 30). As shown in FIG. 17A, in step 120, a micro-transfer stamp 60 is provided and in step 130, the micro-transfer stamp is contacted to the component (e.g., the micro-optical component 10). The micro-transfer stamp 60 may include a stamp support 62 with a structured distal end, the stamp support contacting the micro-substrate 12, and optionally not contacting the micro-optical element 14, for example contacting the micro-substrate area 16 excluding the micro-optical element area 18, thereby avoiding possible damage to the micro-optical element 14. In step 140, as shown in FIG. 17B, the micro-transfer stamp 60 is used to remove the component (e.g., micro-optical component 10) from the component source wafer 30, thereby breaking or separating the component ties 11. As shown in FIG. 17C, a system substrate 40 is provided in step 160, and the component (e.g., micro-optical component 10) is placed on the system substrate 40 in step 170 using the micro-transfer stamp 60. 17D, the micro-transfer stamp 60 may then be removed in step 180 to construct the micro-optical system 70. Optionally, an adhesive layer is disposed on the system substrate 40 prior to micro-transfer printing the components to adhere the components to the system substrate surface 43. The adhesive layer may be cured after micro-transfer printing the components to the adhesive.

17A to 17D illustrate a process for microassembling the micro-optical component 10 onto the system substrate 40, wherein the micro-optical element 14 extends in a direction away from the system substrate 40. FIG. 18A to 18D illustrate similar steps and processes for microassembling the micro-optical component 10 onto the system substrate 40, wherein the micro-optical element 14 extends in a direction toward the system substrate 40, such as into and aligned with the cavity 42 of the system substrate 40. In this process, the distal ends of the stamp pillars 62 of the microtransfer stamp 60 need not be structured and can be planar, as shown in FIG. 18A to 18D, and can contact the side of the microsubstrate 12 opposite the micro-optical element 14.

In some embodiments, it may be desirable to construct a micro-optical element 14 that extends away from the component source wafer 30 (e.g., due to manufacturing constraints) and to position the micro-optical element on the system substrate 40 in the cavity 42. In some such embodiments, the micro-optical component 10 may be inverted (e.g., flipped) after picking up the micro-optical component 10 with the micro-transfer stamp 60 and before printing the micro-optical component 10 on the system substrate 40. This inversion may be accomplished using a stamp-to-stamp transfer. In such a transfer, the first micro-transfer stamp 60A is used to pick up the micro-optical component 10 from the component source wafer 30 (e.g., step 140 shown in FIG. 17B , for example, by contacting the micro-substrate surface 13 to the first stamp support 62A), and in an optional step 150, the second micro-transfer stamp 60B contacts the side of the micro-substrate 12 opposite the micro-substrate surface 13 to the second stamp support 62B to transfer the micro-optical component 10 from the first micro-transfer stamp 60A to the second micro-transfer stamp 60B, as shown in FIG. 19A . As shown in FIG. 19B , the first micro-transfer stamp 60A is removed, and in step 170, the second micro-transfer stamp 60B then contacts the micro-optical component 10 to the second stamp support 62B to adhere the micro-substrate surface 13 to the system substrate surface 43, as shown in FIG. 19C . Then, in step 180, the second micro-transfer stamp 60B is removed.

The micro-optical component 10 may be constructed in any of a variety of ways, examples of which are illustrated in FIGS. 10A-10D , 11A-11D , and 12-12F , and in the flow chart of FIG. 21 . Referring to these figures, a component source wafer 30, such as a semiconductor wafer, such as silicon or other substrate as known in the semiconductor and display industries, is provided in step 200 . Optionally, a cavity 42 is formed in the micro-optical component source crystal 30 in step 210 . In some embodiments, the cavity 42 is empty. In other embodiments, the cavity 42 is filled with a sacrificial material to form a sacrificial portion 34 . In some embodiments, the micro-optical component source wafer 30 is coated with a liquid material such as a polymer (e.g., a liquid curable and uncured polymer 37, such as a resin, epoxy, or photoresist) in step 220. The liquid uncured polymer 37 may be, but is not necessarily, soft-cured. Coating may be performed, for example, by spraying, spin coating, slit coating, funnel coating, or using an inkjet device. The micro-optical component source wafer 30 may be polarized by the coating of the liquid uncured polymer 37 and may fill any cavities 42, thereby forming a sacrificial portion 34. FIG. 9A illustrates an embodiment of filling the cavities 42 with the liquid uncured polymer 37 to form the sacrificial portion 34. 10A, 11A and 12A illustrate an embodiment in which the cavity 42 is filled with a solid sacrificial material to form the sacrificial portion 34. In the case of filling the cavity 42 with a solid sacrificial material, a protective layer 35 (eg, a transparent inorganic dielectric or a reflective metal) may be patterned over the sacrificial portion 34.

In step 230, the micro-optical element 14 or micro-substrate 12 (or both, included in the micro-optical assembly 10) is formed. In some embodiments, the micro-optical element 14 or micro-substrate 12 or both are formed using two-photon polymerization to cure the liquid uncured polymer 37 to produce a three-dimensional structure that forms a solid structure including the cured polymer 38, such as shown in FIG. 9B. One advantage of this technique is that the structure (e.g., the micro-optical element 14) can be formed in the cavity 42. In some embodiments, the micro-optical element 14 or micro-substrate 12 or both are formed using an imprint stamp 61 (e.g., using nanoimprint lithography) to form the three-dimensional structure in the liquid uncured polymer 37 above the assembly source wafer 30, and the liquid uncured polymer is cured to form a cured polymer 38 structure, such as shown in FIG. 10B and FIG. 11B. The three-dimensional structure may form any one or more of the micro-substrate 12, the micro-optical element 14, and the assembly ties 11. Where a protective layer 35 is present (shown in FIG. 11A ), the protective layer 35 may be patterned to form the assembly ties 11. The assembly ties 11 may include the protective layer 35, the cured polymer 38, or both. If desired and as shown in FIG. 11C , the protective layer 35 may also be disposed over the micro-optical element 14 and the micro-substrate 12 to protect both. The protective layer 35 may also provide optical benefits, such as a layer having an optical index different from that of the micro-optical element 14 or an anti-reflective layer. The protective layer 35 may include, for example, a plurality of layers including different materials or layers having different optical indices.

Once the liquid uncured polymer 37 is cured to form a three-dimensional cured polymer 38 structure, the sacrificial portion 34 can be removed in step 240 to form a gap 36, for example by cleaning (for example, when two-photon polymerization is used, as in Figure 9D) or by etching (when the sacrificial portion 34 includes a solid material, as in Figures 10D and 11D) to form a printed micro-optical component 10.

In some embodiments and as shown in Figures 12A-12D, in step 210 and as shown in Figure 12B, a pattern (e.g., a shape, depression, or pit) may be etched into the sacrificial portion 34. For example, the sacrificial portion 34 may include an anisotropically etchable material such as silicon and the etch plane is defined by the crystal structure of the sacrificial portion 34. As shown in Figure 12C, in step 230, the material of the micro-optical component 10 may be deposited in the pattern and over the sacrificial portion 34, such as a polymer that is subsequently cured in step 220, or in some embodiments, an inorganic material such as silicon dioxide or silicon nitride may be deposited and patterned. As shown in FIG. 12D , the sacrificial portion 34 may then be etched to form the gap 36 and provide the micro-optical assembly 10 ready for micro-transfer printing.

In some embodiments, the sacrificial portion 34 may be made by depositing a liquid curable polymer in the cavity 42 in the micro-optical component source substrate 30, such as in FIG. 9A. An imprinting stamp 61 may then be used to imprint the liquid curable polymer 37, such as in FIG. 12F, the curable polymer is cured, and the imprinting stamp 61 is removed to form the mold shown in FIG. 12B. If an inorganic material (such as silicon dioxide) is used to form the micro-optical component 10, the mold may be etched differentially from the micro-optical component 10 to release the micro-optical component 10. This method has the advantage of achieving mold structures (shapes) that are not easily constructed using photolithography and using component source wafer 30 materials that are not anisotropically etchable (such as glass). Thus, such methods provide micro-optical components 10 having a wide variety of shapes and using less expensive materials with less processing time.

The components (e.g., micro-optical components 10) transferred to the system substrate 40 are non-native to the system substrate 40. In embodiments where the system substrate 40 is a semiconductor (e.g., silicon), a circuit (e.g., a native microelectronic component 24 as shown in FIG. 15 ) can be constructed in or on the system substrate 40 and is native to the system substrate 40, rather than micro-transferred to the system substrate 40 as shown, which has the non-native microelectronic component 22 in FIG. 15 for processing electrical signals received from or provided to the optically active element 20.

As used herein, a device that is native to a substrate is formed on a substrate, for example, by photolithographic processing of a layer of material that is deposited directly on the substrate, for example, by sputtering or vapor deposition. Devices that are formed on a native substrate (e.g., component source substrate 30) and then transferred to a second substrate are non-native to the second substrate (e.g., system substrate 40).

Embodiments of the present disclosure provide apparatus and methods for microassembling heterogeneous components (e.g., micro-optical components 10, non-native microelectronic components 22, and optical active elements 20) that may all comprise materials different than the material of the system substrate 40. In some embodiments, the heterogeneous micro-optical system 70 comprises different materials, for example, different components comprising semiconductor materials, such as different compound semiconductor materials, such as GaAs, InP, GaN disposed on a common system substrate 40 (e.g., glass, ceramic, printed circuit board, or silicon). The system substrate 40 may include native semiconductor circuits. Using non-native materials enables the best material to be used for each component and avoids component photolithography processing incompatibilities.

Various embodiments of structures and methods are described herein, which include printed components such as micro-optical components 10 (e.g., made from such printed components). Printing may include or may be microtransfer printing. As used herein, microtransfer printing involves using a transfer device (e.g., a viscoelastic elastomer microtransfer stamp 60, such as a polydimethylsiloxane (PDMS) microtransfer stamp 60) to transfer a component using controlled adhesion. For example, an exemplary transfer device may use kinetic rate-dependent or shear-assisted control of adhesion between a transfer device (e.g., a microtransfer stamp 60) and a component (such as a micro-optical component 10). It is expected that in some embodiments, where the method is described as including microtransfer printing a component, there are other similar embodiments using different transfer methods. In methods according to some embodiments, a vacuum tool, an electrostatic tool or other transfer device is used to print the micro-optical assembly 10, for example by contacting the micro-substrate 12 in the micro-substrate area 16 excluding the micro-optical element area 18.

The system substrate 40 may be, for example, a module template for a module that may be micro-transferable. For example, printing (e.g., micro-transfer printing) and other processing (e.g., photolithography) may be used in combination to assemble and optically interconnect the micro-optical components 10 on the system substrate 40 to form a module, which may itself be transferred (e.g., printed, such as micro-transfer printed) to another larger target substrate. In some such embodiments where the system substrate 40 is a module substrate, the system substrate 40 may be native to a module source wafer. The system substrate 40 may then be released from the module source wafer by etching (e.g., using a gas or liquid etchant) (e.g., so that the system substrate is suspended from the module source wafer by strapping), followed by printing (e.g., using an elastomeric stamp). Figure 15 illustrates a configuration disposed on and in a system substrate 40 which may itself be a printable module.

In some embodiments, the micro-substrate 12 includes a micro-optical element 14 disposed therein. For example, the micro-substrate 12 and the micro-optical element 14 may be integral with each other.

In some embodiments, a stamp used to print the micro-optical assembly 10 is useful to avoid contact with structured pillars of a dedicated micro-optical element 14, which could damage the micro-optical element or otherwise impair the subsequent performance of the micro-optical element. For example, the stamp can have a suction cup configuration. In some embodiments, a micro-optical assembly 10 having micro-optical elements 14 extending from a micro-substrate 12 toward an assembly source wafer 30 allows the use of a stamp or other similar transfer device having unstructured pillars without the risk of damaging the micro-optical element 14.

Examples of microtransfer printing processes suitable for printing components onto the system substrate 40 are described in the following: U.S. Patent No. 8,722,458, entitled Optical Systems Fabricated by Printing-Based Assembly , U.S. Patent No. 9,362,113, entitled Engineered Substrates for Semiconductor Epitaxy and Methods of Fabricating the Same , U.S. Patent No. 9,358,775, entitled Apparatus and Methods for Micro-Transfer-Printing , U.S. Patent Application No. 14/822,868, entitled Compound Micro-Assembly Strategies and Devices , filed on August 10, 2015, and U.S. Patent No. 9,704,821, entitled Stamp with Structured Posts , each of which is hereby incorporated by reference in its entirety.

It is intended that the disclosed systems, apparatuses, methods, and processes cover variations and adaptations developed using the information from the embodiments described herein. Adaptations and/or modifications of the systems, apparatuses, methods, and processes described herein may be performed by one of ordinary skill in the relevant art.

Throughout the specification, where objects, devices, and systems are described as having, including, or comprising specific components, or where processes and methods are described as having, including, or comprising specific steps, it is intended that, in addition, there are objects, devices, and systems according to certain embodiments of the present disclosure that consist essentially of or consist of the enumerated components, and there are processes and methods according to certain embodiments of the present disclosure that consist essentially of or consist of the enumerated processing steps.

It should be understood that the order of steps or the order in which certain actions are performed is not important, as long as operability is not lost. In addition, two or more steps or actions can be implemented simultaneously.

Certain embodiments of the present disclosure are described above. However, it is expressly noted that the present disclosure is not limited to those embodiments, and additions and modifications to the contents expressly described in the present disclosure are also intended to be included in the scope of the disclosure. In addition, it should be understood that the features of the various embodiments described in the present disclosure are not mutually exclusive and may exist in various combinations and arrangements without departing from the spirit and scope of the disclosure, even if such combinations or arrangements are not clear enough. Certain implementations of inhomogeneous wafer structures, inhomogeneous semiconductor structures, methods of manufacturing such structures, and methods of using such structures have been described, and those generally familiar with this technology will now understand that other implementations that incorporate the concepts of the disclosure can be used. Therefore, the disclosure should not be limited to certain implementations, but should be limited only by the spirit and scope of the following patent application scope.

10: Micro-optical component 11: Component ties 12: Micro-substrate 13: Micro-substrate surface 14: Micro-optical component 15: Micro-alignment mark 16: Micro-substrate area 18: Micro-optical component area 19: Reflective coating 20: Optically active component 21: Optically active component ties 22: Micro-electronic component/non-native micro-electronic component 24: Native micro-electronic component 26: Electrode 30: Micro-optical component source wafer 32: Fixture/anchoring part 34: Sacrificial part/sacrificial material 35: Protective layer 36: Gap 37: Uncured polymer 38: Cured polymer 39: Radiation 40: System substrate 42: Cavity 43: System substrate surface 44: Light guide 46: Adhesive 50: Light/beam/light/photon 54: Optical fiber cable 60: Micro-transfer stamp 60A: First micro-transfer stamp 60B: Second micro-transfer stamp 61: Imprinting stamp 62: Stamp support 62A: First stamp support 62B: Second stamp support 70: Micro-optical system 100: Step of providing a component source wafer 110: Step of releasing a component from a component source wafer 120: Step of providing a stamp 130: Step of contacting a component with the stamp 140: Step of removing a component from a component source wafer using the stamp 150: Step of inverting the component using a stamp-to-stamp transfer 160: Step of providing a system substrate 170: Step of contacting the component to the system substrate using a stamp 180: Step of removing the stamp 200: Step of providing a component source wafer 210: Step of forming a cavity in the component source wafer 220: Step of coating the cavity and the component source wafer with a polymer 230: Step of curing the polymer pattern by pattern to form a micro-optical component 240: Step of cleaning uncured polymer/etching sacrificial portions D: Orthogonal direction H: Height/Thickness X: Dimension/Direction Y: Dimension/Direction

The drawings presented herein are for illustrative purposes only and not for limitation. The drawings are not necessarily drawn to scale. The foregoing and other objects, aspects, features, and advantages of the disclosure will become more apparent and better understood by reference to the following description in conjunction with the accompanying drawings, in which: According to an illustrative embodiment of the disclosure, FIG. 1A is a perspective view of a micro-optical assembly, FIG. 1B is a plan view of the micro-optical assembly, and FIG. 1C is a cross-section of the micro-optical assembly; According to an illustrative embodiment of the disclosure, FIG. 1D is a plan view of the area of the micro-substrate and micro-optical elements corresponding to FIGS. 1A to 1C; According to an illustrative embodiment of the disclosure, FIG. 2 is a perspective view of a micro-optical assembly; According to an illustrative embodiment of the disclosure, FIG. 3 is a perspective view of a reflective or refractive micro-optical assembly; According to an illustrative embodiment of the present disclosure, FIGS. 4 and 5 are perspective views of a refractive micro-optical assembly; According to an illustrative embodiment of the present disclosure, FIG. 6 is a perspective view of a diffractive micro-optical assembly; According to an illustrative embodiment of the present disclosure, FIG. 7A is a perspective view of a micro-optical assembly including an optically active element and FIG. 7B is a cross-section of the micro-optical assembly; According to an illustrative embodiment of the present disclosure, FIGS. 8A to 8D are cross-sections of a micro-optical assembly source wafer having different released micro-optical assemblies suspended above an etched sacrificial layer defining a gap; According to an illustrative embodiment of the present disclosure, FIGS. 9A to 9D are sequential cross-sections of a structure illustrating steps for constructing a micro-optical component source wafer having a released micro-optical component suspended above a gap using two-photon polymerization; According to an illustrative embodiment of the present disclosure, FIGS. 10A to 10D are sequential cross-sections of a structure illustrating steps for constructing a released micro-optical component suspended above an etched sacrificial layer defining a gap on a component source wafer using nanoimprint lithography; According to an illustrative embodiment of the present disclosure, FIGS. 11A to 11D are sequential cross-sections illustrating steps for constructing a released micro-optical component with a protective layer on a component source wafer; According to an illustrative embodiment of the present disclosure, FIGS. 12A to 12D are sequential cross-sections of structures illustrating steps for constructing a released micro-optical component on a component source wafer using a mold; According to an illustrative embodiment of the present disclosure, FIG. 12E is a cross-section illustrating a mold coated with a protective layer in a sacrificial layer of a component source wafer; According to an illustrative embodiment of the present disclosure, FIG. 12F is a cross-section illustrating the formation of a mold in a sacrificial layer of a component source wafer using imprint (e.g., nanoimprint) lithography; According to an illustrative embodiment of the present disclosure, FIG. 13 is a cross-section of a micro-optical assembly and a hybrid ligament on a sacrificial portion of a component source wafer; According to an illustrative embodiment of the present disclosure, FIG. 14A is a cross-section of a micro-optical system including a micro-optical assembly having a micro-optical element at least partially located in a cavity in a system substrate; According to an illustrative embodiment of the present disclosure, FIG. 14B is a cross-section of a micro-optical system including a micro-optical assembly having an optically active element at least partially located in a cavity in a system substrate and a micro-optical element above the cavity; According to an illustrative embodiment of the present disclosure, FIG. 14C is a cross-section of a micro-optical system including a micro-optical assembly having a micro-optical element at least partially located in a cavity in a system substrate and contacting or adhering to a wall of the cavity; According to an illustrative embodiment of the present disclosure, FIG. 14D is a cross-section of a micro-optical system including a micro-optical assembly having a micro-optical element at least partially located in a cavity in a system substrate and contacting or adhering to a bottom plate of the cavity; According to an illustrative embodiment of the present disclosure, FIG. 14E is a cross-section of a micro-optical system including a micro-optical component having a micro-substrate at least partially located in a cavity in a system substrate and contacting or adhering to a bottom plate of the cavity; According to an illustrative embodiment of the present disclosure, FIG. 15 is a perspective view of a micro-optical system such as a photonic integrated circuit; According to an illustrative embodiment of the present disclosure, FIGS. 16A to 16L are cross-sections of a micro-optical system; According to an illustrative embodiment of the present disclosure, FIGS. 17A to 17D are cross-sections of a continuous structure when constructing a micro-optical system; According to an illustrative embodiment of the present disclosure, FIGS. 18A to 18D are cross-sections of a continuous structure when constructing a micro-optical system; According to an illustrative embodiment of the present disclosure, FIGS. 19A to 19C are cross-sections of a continuous structure when constructing a micro-optical system using stamp-to-stamp transfer; and FIGS. 20 and 21 are flow charts of an illustrative embodiment of the present disclosure.

10: Micro-optical components

11: Assembly straps

12: Micro substrate

13: Micro substrate surface

14: Micro-optical components

15: Micro-alignment mark

Claims (45)

A micro-optical assembly comprising: a micro-substrate; a micro-optical element disposed on the micro-substrate; and at least a portion of an assembly tether, the at least a portion of the assembly tether being physically attached to the micro-substrate or physically attached to the micro-optical element, wherein the micro-optical assembly has a thickness of not more than 250 µm (e.g., not less than 250 µm, not more than 200 µm, not more than 150 µm, not more than 100 µm, not more than 75 µm, not more than 50 µm, not more than 25 µm, or not more than 10 µm). A micro-optical component as claimed in claim 1, wherein the component strap is a damaged (e.g., cracked) or detached component strap. A micro-optical assembly as claimed in claim 1 or claim 2, wherein the micro-substrate extends beyond the micro-optical element in only one dimension. A micro-optical assembly as claimed in any preceding claim, wherein the micro-substrate extends beyond the micro-optical element in two dimensions. A micro-optical assembly as claimed in any of the preceding claims, wherein the micro-optical element is a reflective element, a refractive element, a diffractive element, a frequency filter, a phase change element, a polarization detector element, a polarization modulator element, a frequency converter or any combination thereof. A micro-optical assembly as claimed in any of the preceding claims, wherein the micro-optical element is formed in the micro-substrate. A micro-optical assembly as claimed in any of the preceding claims, wherein the micro-optical element extends away from the micro-substrate in a direction perpendicular to a surface of the micro-substrate. A micro-optical component as claimed in any of the preceding claims, comprising a light generating element or a light responding element, wherein the light generating element or the light responding element is disposed on the micro-substrate on a side of the micro-substrate opposite to the micro-optical element. A micro-optical assembly as claimed in any preceding claim, wherein the light generating element is a laser or a light emitting diode and the light responsive element is a photodiode. A micro-optical assembly as claimed in any of the preceding claims, wherein the micro-substrate comprises a micro-alignment mark disposed in a micro-substrate region excluding a micro-optical device region. A micro-optical assembly as claimed in any of the preceding claims, wherein the micro-substrate is substantially transparent to light modulated by the micro-optical element. A micro-optical assembly as claimed in any of the preceding claims, wherein the micro-substrate is substantially opaque to, reflects, filters or absorbs light modulated by the micro-optical element. A micro-optical assembly as claimed in any of the preceding claims, wherein the micro-substrate and the micro-optical element are unitary (eg, monolithic and comprise a common material formed in a common step). A micro-optical assembly as claimed in any of the preceding claims, wherein the micro-substrate and the micro-optical element comprise different materials, or wherein the micro-substrate and the micro-optical element comprise different structures bonded together. A micro-optical component as claimed in any of the preceding claims, wherein (i) the microsubstrate has a microsubstrate area of no greater than 100,000 µm ² (e.g., no greater than 62,500 µm ² , less than 62,500 µm ² , no greater than 40,000 µm ² , less than 40,000 µm ² , no greater than 20,000 µm ² , no greater than 10,000 µm ² , no greater than 2,500 µm ² , no greater than 400 µm ² , or no greater than 100 µm ² ), (ii) the microsubstrate has a large aspect ratio (length to width) (e.g., no less than 2:1, no less than 4:1, no less than 5:1, no less than 8:1, or no less than 10:1), (iii) (a) the microsubstrate has a microsubstrate area of no greater than 50 (a) the micro substrate has a width of no more than 100 µm and a length of no less than 100 µm (e.g., no less than 200 µm, 250 µm or 500 µm), (b) the micro substrate has a width of no more than 100 µm and a length of no less than 500 µm (e.g., no less than 750 µm or 1000 µm), or (c) the micro substrate has a width of no more than 200 µm and a length of no less than 400 µm (e.g., no less than 600 µm, 800 µm, 1000 µm, 1200 µm, 1400 µm, 1600 µm, 1800 µm or 2000 µm), or (iv) both (i) and (ii). A micro-optical component as claimed in any of the preceding claims, comprising a protective layer or multiple protective layers. A micro-optical component as claimed in claim 16, wherein the protective layer or layers are constructed to interact with light as desired. A micro-optical component as claimed in claim 16 or claim 17, wherein the component strap includes a portion of the protective layer. A micro-optical component as claimed in any preceding claim, wherein the component ties are a hybrid organic-inorganic ties. A micro-optical system, comprising: a system substrate; and a micro-optical component according to any one of claims 1 to 19, the micro-optical component being disposed on the system substrate, wherein the micro-optical component is non-native to the system substrate. A micro-optical system as claimed in claim 20, wherein the micro-optical element extends in a direction away from the system substrate. A micro-optical system as claimed in claim 20 or claim 21, wherein the micro-optical system comprises a waveguide or a light pipe, which is disposed on or in the system substrate and is optically connected to the micro-optical element. A micro-optical system as in any one of claims 20 to 22, wherein the system substrate comprises a cavity and the micro-optical element is at least partially disposed in the cavity. A micro-optical system as in any one of claims 20 to 23, the micro-optical system comprising a light pipe disposed in or on the system substrate, the light pipe being arranged to transmit light entering or leaving the micro-optical element. A micro-optical system as in any of claims 20 to 24, wherein the system substrate includes a micro-alignment mark disposed on or in a surface of the system substrate. A micro-optical system as claimed in claim 25, wherein the micro-alignment mark disposed on or in the surface of the system substrate is aligned with an alignment mark disposed in or on the micro-substrate outside the micro-optical element area. A micro-optical system as in any one of claims 20 to 26, wherein the system substrate comprises a cavity and the micro-optical element is at least partially disposed in the cavity. A micro-optical system as in claim 27, wherein the cavity has one or more cavity sides extending into the system substrate, and the micro-optical element is arranged to contact one or more of the cavity sides. A micro-optical system as in any one of claims 20 to 28, wherein the system substrate comprises a cavity and the micro-substrate is at least partially disposed in the cavity. A micro-optical system as in claim 29, wherein the cavity has one or more cavity sides extending into the system substrate, and the micro-optical substrate is positioned to contact one or more of the one or more cavity sides. A micro-optical system as in any one of claims 27 to 30, the micro-optical system comprising an optical index matching material disposed in the cavity or an adhesive disposed in the cavity for adhering the micro-optical element to a surface of the cavity. A micro-optical system as in any one of claims 20 to 31, comprising an adhesive disposed in the cavity for adhering the micro-substrate to a surface of the cavity. A micro-optical system as in any one of claims 20 to 32, wherein a surface of the micro substrate and a surface of the system substrate are substantially in a common plane. A micro-optical system as claimed in any one of claims 20 to 33, the micro-optical system comprising a light generating element or a light response element, the light generating element or the light response element being disposed on the micro-substrate on a side of the micro-substrate opposite to the micro-optical element, wherein the system substrate is a semiconductor substrate, and wherein the semiconductor substrate comprises an electronic circuit electrically connected to the light generating element or the light response element. A micro-optical system as in any one of claims 20 to 34, wherein the system substrate includes a structural stopper disposed on a surface of the system substrate, and the micro-optical component contacts or adheres to the structural stopper. A micro-optical system as claimed in any one of claims 20 to 35, wherein the micro-optical system is a photonic integrated circuit. A micro-optical component source wafer, the micro-optical component source wafer comprising: a source wafer, the source wafer comprising one or more sacrificial portions separated by one or more anchoring portions; and a micro-optical component according to any one of claims 1 to 19, the micro-optical component being disposed completely and directly over each of the one or more sacrificial portions and attached to one of the one or more anchoring portions by at least a portion of an assembly strap. A method for manufacturing a micro-optical system, the method comprising: providing a micro-optical component source wafer according to claim 37; providing a stamp; providing a system substrate; contacting the stamp to the micro-optical component; removing the micro-optical component from the micro-optical component source wafer with the stamp; contacting the micro-optical component to the system substrate with the stamp; and removing the stamp from the micro-optical component and the system substrate. A method for manufacturing a micro-optical system, the method comprising: providing a micro-optical component source wafer according to claim 37; providing a first stamp and a second stamp; providing a system substrate; bringing the first stamp into contact with a first side of the micro-optical component; removing the micro-optical component from the micro-optical component source wafer with the first stamp; bringing the micro-optical component into contact with a second side of the micro-optical component opposite to the first side with the second stamp; bringing the first side of the micro-optical component into contact with the system substrate with the second stamp; and removing the second stamp from the micro-optical component and the system substrate. A method of manufacturing a micro-optical system, the method comprising: providing a micro-optical component source wafer, the micro-optical component source wafer comprising one or more sacrificial portions separated by one or more anchor portions; coating at least a portion of the one or more sacrificial portions with a liquid curable polymer; forming a structure (e.g., a micro-optical component), wherein forming the structure comprises using two-photon polymerization to cure only a portion of the liquid curable polymer to form at least a portion of the structure; forming an assembly tie between the structure and one of the one or more anchor portions; and removing an uncured portion of the liquid curable polymer. A method of manufacturing a micro-optical system, the method comprising: providing a micro-optical component source wafer, the micro-optical component source wafer comprising a cavity adjacent to one or more anchor portions; placing at least a portion of a liquid curable polymer in the cavity; forming a structure (e.g., a micro-optical component), wherein forming the structure comprises using two-photon polymerization to cure only a portion of the liquid curable polymer to form at least a portion of the structure; forming an assembly tie between the structure and one of the one or more anchor portions; and removing an uncured portion of the liquid curable polymer (e.g., from the cavity). A method of manufacturing a micro-optical system, the method comprising: providing a micro-optical component source wafer, the micro-optical component source wafer comprising one or more sacrificial portions separated by one or more anchoring portions; coating at least a portion of the one or more sacrificial portions with a liquid curable polymer; forming a structure (e.g., a micro-optical component), wherein forming the structure comprises forming at least a portion of the structure using imprint lithography; and forming an assembly tie between the structure and one of the one or more anchoring portions. A method of manufacturing a micro-optical system, the method comprising: providing a micro-optical component source wafer, the micro-optical component source wafer comprising one or more sacrificial portions separated by one or more anchoring portions; forming a mold in one of the one or more sacrificial portions; coating at least a portion of the sacrificial portions including the mold with a liquid curable polymer; forming a structure (e.g., a micro-optical component), wherein forming the structure comprises curing the liquid curable polymer; and forming an assembly tie between the structure and one of the one or more anchoring portions. A method of manufacturing a micro-optical system, the method comprising: Providing a micro-optical component source wafer, the micro-optical component source wafer comprising a cavity adjacent to an anchor portion; Using imprint lithography to form a mold in the cavity, wherein using imprint lithography comprises coating the cavity with a liquid curable polymer and curing the liquid curable polymer; Forming a structure, wherein forming the structure comprises placing a material in the mold that can be etched differentially from the mold; Forming an assembly tie between the micro-optical component and one of the anchor portions; and Etching the cured polymer to release the transferable structure. A micro-optical component, the micro-optical component comprising: a micro-substrate, the micro-substrate having a micro-substrate area; and a micro-optical element, the micro-optical element being disposed on the micro-substrate, wherein the micro-optical element has a micro-optical element area above the micro-substrate, and the micro-substrate area is larger than the micro-optical element area.