WO2024139560A1 - Silicon carbide stripping film based on laser cracking, and processing method and laser stripping system - Google Patents

Abstract

The present invention relates to the technical field of silicon carbide cutting. Provided are a silicon carbide stripping film based on laser cracking, and a processing method and a laser stripping system. The processing method comprises: S01, detecting a (0001) crystal face of a silicon carbide crystal ingot to obtain crystal face position information; S02, calculating an included angle between the crystal face position information and a first plane, and determining whether the included angle meets the requirement for a preset included angle; S03a, if so, starting a first laser beam to scan the silicon carbide crystal ingot, so as to form a face to be stripped that contains a plurality of cracks and extends along the first plane; S03b, if not, adjusting the angle of the silicon carbide crystal ingot and/or the angle of a first direction, and returning to step S02 until the included angle meets the requirement for the preset included angle; and S04, applying vibration to the face to be stripped, so as to obtain the silicon carbide stripping film. The processing method provided in the present invention can reduce stress and material loss of the silicon carbide stripping film, and improve the quality of the silicon carbide stripping film.

Description

Silicon carbide peeling sheet based on laser cracking, processing method and laser peeling system Technical Field

The present invention relates to the field of silicon carbide cutting technology, and in particular to a silicon carbide stripping sheet based on laser cracking, a processing method and a laser stripping system, and in particular to a processing method for a stripping sheet for a silicon carbide wafer having a size of not less than 8 inches.

Background technique

With the development of the industry, the performance requirements for components are getting higher and higher, gradually approaching the physical limit of silicon materials. Due to its excellent physical properties, silicon carbide substrates have incomparable advantages over Si materials in the fields of high voltage, high frequency, and high temperature. Currently, they are widely used in power electronics, microwave radio frequency devices, and high-end lighting.

The Mohs hardness of silicon carbide crystal is 9.2, second only to diamond. Its physical and chemical properties are extremely stable. It is a typical hard and brittle material. Ultra-precision processing has always been a difficult problem faced by the industry. The current status of the industry is that domestic 6-inch is in the mass production stage, 8-inch is in the research and development stage, foreign 6-inch has been mass-produced, and 8-inch is in the small-batch stage. 8 inches is bound to be the trend of future development. At present, small-batch production of 8-inch substrates has been achieved internationally, and domestic substrate manufacturers are also conducting research and development of 8-inch silicon carbide substrates. As the size expands to 8 inches, processing problems become more prominent, which seriously restricts the industrialization development of substrates.

The existing technology is to use mechanical cutting, mainly using mortar multi-wire cutting and diamond wire multi-wire cutting. The abrasives involved in the processing are different in these two methods, one is free abrasive cutting and the other is fixed abrasive processing, but they are essentially the same, both are physical contact cutting methods.

However, these two cutting methods also have some problems: as the size increases, the longitudinal cutting contact area becomes larger and larger, the cutting force per unit area that the abrasive can provide decreases, and greater deformation stress will be generated during the processing.

Invention patent CN110010519A "A Silicon Carbide Crystal Laser Slicing Device and Method" proposes to focus a pulsed laser inside the ingot, and then form a modified layer at the focus, and then separate the wafer from this modified layer. This method can not only improve processing efficiency, but also greatly reduce material waste. However, in the entire processing process of this invention, the time for platform acceleration and deceleration occupies a large part. At the same time, frequent acceleration and deceleration may also cause the ingot processed on the platform to be unstable due to inertia, which affects the depth of the laser focus in the ingot, resulting in inconsistent height of the modified layer formed, and ultimately resulting in poor thickness uniformity of the wafer. In the acceleration and deceleration stage, the laser energy may be insufficient or excessive, which may affect the degree of modification of the modified layer and the success rate of subsequent wafer separation.

Invention patent CN114473188A "A laser processing method and device for wafer stripping" discloses that a modified layer is formed by scanning the silicon carbide ingot through rotational motion of the silicon carbide ingot and laser scanning line motion. The motion trajectory of the laser modification is no longer a reciprocating broken line inside the crystal, which reduces the time wasted by motor acceleration and deceleration during the broken line motion, improves processing efficiency, and processes the interior and edge of the crystal in different areas through two laser heads, so that the modified layers inside and on the edge are on the same horizontal plane, thereby ensuring the thickness consistency within the wafer. However, the invention cannot automatically adjust the angle between the laser head and the silicon carbide ingot during the stripping process. Manual adjustment is required after each stripping, which increases the processing time and easily causes material loss and processing stress. Processing stress can lead to cracking in subsequent processing, as well as problems of excessive bending and warping. Therefore, it is imperative to reduce processing stress.

Summary of the invention

The inventors have found through analysis that the traditional technical solution is to process the crystal into a cylindrical crystal rod through a surface grinder and a cylindrical grinder, and then obtain the cutting piece through multi-wire cutting (the crystal is cut through a uniformly spaced wire mesh), and obtain the polished piece through edge chamfering, multi-piece grinding, mechanical polishing, and multi-piece chemical mechanical polishing, and finally clean and package the multi-piece to produce a ready-to-use silicon carbide single crystal substrate. This method is suitable for the processing of silicon carbide substrates below 6 inches. At present, the main problems faced by the processing of silicon carbide substrates above 8 inches are large substrate processing stress, large SFQR value, large changes in the front and back profiles (bow and Sori) of the epitaxy, and surface metal contamination, which seriously restrict the industrialization of the substrate.

In view of the defects existing in the prior art, the purpose of the present invention is to provide a silicon carbide peeling sheet and a processing method and a laser peeling system based on laser cracking, which can reduce the stress and material loss of the silicon carbide peeling sheet and improve the quality of the silicon carbide peeling sheet.

In a first aspect, the present invention provides a method for processing a silicon carbide peeling sheet based on laser cracking, the method comprising the following steps:

S01, detecting the (0001) crystal plane of the silicon carbide ingot to obtain crystal plane position information;

S02, calculating the angle between the crystal plane position information and the first plane, and judging whether the angle meets the requirement of a preset angle, wherein the first plane is always perpendicular to the first direction where the first laser beam is located;

S03a, if satisfied, start the first laser beam to scan the silicon carbide ingot to form a to-be-peeled surface containing multiple cracks and extending along the first plane; S03b, if not satisfied, adjust the angle of the silicon carbide ingot and/or the angle of the first direction, and return to step S02 until the angle value meets the requirement of the preset angle value;

S04, applying vibration to the surface to be peeled off to obtain a silicon carbide peeling sheet.

In a second aspect, the present invention provides a silicon carbide peeling sheet larger than 8 inches, with Bow≤60μm, Sori≤100μm, a damage layer depth≤100μm and a maximum surface crack step height not exceeding 70% of the damage layer depth.

In a third aspect, the present invention provides a system for preparing a silicon carbide substrate larger than 8 inches by laser stripping, comprising: a laser stripping device, including a crystal plane detection unit, an angle determination unit, an angle adjustment unit, a laser scanning unit, an external force application unit, and a fixing unit for fixing and supporting a silicon carbide ingot,

The crystal plane detection unit is arranged above the position to be peeled off of the silicon carbide ingot, and can detect the (0001) crystal plane of the silicon carbide ingot to obtain the crystal plane position information; the angle determination unit is arranged to receive the crystal plane position information, calculate the angle value between the crystal plane position information and the first plane, and judge whether the angle value meets the requirement of the preset angle value, if so, output a first signal, if not, output a second signal, wherein the first plane is always perpendicular to the first direction where the first laser beam is located; the angle adjustment unit includes a crystal unit capable of adjusting the angle of the silicon carbide ingot an ingot angle adjustment mechanism and/or a first laser beam angle adjustment mechanism capable of adjusting a first direction, and configured to receive a second signal and start the ingot angle adjustment mechanism and/or the first laser beam angle adjustment mechanism; the laser scanning unit comprises a first laser head capable of generating the first laser beam, and configured to receive the first signal and start the first laser head to scan the silicon carbide ingot to form a to-be-peeled surface containing a plurality of cracks and extending along the first plane; the external force applying unit is configured to apply vibration to the to-be-peeled surface to obtain a silicon carbide peeling sheet;

A thinning device having a grinding mechanism capable of thinning at least a portion of a single side of a single peeling sheet and/or thinning at least a portion of another single side of the single peeling sheet;

A polishing device, comprising a workbench and an i-th polishing mechanism connected in series through the workbench, wherein the i-th polishing mechanism comprises an i-th polishing assembly, an i-th liquid supply assembly, an i-th cleaning assembly, and an i-th recovery assembly, wherein i is a natural number and traverses from 1 to n, and n is a natural number and is not less than 2;

A cleaning device, having a cleaning mechanism capable of cleaning the polishing sheet to obtain a large-sized silicon carbide substrate;

Wherein, the large-size silicon carbide substrate is a silicon carbide substrate larger than 8 inches.

In a fourth aspect, the present invention also provides a low-stress processing method for silicon carbide substrates larger than 8 inches.

Beneficial Effects

Compared with the prior art, the beneficial effects of the silicon carbide exfoliation sheet and processing method based on laser cracking of the present invention include at least one of the following:

(1) The laser lift-off of the present invention can reduce the processing stress of silicon carbide wafers and reduce the amount of shape change after epitaxy (<10 μm).

(2) The method for processing silicon carbide exfoliation sheets based on laser cracking provided by the present invention can increase the number of sheets produced per unit length of silicon carbide rod (>30%).

(3) In the processing method provided by the present invention, crack extension is used instead of grinding, thereby achieving zero loss of crystal material.

(4) The 8-inch or larger silicon carbide peeling wafer of the present invention can provide a basis for formulating reasonable process parameters for subsequent thinning and polishing steps, thereby reducing processing damage to silicon carbide wafers.

Compared with the prior art, the system for preparing a silicon carbide substrate larger than 8 inches by laser lift-off of the present invention has the following beneficial effects:

(5) The laser lift-off technology used in the present invention can realize automated processing. Laser lift-off can reduce the processing stress of the wafer, reduce the amount of shape change after epitaxy, increase the number of wafers produced per unit rod length, and increase the number of silicon carbide crystals produced per unit thickness by 30%. In addition, the efficiency of the laser lift-off technology used in the present invention is increased by 2-3 times.

(6) The present invention adopts a thinning device, which can be designed according to the situation of the cutting piece, reduce the stress in the single-piece substrate, and greatly improve the thickness uniformity. In addition, the thinning device of the present invention can improve the flatness of the silicon carbide substrate and reduce the SFQR index of the silicon carbide substrate.

(7) The polishing device used in the present invention can significantly improve the thickness uniformity of the subsequent lining substrate while improving the surface roughness of the substrate, thereby achieving precise control of the wafer quality.

(8) The cleaning device used in the present invention can achieve single-wafer cleaning, making the substrate surface extremely hydrophilic, with good cleaning effect and low surface metal ion concentration.

(9) The laser lift-off system of the present invention for preparing silicon carbide substrates larger than 8 inches can solve the problems of large substrate stress, large SFQR value, large shape change before and after epitaxy, and surface metal contamination, and provide high-quality silicon carbide wafers.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings described herein are used to provide a further understanding of the present invention and constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

FIG1 is a schematic diagram showing a process flow diagram of an exemplary embodiment of a method for processing a silicon carbide exfoliation sheet by laser cracking according to the present invention;

FIG2 shows a structure diagram of a laser lift-off device in an exemplary embodiment of a system for preparing a silicon carbide substrate larger than 8 inches by laser lift-off according to the present invention;

FIG. 3 shows a structural diagram of a single-wafer polishing device in an exemplary embodiment of a system for preparing a silicon carbide substrate larger than 8 inches by laser lift-off according to the present invention.

The following are the descriptions of the reference numerals:

11-direction finder signal transmitter, 12-direction finder signal receiver;

211-first adjustment component, 2111-first adjustment knob, 212-second adjustment component, 2121-second adjustment knob;

31-laser head, 32-focusing lens;

41- Vacuum suction cup;

51 - first polishing mechanism, 511 - first polishing disc, 512 - first polishing head, 513 - first liquid supply assembly, 514 - first cleaning assembly, 52 - second polishing mechanism, 53 - third polishing mechanism.

Implementation

In order to more clearly illustrate the overall concept of the present invention, a detailed description is given below in an exemplary manner in conjunction with the accompanying drawings.

In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Therefore, the protection scope of the present invention is not limited to the specific embodiments disclosed below.

In addition, in the description of the present invention, it should be understood that the orientations or positional relationships indicated by terms such as "top", "bottom", "inside", "outside", "axial", "radial", and "circumferential" are based on the orientations or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, they should not be understood as limitations on the present invention.

In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection, or a communication; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

In the present invention, unless otherwise clearly specified and limited, the first feature "on" or "under" the second feature may be that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in an appropriate manner in any one or more embodiments or examples.

Example 1

FIG. 1 is a schematic diagram showing a process flow of an exemplary embodiment of a method for processing a silicon carbide exfoliation sheet based on laser cracking according to the present invention.

In an exemplary embodiment of the present invention, as shown in FIG1 , a method for processing a silicon carbide exfoliation sheet based on laser cracking includes the following steps:

S01. Detect the (0001) crystal plane of the silicon carbide ingot to obtain crystal plane position information.

Specifically, the principle of Bragg diffraction can be used for crystal plane detection, that is, the surface crystal of silicon carbide is composed of crystal plane families A, B, and C with a plane spacing of d. When the laser beam is projected onto the silicon carbide crystal at a grazing angle α, the scattering of the lattice on crystal plane A and the scattering of the lattice on crystal planes B and C interfere with each other. For the laser scattered rays of the same layer, when the angle between the scattered rays and the crystal plane is equal to the grazing angle, the rays produce constructive interference in this direction. For the scattered rays of the same layer, when the angle between the scattered rays and the crystal plane is equal to the grazing angle, the rays produce constructive interference in this direction. For the scattered rays of different layers, when the optical path difference is an integer multiple of the wavelength, the scattered rays of each surface reinforce each other to form a very large light intensity. Using this principle, crystal plane detection is completed and crystal plane information is obtained.

S02, calculating the angle between the crystal plane position information and the first plane, and determining whether the angle meets the requirement of a preset angle, wherein the first plane is always perpendicular to the first direction where the first laser beam is located.

Specifically, the first plane is the plane of the silicon carbide ingot that is substantially perpendicular to the first laser beam. The first direction is the direction of irradiation of the first laser beam. The angle value is the angle between the (0001) crystal plane of the silicon carbide ingot and the first plane of the silicon carbide ingot. The preset angle value may be a determined value selected within the range of 0 to 10°, and further, the preset angle value may be a determined value selected within the range of 0.5 to 3.5° or 4.5 to 7°. For example, it may also be 0° or 4°. The requirement for the preset angle value may be equal to the preset angle value, or it may be within 10% of the preset angle value, for example, 4±0.1°.

S03a. If the conditions are met, start the first laser beam to scan the silicon carbide ingot to form a surface to be peeled that contains multiple cracks and extends along the first plane.

Specifically, if the angle between the (0001) crystal plane of the silicon carbide ingot and the first plane of the silicon carbide ingot is within the preset angle value range, the first laser beam is started to perform laser scanning on the silicon carbide ingot to form a peeling surface containing multiple cracks and extending along the first plane. The average output power of the first laser beam can be 0.8~3.5W, the wavelength can be 780~1100nm, the scanning speed can be 300~700mm/s, the scanning spacing can be 0.1~0.5mm, the scanning time can be 10~40min, and the number of scans can be 2~6 times.

S03b. If not, adjust the angle of the silicon carbide ingot and/or the angle of the first direction, and return to step S02 until the angle value meets the requirement of the preset angle value, and then perform step S03a.

Specifically, if the angle between the (0001) crystal plane of the silicon carbide ingot and the first plane of the silicon carbide ingot is not within the preset angle value range, the angle of the silicon carbide ingot can be adjusted, that is, the (0001) plane of the silicon carbide ingot can be adjusted, or the first direction of the first laser beam can be adjusted. After the adjustment, return to step S02, calculate the angle value, and determine whether it meets the preset angle value. If it does, enter S03a; if it does not, continue to adjust the angle value until the preset angle value is met.

S04. Apply vibration to the surface to be peeled off to obtain a silicon carbide peeling sheet.

Vibration is applied to the surface to be peeled in step S03a so that the surface to be peeled extends or breaks along the cracks to obtain a peeling sheet. The vibration can be achieved by mechanical vibration, ultrasonic method, etc. For example, for the ultrasonic method, the frequency of the ultrasound can be 100-150KHZ, the ultrasonic time can be 10-60s, and the emission mode can be continuous wave or pulse wave.

The thickness of the silicon carbide peeling sheet of 8 inches or more obtained by the above processing method can be 100~1000μm, Bow≤60μm, Sori≤100μm, the damage layer depth ≤100μm and the maximum height of the surface crack step does not exceed 70% of the damage layer depth.

In the present invention, Bow refers to the curvature, which represents the degree of concavity or convexity of the center of the wafer relative to the reference plane. Sori refers to the warpage of the front surface based on the least squares method, which represents the degree of deviation of the substrate as a whole relative to the mid-plane. The shape change before and after epitaxy refers to the change of Bow before and after epitaxy, and the change of Sori before and after epitaxy.

Example 2

In another exemplary embodiment of the present invention, the method for processing a silicon carbide exfoliation sheet based on laser cracking may further include, in addition to the above steps: step S05 or step S05′.

Specifically, step S05 may be: grinding the stripping area on the silicon carbide ingot left in step S04 along the first plane, and performing steps S01 to S04 again to obtain another silicon carbide stripping sheet.

Step S05' may be: after grinding the peeling area left on the silicon carbide ingot in step S04 along the first plane, directly starting the first laser beam to scan the silicon carbide ingot again to form another peeling surface containing multiple cracks and extending along the first plane, and then performing step S04 to obtain another silicon carbide peeling sheet.

In step S03a, if the angle determination unit calculates and determines that the angle value meets the requirements of the preset angle value, the second laser beam can be started to scan the silicon carbide ingot in the circumferential direction of the silicon carbide ingot, and ensure that the second direction where the second laser beam is located is always in the first plane, that is, the second laser beam can completely irradiate the surface of the silicon carbide ingot for peeling in the circumferential direction. The cracking direction of the first laser beam is perpendicular to the laser incident direction, and the cracking direction of the second laser beam is along the laser incident direction. The laser cracking direction can be adjusted by spot shaping. It is conducive to the peeling of the edge circumference of the silicon carbide ingot, and can further optimize the depth of the damaged layer and the depth of the surface step crack. The second laser head is configured to be able to be controlled in conjunction with the first laser head. The two laser heads peel the silicon carbide ingot successively. The first laser head generates a first laser beam to peel the area of the silicon carbide ingot except the circumferential edge, and the second laser head generates a second laser beam to peel the circumferential edge area of the silicon carbide ingot. The focus of the first laser beam and the position of the second laser beam are controlled to ensure that the two generate cracks in the same plane. The second laser beam can optimize the depth of the damaged layer and the depth of the surface step crack by at least 10% compared with the result of peeling with only the first laser beam. The average output power of the second laser beam is 0.3 to 0.5 times the average output power parameter of the first laser beam, the wavelength is 780 to 1100 nm, the scanning speed is 0.3 to 0.5 times the scanning speed parameter of the first laser beam, the scanning spacing is 0.1 to 0.5 mm, the scanning time is 10 to 40 minutes, and the number of scans is 2 to 6 times.

The Bow of the silicon carbide peeling sheet larger than 8 inches obtained by the above processing method can be 30~57μm, Sori can be 50~97μm, the damage layer depth can be 60~95μm and the maximum surface crack step height can be 50~70% of the damage layer depth.

Example 3

In another exemplary embodiment of the present invention, a method for processing a silicon carbide exfoliation sheet based on laser cracking includes the following steps:

S01, detecting the (0001) crystal plane of the silicon carbide ingot to obtain crystal plane position information;

S02, setting a preset value to 0°±0.01°, calculating the angle between the crystal plane position information and the first plane, and determining whether the angle meets the requirement of the preset angle;

S03. Determine that the angle value is 0°, which meets the requirements of the preset angle value, start the first laser beam to scan the silicon carbide ingot, set the average output power of the first laser beam to 1.1w, the wavelength to 1064nm, the scanning speed to 300mm/s, the scanning spacing to 0.12mm, the scanning time to 20min, and the number of scans to 5 times. Start the second laser beam to scan around the circumference of the silicon carbide ingot, set the average output power of the second laser beam to 0.55w, the wavelength to 1064nm, the scanning speed to 150mm/s, the scanning spacing to 0.12mm, the scanning time to 20min, and the number of scans to 5 times. Form a surface to be peeled containing multiple cracks and extending along the first plane;

S04. Apply ultrasound to the surface to be peeled off in step S03. The frequency of the ultrasound is 150KHZ, the ultrasound time is 40s, and the emission mode is a pulse wave, to obtain an 8-inch silicon carbide peeling sheet 1#.

Example 4

In another exemplary embodiment of the present invention, a method for processing a silicon carbide exfoliation sheet based on laser cracking includes the following steps:

S01, detecting the (0001) crystal plane of the silicon carbide ingot to obtain crystal plane position information;

S02, setting a preset value to 4°±0.01°, calculating the angle between the crystal plane position information and the first plane, and determining whether the angle meets the requirement of the preset angle;

S03b, if the angle value is 0° and does not meet the preset value requirement, the angle of the silicon carbide ingot is adjusted by the inclination adjustment mechanism arranged below the silicon carbide ingot, and the process returns to step S02, and the adjustment and judgment are repeated multiple times until the angle value meets the preset angle value requirement, and then step S03a is performed. Here, the inclination adjustment mechanism can be arranged below a fixing unit (e.g., a negative pressure adsorption mechanism or a clamping mechanism) for fixing and supporting the lower end of the silicon carbide ingot, and can adjust the angle of the silicon carbide ingot along two directions (e.g., the X direction and the Y direction extending substantially along the horizontal plane direction) that are located in the same plane and perpendicular to each other, or in two parallel planes and perpendicular to each other.

S03a, judging that the angle value is 4°, which meets the requirement of the preset angle value, starting the first laser beam to scan the silicon carbide ingot, setting the average output power of the first laser beam laser to 2.5w, the wavelength to 1064nm, the scanning speed to 500mm/s, the scanning interval to 0.18mm, the scanning time to 30min, and the number of scans to 4 times. Forming a to-be-peeled surface containing multiple cracks and extending along the first plane;

S04. Apply ultrasound to the surface to be peeled off in step S03. The frequency of the ultrasound is 120KHZ, the ultrasound time is 30s, and the emission mode is a pulse wave, to obtain an 8-inch silicon carbide peeling sheet 2#.

Example 5

In another exemplary embodiment of the present invention, a method for processing a silicon carbide exfoliation sheet based on laser cracking includes the following steps:

S01, detecting the (0001) crystal plane of the silicon carbide ingot to obtain crystal plane position information;

S02, setting a preset value to 4°±0.01°, calculating the angle between the crystal plane position information and the first plane, and determining whether the angle meets the requirement of the preset angle;

S03b, if the angle value is 0° and does not meet the preset value requirement, the angle of the silicon carbide ingot is adjusted by the inclination adjustment mechanism arranged below the silicon carbide ingot, and the process returns to step S02, and the adjustment and judgment are repeated multiple times until the angle value meets the preset angle value requirement, and then step S03a is performed. Here, the inclination adjustment mechanism can be arranged below a fixing unit (e.g., a negative pressure adsorption mechanism or a clamping mechanism) for fixing and supporting the lower end of the silicon carbide ingot, and can adjust the angle of the silicon carbide ingot along two directions (e.g., the X direction and the Y direction extending substantially along the horizontal plane direction) that are located in the same plane and perpendicular to each other, or in two parallel planes and perpendicular to each other.

S03a. Determine that the angle value is 4°, which meets the requirement of the preset angle value, start the first laser beam to scan the silicon carbide ingot, set the average output power of the first laser beam to 2.5w, the wavelength to 1064nm, the scanning speed to 500mm/s, the scanning spacing to 0.18mm, the scanning time to 30min, and the number of scans to 4 times. Start the second laser beam to scan around the circumference of the silicon carbide ingot, set the average output power of the second laser beam to 1.0w, the wavelength to 1064nm, the scanning speed to 150mm/s, the scanning spacing to 0.18mm, the scanning time to 30min, and the number of scans to 4 times. Form a surface to be peeled containing multiple cracks and extending along the first plane;

S04. Apply ultrasound to the surface to be peeled off in step S03. The frequency of the ultrasound is 120KHZ, the ultrasound time is 30s, and the emission mode is a pulse wave, to obtain an 8-inch silicon carbide peeling sheet 3#.

Example 6

In another exemplary embodiment of the present invention, a method for processing a silicon carbide exfoliation sheet based on laser cracking includes the following steps:

S01, detecting the (0001) crystal plane of the silicon carbide ingot to obtain crystal plane position information;

S02, setting a preset value to 2°±0.01°, calculating the angle between the crystal plane position information and the first plane, and determining whether the angle meets the requirement of the preset angle;

S03b, if the angle value is 1°, which does not meet the preset value requirement, the angle of the first direction where the first laser beam is located is adjusted by the laser adjustment mechanism disposed above the first laser head, and the process returns to step S02, and the adjustment and judgment are repeated multiple times until the angle value meets the preset angle value requirement, and then step S03a is performed. Here, the laser adjustment mechanism can be changed in at least two dimensions to adjust the angle of the first direction, and can make the first laser beam always maintain the aforementioned adjusted angle during scanning.

S03a, judging that the angle value is 2°, which meets the requirement of the preset angle value, starting the first laser beam to scan the silicon carbide ingot, setting the average output power of the first laser beam laser to 3.2w, the wavelength to 1064nm, the scanning speed to 700mm/s, the scanning interval to 0.25mm, the scanning time to 10min, and the number of scans to 3 times. Forming a to-be-peeled surface containing multiple cracks and extending along the first plane;

S04. Apply ultrasound to the surface to be peeled in step S03. The frequency of the ultrasound is 100 KHZ, the ultrasound time is 20 seconds, and the emission mode is continuous wave, to obtain an 8-inch silicon carbide peeling sheet 4#.

Example 7

In another exemplary embodiment of the present invention, a method for processing a silicon carbide exfoliation sheet based on laser cracking includes the following steps:

S01, detecting the (0001) crystal plane of the silicon carbide ingot to obtain crystal plane position information;

S02, setting a preset value to 2°±0.01°, calculating the angle between the crystal plane position information and the first plane, and determining whether the angle meets the requirement of the preset angle;

S03b, if the angle value is 1°, which does not meet the preset value requirement, the angle of the first direction where the first laser beam is located is adjusted by the laser adjustment mechanism disposed above the first laser head, and the process returns to step S02, and the adjustment and judgment are repeated multiple times until the angle value meets the preset angle value requirement, and then step S03a is performed. Here, the laser adjustment mechanism can be changed in at least two dimensions to adjust the angle of the first direction, and can make the first laser beam always maintain the aforementioned adjusted angle during scanning.

S03a. Determine that the angle value is 2°, which meets the requirement of the preset angle value, start the first laser beam to scan the silicon carbide ingot, set the average output power of the first laser beam to 3.2w, the wavelength to 1064nm, the scanning speed to 700mm/s, the scanning spacing to 0.25mm, the scanning time to 10min, and the number of scans to 3 times. Start the second laser beam to scan around the circumference of the silicon carbide ingot, set the average output power of the second laser beam to 1.5w, the wavelength to 1064nm, the scanning speed to 350mm/s, the scanning spacing to 0.25mm, the scanning time to 10min, and the number of scans to 3 times. Form a surface to be peeled containing multiple cracks and extending along the first plane;

S04. Apply ultrasound to the surface to be peeled in step S03. The frequency of the ultrasound is 100 KHZ, the ultrasound time is 20 seconds, and the emission mode is continuous wave, to obtain an 8-inch silicon carbide peeling sheet 5#.

Example 8

In another exemplary embodiment of the present invention, a method for processing a silicon carbide exfoliation sheet based on laser cracking includes the following steps:

S01, detecting the (0001) crystal plane of the silicon carbide ingot to obtain crystal plane position information;

S02, setting a preset value to 6°±0.01°, calculating the angle between the crystal plane position information and the first plane, and determining whether the angle meets the requirement of the preset angle;

S03. Determine that the angle value is 6°, which meets the requirement of the preset angle value, start the first laser beam to scan the silicon carbide ingot, set the average output power of the first laser beam to 0.8w, the wavelength to 1064nm, the scanning speed to 600mm/s, the scanning spacing to 0.5mm, the scanning time to 40min, and the number of scans to 6 times. Start the second laser beam to scan around the circumference of the silicon carbide ingot, set the average output power of the second laser beam to 0.32w, the wavelength to 1064nm, the scanning speed to 240mm/s, the scanning spacing to 0.5mm, the scanning time to 40min, and the number of scans to 6 times. Form a surface to be peeled containing multiple cracks and extending along the first plane;

S04. Apply ultrasound to the surface to be peeled in step S03. The frequency of the ultrasound is 200 KHZ, the ultrasound time is 10 seconds, and the emission mode is continuous wave, to obtain an 8-inch silicon carbide peeling sheet 6#.

The 8-inch silicon carbide exfoliation sheets 1# to 6# obtained in Examples 3 to 8 above were subjected to performance tests, and the test results are shown in Table 1.

Table 1 Silicon carbide peeling sheet performance test table

Peel-off sheet	Thickness (μm)	size (")	Bow (μm)	Sori (μm)	Depth of damaged layer (μm)	Surface crack step height (μm)
1#	389	8	42.394	82.943	80.2	48.125
2#	286	8	40.432	75.829	78.85	55.115
3#	155	8	35.637	55.163	68.7	34.35
4#	556	8	56.203	96.656	94.892	66.424
5#	336	8	47.89	73.257	75.459	45.275
6#	974	8	59.538	97.309	98.95	69.265

As shown in Table 1, the silicon carbide peeling sheets 1#~6# obtained by the processing method of the present application have a thickness of 100~1000μm, a size of 8 inches, Bow≤60μm, Sori≤100μm, a damage layer depth≤100μm, and a maximum surface crack step height of no more than 70% of the damage layer depth. Furthermore, the silicon carbide peeling sheets 1#~6# have a Bow of 30~57μm, a Sori of 50~97μm, a damage layer depth of 60~95μm, and a maximum surface crack step height of 50~70% of the damage layer depth. Therefore, the processing method of the present application can reduce the processing damage of silicon carbide wafers, improve the processing efficiency, and provide a basis for formulating reasonable process parameters for subsequent thinning and polishing processes.

In an exemplary embodiment of the present invention, a system for preparing a silicon carbide substrate larger than 8 inches by laser lift-off of the present invention comprises: a laser lift-off device, a thinning device, a polishing device, and a cleaning device.

The laser lift-off device is composed of a crystal plane detection unit, an angle determination unit, an angle adjustment unit, a laser scanning unit, an external force applying unit, and a fixing unit.

The crystal plane detection unit is arranged above the position of the silicon carbide ingot to be peeled off, and can detect the (0001) crystal plane of the silicon carbide ingot to obtain the crystal plane position information. Specifically, the crystal plane detection unit includes an orientation component, such as an orientation instrument, which can detect the crystal plane information using the Bragg diffraction principle, and then transmit the detected information to the angle determination unit.

The angle determination unit is configured to receive crystal plane position information, calculate the angle value between the crystal plane position information and the first plane, determine whether the angle value meets the requirements of the preset angle value, and if so, output a first signal, and if not, output a second signal, wherein the first plane is always perpendicular to the first direction where the first laser beam is located. Specifically, the first plane is the surface where the silicon carbide ingot is located that is perpendicular to the first laser beam. The first direction is the direction of irradiation of the first laser beam. The angle value is the angle between the (0001) crystal plane of the silicon carbide ingot and the first plane of the silicon carbide ingot, and the preset angle value is a determined value selected in the range of 0 to 10, and further, the preset angle value is a determined value selected in the range of 0.5 to 3.5 or 4.5 to 7. The first signal and the second signal are electrical signals or wireless signals, but the present invention is not limited thereto.

After judgment, if the angle value between the (0001) plane of the silicon carbide ingot and the first plane meets the preset angle value, a first signal is output to the laser scanning unit; if the angle value between the (0001) plane of the silicon carbide ingot and the first plane does not meet the preset angle value, a second signal is output to the angle adjustment unit.

The angle adjustment unit includes an ingot angle adjustment mechanism and/or a first laser beam angle adjustment mechanism. Specifically, the ingot angle adjustment mechanism is capable of adjusting the angle of the silicon carbide ingot, and includes a first adjustment component and a second adjustment component arranged below the fixing unit, wherein the first adjustment component is configured to be capable of adjusting the silicon carbide ingot along the X-axis direction, and the second adjustment component is configured to be capable of adjusting the silicon carbide ingot along the Y-axis direction, wherein the X-axis direction and the Y-axis direction are located in the same plane and are perpendicular to each other or are parallel to two planes and are skewed and perpendicular. The first laser beam angle adjustment mechanism is configured to be capable of adjusting the first direction in which the first laser beam is located.

The angle adjustment unit is configured to receive a second signal transmitted by the angle determination unit, and activate the ingot angle adjustment mechanism to adjust the angle of the silicon carbide ingot according to the received second signal, and/or activate the first laser beam angle adjustment mechanism to adjust the first direction. After adjusting the angle of the silicon carbide ingot and/or the angle of the first direction, the information is transmitted to the angle determination unit again, and the angle value between the crystal plane position information and the first plane is recalculated to determine whether the angle value meets the requirements of the preset angle value.

The laser scanning unit includes a first laser head capable of generating a first laser beam, and is configured to receive a first signal and start the first laser head to scan the silicon carbide ingot to form a surface to be peeled containing multiple cracks and extending along the first plane. The average output power of the first laser beam is 0.8-3.5W, the wavelength is 780-1100nm, the scanning speed is 300-700mm/s, the scanning spacing is 0.5-1mm, the scanning time is 10-40min, and the number of scans is 2-6 times.

Specifically, the first laser head is divided into a scanning state and a non-scanning state. For example, when the first laser head is in a scanning state, the distance between the first laser head and the silicon carbide crystal ingot is 0.5~2cm. When the first laser head is in a non-scanning state, the distance between the first laser head and the silicon carbide crystal ingot is 10~20cm.

The laser scanning unit also includes a focusing lens for forming a focusing spot of uniform size with the first laser beam in the entire first plane, which is conducive to uniformly irradiating the first laser beam onto the surface or inside of the silicon carbide ingot.

After the laser scanning unit receives the first signal transmitted by the angle determination unit, the first laser head changes from a non-scanning state to a scanning state, sets the focal position according to the thickness of the peeled wafer, and generates a first laser beam to perform a serpentine scan or a circular scan on the silicon carbide ingot along the first plane to generate a crack that is parallel or substantially parallel to the first plane of the silicon carbide ingot.

In another embodiment of the present invention, the laser scanning unit also includes a second laser head capable of generating a second laser beam. If the angle determination unit calculates and determines that the angle value meets the requirement of the preset angle value, the second laser beam can be started to scan the silicon carbide ingot in the circumferential direction of the silicon carbide ingot, and ensure that the second direction of the second laser beam is always in the first plane, that is, the second laser beam can completely irradiate the surface of the silicon carbide ingot for circumferential peeling. The fracturing direction of the first laser beam is perpendicular to the laser incident direction, and the fracturing direction of the second laser beam is along the laser incident direction, and the laser fracturing direction can be adjusted by spot shaping. It is beneficial to the peeling of the edge circumference of the silicon carbide ingot, and can further optimize the depth of the damaged layer and the depth of the surface step cracks. The second laser head is configured to be able to be controlled in linkage with the first laser head. The two laser heads successively peel off the silicon carbide ingot. The first laser head generates a first laser beam to peel off the area other than the circumferential edge of the silicon carbide ingot. The second laser head generates a second laser beam to peel off the circumferential edge area of the silicon carbide ingot. The focus of the first laser beam and the position of the second laser beam are controlled to ensure that the two generate cracks in the same plane. Compared with the result of peeling with only the first laser beam, the second laser beam can optimize the depth of the damaged layer and the depth of the surface step crack by at least 10%. The average output power of the second laser beam is 0.3~0.5 times the average output power parameter of the set first laser beam, the wavelength is 780~1100nm, the scanning speed is 0.3~0.5 times the scanning speed parameter of the set first laser beam, the scanning spacing is 0.1~0.5mm, the scanning time is 10~40min, and the number of scans is 2~6 times.

The angle adjustment unit also includes a second laser beam angle adjustment mechanism capable of adjusting the second direction where the second laser beam is located, and is configured to receive a second signal and activate the second laser beam angle adjustment mechanism so that the second direction is always within the first plane. The angle adjustment unit receives the second signal transmitted by the angle determination unit, and activates the ingot angle adjustment mechanism to adjust the angle of the silicon carbide ingot according to the received second signal, and/or activates the first laser beam angle adjustment mechanism to adjust the first direction, and simultaneously activates the second laser beam angle adjustment mechanism to adjust the second direction. After adjusting the angle of the silicon carbide ingot and/or the angle of the first direction, and adjusting the angle of the second direction, the information is transmitted to the angle determination unit again, and the angle value between the crystal plane position information and the first plane is recalculated to determine whether the angle value meets the requirements of the preset angle value.

In another embodiment of the present invention, the laser stripping device may further include a grinding unit. One operation mode of the device of this embodiment may be: the grinding unit grinds the stripping area left on the silicon carbide ingot along the first plane, uses the crystal plane detection unit to detect the crystal plane information, uses the angle determination unit to recalculate the angle value between the crystal plane position information and the first plane, and judges whether the angle value meets the requirements of the preset angle value. If it meets the requirements, the first laser head is started to generate the first laser beam to scan the silicon carbide ingot again to form another surface to be stripped containing multiple cracks and extending along the first plane, and then the external force application unit is used to apply vibration to the surface to be stripped to obtain another silicon carbide stripping sheet. If it does not meet the requirements, the angle of the silicon carbide ingot and/or the angle of the first direction are adjusted by the angle adjustment unit, and then the information is transmitted to the angle determination unit again, and the angle value between the crystal plane position information and the first plane is recalculated to judge whether the angle value meets the requirements of the preset angle value.

Another operation mode of the device of this embodiment may also be: after grinding the peeling area remaining on the silicon carbide ingot along the first plane, directly start the first laser head to generate the first laser beam to scan the silicon carbide ingot again to form another peeling surface containing multiple cracks and extending along the first plane, and then use the external force applying unit to apply vibration to the peeling surface to obtain another silicon carbide peeling sheet. Providing the grinding unit can improve the peeling quality of the silicon carbide peeling sheet and improve the processing efficiency.

The external force applying unit is configured to apply vibration to the surface to be peeled to obtain a silicon carbide peeling sheet. Specifically, the external force applying unit is an ultrasonic component capable of emitting ultrasound toward the surface to be peeled, and further, the ultrasonic frequency of the ultrasonic component is 100-150KHZ, and the ultrasonic time is 10-60s.

The fixing unit is configured to fix and support the silicon carbide ingot, including a holding mechanism for fixing the silicon carbide ingot. For example, the clamping mechanism may be a vacuum suction cup, which uses vacuum negative pressure to absorb the silicon carbide ingot to achieve the purpose of clamping the workpiece. The vacuum suction cup may be made of stainless steel, ceramic, or nitrile rubber, but the present invention is not limited thereto.

The size of the silicon carbide peeling sheet obtained by the laser peeling device is 8 inches, the surface roughness is 10~50μm, the GBIR is <20μm, Bow≤60μm, Sori≤100μm, the damage layer depth is ≤100μm and the maximum height of the surface crack step does not exceed 70% of the damage layer depth, and the surface is evenly covered with microcracks in the laser scanning direction. In addition, the thickness of the silicon carbide peeling sheet is 100~1000μm.

The method for preparing a silicon carbide peeling sheet using the laser peeling device of the present invention specifically comprises the following steps:

S01, using a crystal plane detection unit to detect the (0001) crystal plane of the silicon carbide ingot to obtain crystal plane position information;

S02, using an angle determination unit to calculate an angle value between the crystal plane position information and the first plane, and determining whether the angle value meets a preset angle value requirement, wherein the first plane is always perpendicular to a first direction where the first laser beam is located;

S03a, if satisfied, start the first laser head of the laser scanning unit to generate a first laser beam to scan the silicon carbide ingot to form a to-be-peeled surface containing multiple cracks and extending along the first plane;

S03b, if not satisfied, adjusting the angle of the silicon carbide ingot and/or the angle of the first direction by using the angle adjustment unit, and returning to step S02, and again calculating the angle value between the crystal plane position information and the first plane by using the angle determination unit, until the angle value meets the requirement of the preset angle value;

S04, applying vibration to the surface to be peeled off by using an external force applying unit to obtain a silicon carbide peeling sheet.

Another method for preparing silicon carbide stripping using the laser stripping device of the present invention specifically comprises the following steps:

S01, using a crystal plane detection unit to detect the (0001) crystal plane of the silicon carbide ingot to obtain crystal plane position information;

S02, using an angle determination unit to calculate an angle value between the crystal plane position information and the first plane, and determining whether the angle value meets a preset angle value requirement, wherein the first plane is always perpendicular to a first direction where the first laser beam is located;

S03a, if satisfied, start the first laser head of the laser scanning unit to generate a first laser beam to scan the silicon carbide ingot to form a to-be-peeled surface containing multiple cracks and extending along the first plane;

S03b, if not satisfied, adjusting the angle of the silicon carbide ingot and/or the angle of the first direction by using the angle adjustment unit, and returning to step S02, and again calculating the angle value between the crystal plane position information and the first plane by using the angle determination unit, until the angle value meets the requirement of the preset angle value;

S04, applying vibration to the surface to be peeled off by using an external force applying unit to obtain a silicon carbide peeling sheet;

S05, grinding the stripping area on the silicon carbide ingot left in step S04 along the first plane using a grinding unit, and performing steps S01 to S04 again to obtain another silicon carbide stripping sheet.

Alternatively, after the peeling area left on the silicon carbide ingot in step S04 is polished along the first plane by a polishing unit, the first laser beam is directly started to scan the silicon carbide ingot again to form another peeling surface containing multiple cracks and extending along the first plane, and then step S04 is performed to obtain another silicon carbide peeling sheet.

The thinning device has a grinding mechanism capable of thinning at least a portion of one side of the single release sheet and/or thinning at least a portion of the other side of the single release sheet.

The grinding component includes a rough grinding wheel and a fine grinding wheel. The grinding wheel inclination angle set during the rough grinding process is 0°~0.5°, the feed speed is 5~30μm/min, the grinding wheel speed is 1000~4000rpm, and the grinding wheel mesh number is 2000~5000 mesh; preferably, the rough grinding wheel is set with a grinding wheel inclination angle of 0.1°~0.3°, a feed speed of 10~20μm/min, a grinding wheel speed of 2000~250rpm, and a grinding wheel mesh number of 3000 ~4000 mesh; the grinding wheel inclination angle of the fine grinding wheel is -0.5°~0°, the feed speed is 3~20μm/min, the grinding wheel speed is 1000~3000rpm, and the grinding wheel mesh number is 15000~40000 mesh; preferably, the grinding wheel inclination angle of the fine grinding wheel is -0.3°~-0.1°, the feed speed is 5~15μm/min, the grinding wheel speed is 1500~2500rpm, and the grinding wheel mesh number is 20000~30000 mesh.

The size of the silicon carbide thinned sheet obtained by the thinning device is 8 inches, SFQR≤1.2μm, GBIR≤5μm, Bow≤10μm, Sori≤15μm, and surface roughness≤10nm.

The polishing device includes a workbench and an i-th polishing mechanism connected in series through the workbench, wherein the i-th polishing mechanism includes an i-th polishing assembly, an i-th liquid supply assembly, an i-th cleaning assembly, and an i-th recovery assembly, wherein i is a natural number and traverses from 1 to n, and n is a natural number and is not less than 2. For example, when i is 2, it includes a first polishing mechanism and a second polishing mechanism connected in series. The first polishing mechanism includes a first polishing assembly, a first liquid supply assembly, a first cleaning assembly, and a first recovery assembly; the second polishing mechanism includes a second polishing assembly, a second liquid supply assembly, a second cleaning assembly, and a second recovery assembly. However, the present invention is not limited thereto, and multiple polishings can be performed according to the quality of the required wafer.

The i-th polishing assembly is fixed on the workbench and includes an i-th polishing disc that can rotate and is provided with an i-th polishing pad, and an i-th polishing head; the i-th polishing head is located at the periphery of the i-th polishing disc, and the distance between the axis of the i-th polishing head and the axis of the i-th polishing disc is in the range of 100-200 mm. During the polishing process, the i-th polishing head can fix the wafer to be polished to realize the polishing operation of pressing one surface of the wafer to be polished on the i-th polishing disc. For example, a cylinder structure is provided on the upper part of the i-th polishing head; during the polishing process, the wafer to be polished can be adsorbed onto the i-th polishing head to fix the wafer to be polished, and at the same time, the cylinder structure can apply downward pressure to the polishing head to realize single-sided polishing of the wafer to be polished. In addition, the i-th polishing pad can be mounted on the polishing disc or vacuum adsorbed on the polishing disc, and the roughness of the i-th polishing pad is higher than that of the i+1-th polishing pad, which helps to further reduce the surface roughness of the wafer. In addition, during the polishing process, the i-th polishing disc can rotate along the axis, and the i-th polishing head can also rotate along the axis. The rotation of the two aspects can make the wafer to be polished in relative rotational friction during single-sided polishing, which can better ensure the roughness and uniformity of the wafer thickness. During the polishing process, the i-th polishing disc and the i-th polishing head can rotate clockwise or counterclockwise at the same time, and the rotation speed of the i-th polishing disc is higher than that of the i-th polishing head.

The i-th liquid supply assembly is used to inject polishing liquid into the i-th polishing disc. For example, the i-th liquid supply assembly is fixed above the i-th polishing disc and includes an i-th polishing liquid barrel, which is connected to a flow rate control pipe to achieve dripping of the polishing liquid into the polishing disc at a certain flow rate. Alternatively, the i-th liquid supply assembly can directly drip the polishing liquid into the polishing disc through a straw. However, the present invention is not limited thereto.

The i-th cleaning component is located on both sides of the polishing disc and can clean the waste residue during the polishing process. There is always friction during the polishing process. If the friction track is not very uniform, part of the fluff on the polishing pad will be worn more. The cleaning component can be used to scrape the fluff off the polishing disc to ensure a certain degree of removal rate. For example, the cleaning component can be a brush component that can swing at a certain angle during the polishing process to remove the residue on the surface of the polishing disc. For example, a 180° angle swing.

The i-th recovery component is located below the polishing disc, and can recover the waste liquid and waste residue after polishing; and the surface roughness of the wafer obtained by the i+1-th polishing mechanism is less than the surface roughness of the wafer obtained by the i-th polishing mechanism. For example, the i-th recovery component includes the i-th recovery tank. A channel connected to the i-th recovery component is provided below and at the edge of the i-th polishing disc for collecting the waste liquid and waste residue after polishing into the recovery tank. The waste liquid can be further used for wafer polishing after filtering, but in order to further ensure the quality of the wafer, the waste liquid can generally continue to be used as polishing liquid and be reused 1-2 times.

The surface roughness of the polished sheet obtained after polishing by the tandem polishing device is not higher than 0.5nm, GBIR is <3μm, Bow is <20μm, Sori is <40μm, and there is no trace, crack or damage on the surface.

In another embodiment of the present invention, the serial polishing device further comprises an automatic moving component, which is similar to a manipulator component and can move the wafer to be polished to the i-th polishing mechanism, move the wafer from the i-th polishing mechanism to the i+1-th polishing mechanism, or move the wafer from the i+1 polishing mechanism into the wafer storage component after polishing. In addition, the automatic moving component can move in a straight line or at a certain angle. For example, when the wafer to be polished is polished three times in series, the automatic moving component can move the wafer to be polished to the first polishing component, and when the first polishing is completed, the automatic moving component can move the wafer after the first polishing from the first polishing component to the second polishing component, and after the second polishing is completed, the automatic moving component can move the wafer after the second polishing from the second polishing component to the third polishing component, and after the third polishing is completed, the automatic moving component can move the wafer after the third polishing to the wafer storage component or perform polishing on the other side of the wafer. The first polishing mechanism is a rough polishing mechanism for rough polishing the wafer, the second polishing mechanism is a medium polishing mechanism for medium polishing the wafer, and the third polishing mechanism is a fine polishing mechanism for fine polishing the wafer. The roughness of the wafer obtained by rough polishing is higher than that of medium polishing, and the roughness of the wafer obtained by medium polishing is higher than that of fine polishing.

The cleaning device has a cleaning mechanism capable of cleaning the polishing sheet to obtain a large-sized silicon carbide substrate, and a clamping mechanism for fixing a single wafer. The clamping mechanism can be a vacuum suction cup, which uses vacuum negative pressure to adsorb the silicon carbide wafer to achieve the purpose of clamping the workpiece. The vacuum suction cup can be made of stainless steel, ceramic, or nitrile rubber, but the present invention is not limited thereto.

In the present invention, SFQR (Site flatness front least-squares range) refers to local flatness, representing the maximum thickness difference per unit square area. Bow refers to curvature, representing the degree of concavity or convexity of the center of the wafer relative to the reference plane. Sori refers to the warpage of the front surface based on the least squares method, representing the degree of deviation of the substrate as a whole relative to the mid-plane. GBIR (Global flatness back ideal range) refers to the total thickness deviation, representing the difference between the maximum and minimum values of each measuring point within the reference plane and the measurement range. The shape change before and after epitaxy refers to the change of Bow before and after epitaxy and the change of Sori before and after epitaxy.

Example 9

FIG. 2 shows a structure diagram of a laser lift-off device in an exemplary embodiment of a system for laser lift-off to prepare silicon carbide substrates larger than 8 inches in the present application.

In this embodiment, as shown in FIG2 , the device for preparing silicon carbide peeling sheets by laser cracking is composed of a crystal plane detection unit, an angle determination unit (not shown), an angle adjustment unit, a laser scanning unit, an external force applying unit (not shown), and a fixing unit.

The crystal plane detection unit is arranged above the position of the silicon carbide ingot to be stripped, and includes an orientator signal transmitter 11 and an orientator signal receiver 12. It uses the Bragg diffraction principle to detect the (0001) crystal plane of the silicon carbide ingot to obtain the crystal plane position information, and then transmits the detected crystal plane information to the angle determination unit.

The angle determination unit is configured to receive crystal plane position information, calculate the angle value between the crystal plane position information and the first plane, and determine whether the angle value meets the requirements of the preset angle value. If so, a first signal is output, and if not, a second signal is output, wherein the first plane is always perpendicular to the first direction where the first laser beam is located. The preset angle value is a determined value selected within the range of 0 to 10, and further, the preset angle value is a determined value selected within the range of 0.5 to 3.5 or 4.5 to 7. The first signal and the second signal are electrical signals. After judgment, if the angle value between the (0001) plane of the silicon carbide ingot and the first plane meets the preset angle value, the first signal is output to the laser scanning unit, and if the angle value between the (0001) plane of the silicon carbide ingot and the first plane does not meet the preset angle value, the second signal is output to the angle adjustment unit.

The angle adjustment unit includes an ingot angle adjustment mechanism and/or a first laser beam angle adjustment mechanism (not shown). The ingot angle adjustment mechanism is capable of adjusting the angle of the silicon carbide ingot, and includes a first adjustment component 211 and a second adjustment component 212 disposed below the fixing unit. The first adjustment component 211 includes a first adjustment knob 2111, and the first adjustment knob 2111 is rotated clockwise or counterclockwise to adjust the movement of the silicon carbide ingot along the X-axis direction. The second adjustment component 212 includes a second adjustment knob 2121, and the second adjustment knob 2121 is rotated clockwise or counterclockwise to adjust the movement of the silicon carbide ingot along the Y-axis direction. The X-axis direction and the Y-axis direction are located in the same plane and are perpendicular to each other. The first laser beam angle adjustment mechanism is configured to be capable of adjusting the first direction in which the first laser beam is located.

The angle adjustment unit is configured to receive a second signal transmitted by the angle determination unit, and activate the ingot angle adjustment mechanism to adjust the angle of the silicon carbide ingot according to the received second signal, and/or activate the first laser beam angle adjustment mechanism to adjust the first direction. After adjusting the angle of the silicon carbide ingot and/or the angle of the first direction, the information is transmitted to the angle determination unit again, and the angle value between the crystal plane position information and the first plane is recalculated to determine whether the angle value meets the requirements of the preset angle value.

The laser scanning unit includes a first laser head 31 capable of generating a first laser beam and a focusing lens 32. The laser scanning unit is configured to receive a first signal and start the first laser head 31 to scan the silicon carbide ingot to form a surface to be peeled containing multiple cracks and extending along the first plane. The first laser beam generated by the first laser head 31 has an average output power of 0.8-3.5 W, a wavelength of 780-1100 nm, a scanning speed of 300-700 mm/s, a scanning pitch of 0.5-1 mm, a scanning time of 10-40 min, and a scanning number of 2-6 times.

The first laser head 31 is divided into a scanning state and a non-scanning state. When the first laser head 31 is in the scanning state, the distance between the first laser head 31 and the silicon carbide ingot is 0.5-2 cm. When the first laser head 31 is in the non-scanning state, the distance between the first laser head 31 and the silicon carbide ingot is 10-20 cm. After the laser scanning unit receives the first signal transmitted by the angle determination unit, the first laser head 31 changes from the non-scanning state to the scanning state, sets the focus position according to the thickness of the peeled wafer, generates a first laser beam to perform serpentine scanning on the silicon carbide ingot along the first plane, so as to generate a crack parallel or substantially parallel to the (0001) crystal plane of the silicon carbide ingot.

The focusing lens 32 is used to form a focusing spot of uniform size of the first laser beam in the entire first plane, which is conducive to uniform irradiation of the first laser beam onto the surface or the inside of the silicon carbide ingot.

The external force applying unit is an ultrasonic component capable of emitting ultrasound toward the surface to be peeled, applying ultrasonic vibration to the surface to be peeled, and obtaining a silicon carbide peeling sheet. The ultrasonic frequency of the ultrasonic component is 100-150KHZ, and the ultrasonic time is 10-60s.

The fixing unit is configured to fix and support the silicon carbide ingot, and includes a vacuum chuck 41 for fixing the silicon carbide ingot, and uses vacuum negative pressure to absorb the silicon carbide ingot to achieve the purpose of clamping the workpiece. The vacuum chuck 41 can be made of ceramic material.

Example 10

FIG. 3 shows a structural diagram of a laser polishing device in an exemplary embodiment of a system for preparing silicon carbide substrates larger than 8 inches by laser lift-off according to the present application.

In this embodiment, as shown in FIG3 , the polishing device includes: a workbench and a first polishing mechanism 51, a second polishing mechanism 51 and a third polishing mechanism 51 connected in series in sequence through the workbench. During the polishing process, the thinned sheet is placed in the wafer carrying assembly to be polished. During polishing, the automatic moving assembly moves the thinned sheet to be polished to the first polishing mechanism 51, firstly polishes the first time through the first polishing mechanism 51, then polishes the wafer after the first polishing for the second time in the second polishing mechanism 52, and finally polishes the wafer after the second polishing for the third time in the third polishing mechanism 53 to obtain the desired polished sheet, and moves the obtained polished sheet to the wafer storage assembly after polishing through the automatic moving assembly. Among them, the automatic moving assembly can be set to one or more, and the automatic moving assembly can move at a straight angle or at a certain angle. For example, three polishing mechanisms can be arranged in sequence to form a circle, an automatic moving assembly can be set to move at an angle of 360°, or an automatic moving assembly can be set to move at a certain angle in each step. However, the present invention is not limited to this. The automatic moving assembly is respectively set at the beginning and end of polishing. In addition, the present invention can also realize the switching of the wafer workpiece to be polished by manually taking out the workpiece.

As shown in FIG3 , the polishing assembly is fixed on a workbench and includes a first polishing disc 511 and a first polishing head 512 that can rotate and is provided with a polishing pad (not shown in the figure); the first polishing head 512 is located at the edge of the first polishing disc 511, and during the polishing process, the first polishing head 512 can fix the wafer to be polished to achieve a polishing operation by pressing one surface of the wafer to be polished on the first polishing disc 511. For example, a cylinder structure is provided on the upper part of the first polishing head 512; during the polishing process, the wafer to be polished can be adsorbed under the first polishing head 512 to fix the wafer to be polished, and at the same time, the cylinder structure can apply downward pressure to the first polishing head 511 to achieve single-sided polishing of the wafer to be polished. In addition, the polishing pad can be bonded to the first polishing disc 511, and the roughness of the second polishing pad is lower than that of the first polishing pad, which helps to further reduce the surface roughness of the wafer. In addition, during the polishing process, the first polishing disc 511 can rotate along the axis, and the second polishing head 512 can also rotate along the axis. The rotation of the first polishing disc 511 and the first polishing head 512 can put the wafer to be polished in a relative rotational friction state, so that the roughness of the polished wafer is guaranteed while ensuring the uniformity of the wafer thickness. In addition, during the polishing process, the first polishing disc 511 and the first polishing head 512 can rotate clockwise or counterclockwise at the same time, and the rotation speed of the first polishing disc 511 is higher than that of the first polishing head 512.

The first liquid supply assembly 513 is fixed above the first polishing plate 511 and includes a polishing liquid barrel (not shown in the figure), and the polishing liquid barrel is connected to the flow rate control pipeline to achieve the polishing liquid dripping into the polishing plate at a certain flow rate. Alternatively, the first liquid supply assembly 513 can directly drip the polishing liquid into the first polishing plate 511 through a straw. However, the present invention is not limited to this.

The first cleaning component 513 is located at the edge of the first polishing disc 511 and can clean the waste residue on the polishing disc during the polishing process. Since there is friction during the polishing process, if the friction track is not very uniform, part of the fluff on the polishing pad will be worn more. The fluff can be scraped upright from the polishing pad by the cleaning component to ensure a certain degree of removal rate. For example, the cleaning component in this embodiment can be a brush component, which can swing at a certain angle during the polishing process to remove the residue on the surface of the polishing disc. For example, it can swing at an angle of 180°.

The recovery component (not shown in the figure) is located below the first polishing disc 511, and can recover the waste liquid and waste residue after polishing. For example, in this embodiment, the recovery component includes a recovery tank. A channel connected to the recovery component is provided below and at the edge of the first polishing disc 511 for collecting the waste liquid and waste residue after polishing into the recovery tank. The waste liquid can be further used for wafer polishing after filtering.

This invention is funded by the special fund of Taishan Industry Leading Talent Project.

The above description is only an embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent substitution, improvement, etc. made within the spirit and principle of the present invention should be included in the scope of the claims of the present invention.

Claims (20)

1. A method for processing a silicon carbide peeling sheet based on laser cracking, characterized in that the processing method comprises the steps of:

   S01, detecting the (0001) crystal plane of the silicon carbide ingot to obtain crystal plane position information;

   S02, calculating the angle between the crystal plane position information and the first plane, and determining whether the angle meets the requirement of a preset angle, wherein the first plane is always perpendicular to the first direction where the first laser beam is located;

   S03a, if satisfied, start the first laser beam to scan the silicon carbide ingot to form a to-be-peeled surface containing multiple cracks and extending along the first plane; S03b, if not satisfied, adjust the angle of the silicon carbide ingot and/or the angle of the first direction, and return to step S02 until the angle value meets the requirement of the preset angle value;

   S04, applying vibration to the surface to be peeled off to obtain a silicon carbide peeling sheet.
2. The method for processing silicon carbide peeling sheets based on laser cracking according to claim 1 is characterized in that the preset angle value is a determined value selected within the range of 0~10, and further, the angle value is a determined value selected within the range of 0.5~3.5 or 4.5~7.
3. According to the laser cracking-based silicon carbide peeling sheet processing method of claim 1, it is characterized in that the processing method further includes: S05, grinding the peeling area left on the silicon carbide ingot in step S04 along the first plane, and performing steps S01 to S04 again to obtain another silicon carbide peeling sheet; or after grinding the peeling area left on the silicon carbide ingot in step S04 along the first plane, directly starting the first laser beam to scan the silicon carbide ingot again to form another surface to be peeled containing multiple cracks and extending along the first plane, and then performing step S04 to obtain another silicon carbide peeling sheet.
4. The method for processing silicon carbide peeling sheets based on laser cracking according to claim 1 is characterized in that step S03 also includes: when the angle value meets the requirement of a preset angle value, starting a second laser beam to scan the silicon carbide ingot in a circumferential direction thereof, and ensuring that the second direction of the second laser beam is always within the first plane.
5. The silicon carbide peeling sheet processing method based on laser cracking according to claim 1 or 2 is characterized in that the average output power of the first laser beam is 0.8~3.5W, the wavelength is 780~1100nm, the scanning speed is 300~700mm/s, the scanning interval is 0.1~0.5mm, the scanning time is 10~40min, and the number of scans is 2~6 times.
6. According to the laser cracking-based silicon carbide peeling sheet processing method of claim 5, it is characterized in that the thickness of the silicon carbide peeling sheet is 100~1000μm.
7. According to the laser cracking-based silicon carbide peeling sheet processing method of claim 1, it is characterized in that the vibration is achieved by ultrasound, and further, the frequency of the ultrasound is 100~150KHZ, the ultrasound time is 10~60s, and the emission mode is continuous wave or pulse wave.
8. A silicon carbide peeling sheet larger than 8 inches, characterized in that Bow≤60μm, Sori≤100μm, damage layer depth≤100μm and the maximum surface crack step height does not exceed 70% of the damage layer depth.
9. The silicon carbide peeling sheet larger than 8 inches according to claim 8 is characterized in that the Bow of the silicon carbide peeling sheet larger than 8 inches is 30~57μm, the Sori is 50~97μm, the damage layer depth is 60~95μm and the maximum surface crack step height is 50~70% of the damage layer depth.
10. The silicon carbide peeling sheet with a size of 8 inches or larger according to any one of claims 8 to 9 is characterized in that the silicon carbide peeling sheet with a size of 8 inches or larger is made by the silicon carbide peeling sheet processing method based on laser cracking as described in any one of claims 1 to 7.
11. A system for preparing a silicon carbide substrate larger than 8 inches by laser lift-off, characterized in that it comprises:

    The laser lift-off device comprises a crystal plane detection unit, an angle determination unit, an angle adjustment unit, a laser scanning unit, an external force applying unit, and a fixing unit for fixing and supporting a silicon carbide ingot.

    The laser scanning unit includes a first laser head capable of generating a first laser beam, and is configured to receive a first signal and start the first laser head to scan the silicon carbide ingot to form a to-be-peeled surface containing multiple cracks and extending along a first plane, wherein the first plane is always perpendicular to a first direction where the first laser beam is located, and the external force applying unit is configured to apply vibration to the to-be-peeled surface to obtain a silicon carbide peeling sheet;

    A thinning device having a grinding mechanism capable of thinning at least a portion of a single side of a single peeling sheet and/or thinning at least a portion of another single side of the single peeling sheet;

    A polishing device, comprising a workbench and an i-th polishing mechanism connected in series through the workbench, wherein the i-th polishing mechanism comprises an i-th polishing assembly, an i-th liquid supply assembly, an i-th cleaning assembly, and an i-th recovery assembly, wherein i is a natural number and traverses from 1 to n, and n is a natural number and is not less than 2;

    A cleaning device, having a cleaning mechanism capable of cleaning the polishing sheet to obtain a large-size silicon carbide substrate;

    Wherein, the large-size silicon carbide substrate is a silicon carbide substrate larger than 8 inches.
12. The system for laser stripping to prepare silicon carbide substrates larger than 8 inches according to claim 11 is characterized in that the crystal plane detection unit is arranged above the position of the silicon carbide ingot to be stripped, and is capable of detecting the (0001) crystal plane of the silicon carbide ingot to obtain crystal plane position information.
13. According to the system for laser stripping to prepare silicon carbide substrates larger than 8 inches according to claim 11, it is characterized in that the angle determination unit is configured to receive the crystal plane position information, and calculate the angle value between the crystal plane position information and the first plane, and determine whether the angle value meets the requirement of a preset angle value, and if so, output a first signal, and if not, output a second signal.
14. The system for preparing silicon carbide substrates larger than 8 inches by laser stripping according to claim 11 is characterized in that the angle adjustment unit includes an ingot angle adjustment mechanism capable of adjusting the angle of the silicon carbide ingot and/or a first laser beam angle adjustment mechanism capable of adjusting a first direction, and is configured to receive a second signal and start the ingot angle adjustment mechanism and/or the first laser beam angle adjustment mechanism.
15. The system for preparing silicon carbide substrates larger than 8 inches by laser stripping according to claim 14 is characterized in that the ingot angle adjustment mechanism includes a first adjustment component and a second adjustment component arranged below the fixing unit, the first adjustment component is configured to be able to adjust the silicon carbide ingot along the X-axis direction, the second adjustment component is configured to be able to adjust the silicon carbide ingot along the Y-axis direction, the X-axis direction and the Y-axis direction are located in the same plane and are perpendicular to each other or are parallel to two planes and are skewed and perpendicular to each other.
16. According to the system for laser stripping for preparing silicon carbide substrates larger than 8 inches according to claim 11, it is characterized in that the laser scanning unit also includes a second laser head capable of generating a second laser beam, and the second laser head is configured to enable the second laser beam to scan the silicon carbide ingot in a circumferential direction around the silicon carbide ingot; the second laser head is configured to be able to be controlled in conjunction with the first laser head, and to ensure that the second direction where the second laser beam is located is always within the first plane; the angle adjustment unit also includes a second laser beam angle adjustment mechanism capable of adjusting the second direction where the second laser beam is located, and is configured to be able to receive a second signal and start the second laser beam angle adjustment mechanism, so that the second direction is always within the first plane.
17. According to the system for preparing silicon carbide substrates larger than 8 inches by laser stripping as described in claim 11, it is characterized in that the grinding component includes a rough grinding wheel and a fine grinding wheel, the grinding wheel inclination angle set during the rough grinding process is 0°~0.5°, the feed speed is 5~30μm/min, the grinding wheel speed is 1000~4000rpm, and the grinding wheel mesh number is 2000~5000 mesh; preferably, the rough grinding wheel is set with a grinding wheel inclination angle of 0.1°~0.3°, a feed speed of 10~20μm/min, and a grinding wheel speed of 2000~2500rpm, grinding wheel mesh number 3000~4000 mesh; the grinding wheel inclination angle of the fine grinding wheel is -0.5°~0°, the feed speed is 3~20μm/min, the grinding wheel speed is 1000~3000rpm, and the grinding wheel mesh number is 15000~40000 mesh; preferably, the grinding wheel inclination angle of the fine grinding wheel is -0.3°~-0.1°, the feed speed is 5~15μm/min, the grinding wheel speed is 1500~2500rpm, and the grinding wheel mesh number is 20000~30000 mesh.
18. The system for preparing silicon carbide substrates larger than 8 inches by laser lift-off according to claim 11 is characterized in that the polishing mechanism includes the i-th polishing assembly fixed on the workbench and including the i-th polishing disk with an i-th polishing pad and the i-th polishing head; the i-th polishing head is located at the periphery of the i-th polishing disk, and during the polishing process, the i-th polishing head can fix the wafer to be polished, so as to realize the polishing operation of pressing one surface of the wafer to be polished on the i-th polishing disk; the i-th liquid supply assembly is used to inject polishing liquid into the i-th polishing disk; the i-th cleaning assembly is located on both sides of the polishing disk and can realize waste residue cleaning during the polishing process; the i-th recovery assembly is located below the polishing disk and can realize the recovery of waste liquid and waste residue after polishing; and the surface roughness of the wafer obtained by the i+1-th polishing mechanism is less than the surface roughness of the wafer obtained by the i-th polishing mechanism.
19. According to the system for preparing silicon carbide substrates larger than 8 inches by laser lift-off according to claim 11, it is characterized in that the SFQR of the silicon carbide substrate larger than 8 inches is not higher than 2μm, Bow is less than 25μm, Sori is less than 45μm, and the shape change before and after epitaxy is not higher than 10μm; preferably, the SFQR of the silicon carbide substrate is not higher than 1μm, Bow of the silicon carbide substrate is less than 10μm, Sori is less than 15μm, and the shape change before and after epitaxy is not higher than 5μm.
20. A method for low stress processing of silicon carbide substrates larger than 8 inches using a system for preparing silicon carbide substrates larger than 8 inches by laser lift-off as described in claims 11 to 19.