CN108345177B

CN108345177B - Device and method for measuring lamination error

Info

Publication number: CN108345177B
Application number: CN201710060271.XA
Authority: CN
Inventors: 陈彦良; 谢鸿志; 吴锴; 陈开雄; 柯志明
Original assignee: Taiwan Semiconductor Manufacturing Co TSMC Ltd
Current assignee: Taiwan Semiconductor Manufacturing Co TSMC Ltd
Priority date: 2017-01-24
Filing date: 2017-01-24
Publication date: 2020-06-30
Anticipated expiration: 2037-01-24
Also published as: CN108345177A

Abstract

The present disclosure provides a stacking error measurement apparatus and method. The device comprises a light source, an optical system, an objective lens and a detector. The light source is used for generating measuring light. The optical system is used to guide the measuring light into the objective lens. The objective lens is used for guiding the measuring light to a laminated mark, and simultaneously collecting the positive main pole diffraction light and the negative main pole diffraction light diffracted from the laminated mark onto a pupil plane of the objective lens. The detector is arranged on the pupil plane of the objective lens and is used for detecting the light intensity distribution of the positive and negative main pole diffracted light and subtracting the light intensity distribution of the positive and negative main pole diffracted light to obtain a lamination error signal of the lamination mark. Wherein the optical system comprises an aperture having at least one light-transmitting area whose position, size and/or shape is adjustable according to the position of the noise in the overlay error signal. The stacking error measuring device provided by the disclosure can improve the quality of the stacking error signal and can improve the accuracy of stacking error detection.

Description

Device and method for measuring lamination error

Technical Field

The present disclosure relates to semiconductor manufacturing technologies, and more particularly, to an overlay error (overlay error) measurement apparatus and method.

Background

In semiconductor manufacturing, photolithography is a critical step, which is directly related to the minimum feature size limit. Alignment and exposure are the most important techniques in photolithography, wherein the alignment is performed to transfer the mask pattern to the photoresist layer, since the semiconductor device (e.g., IC die) is formed by stacking a plurality of structural layers, if the exposure position is not aligned correctly, the patterns between the layers cannot be closely matched with the patterns of the original circuit design, which results in short circuit, open circuit, and poor electrical characteristics, thereby reducing the yield of the product and increasing the production cost.

The error in the overlay position of the pattern between the layers is also called overlay error. As the integration of devices becomes higher and higher, the number and complexity of photolithography increases, the tolerance of the overlay error is significantly reduced, and the requirement for the accuracy of the measurement of the overlay error becomes more stringent. Due to the limitation of imaging resolution limit, the conventional Image-based overlay measurement (IBO) based on imaging and Image recognition has been gradually unable to meet the accuracy requirement of the industry for measuring overlay error. The Diffraction-based overlay technique (DBO) is becoming the main means for measuring overlay error.

Although the existing DBO measurement technology meets the general measurement accuracy requirement, it still cannot satisfy all aspects. Accordingly, there is a need for an improved diffractive overlay error measurement apparatus and method.

Disclosure of Invention

Some embodiments of the present disclosure provide a stacking error measurement apparatus, comprising: an objective lens; a light source for generating a measuring light; an optical system for introducing the measurement light into the objective lens for introducing the measurement light onto a laminated mark while collecting main-positive diffraction light and main-negative diffraction light diffracted from the laminated mark onto a pupil plane of the objective lens; and a detector, set up on the pupil surface of the objective lens, is used for detecting the light intensity distribution of the above-mentioned positive, negative main pole diffraction light, and utilize the stated light intensity distribution of the positive, negative main pole diffraction light to subtract and get a lamination error signal of the lamination mark; the optical system includes a diaphragm having at least one light-transmitting region, and the position, size and/or shape of the light-transmitting region is adjustable according to the position of noise in the lamination error signal.

Some embodiments of the present disclosure provide a stacking error measurement apparatus, comprising: an optical system for guiding a measuring light from a light source to an objective lens for guiding the measuring light to a laminated mark while collecting positive and negative main diffracted lights diffracted from the laminated mark, wherein the optical system includes an aperture having at least one light-transmitting area and at least one non-light-transmitting area; and a detector for subtracting the light intensity distribution of the positive main-pole diffracted light and the negative main-pole diffracted light to obtain a lamination error signal of the lamination mark, and modulating the position, size and/or shape of the at least one light-transmitting area and the at least one non-light-transmitting area of the diaphragm according to the position of noise in the lamination error signal.

Some embodiments of the present disclosure provide a method for measuring overlay error, comprising: emitting a measuring light by a light source; guiding the measuring light into an objective lens through an optical system; guiding the measurement light onto a laminated mark through an objective lens, and collecting positive main-pole diffracted light and negative main-pole diffracted light diffracted from the laminated mark onto a pupil plane of the objective lens; detecting the light intensity distribution of the positive and negative main-pole diffracted light by a detector, and subtracting the light intensity distribution of the positive and negative main-pole diffracted light to obtain a reference lamination error signal of the lamination mark; modulating, by the detector, a position, a size, and/or a shape of at least one light-transmitting area of an aperture in the optical system according to a position of noise in the reference stack error signal; and detecting the light intensity distribution of the positive and negative main-pole diffracted light by a detector, and subtracting the light intensity distribution of the positive and negative main-pole diffracted light to obtain a formal lamination error signal of the lamination mark.

Drawings

Fig. 1 shows a schematic structural diagram of a stacking error detection apparatus according to some embodiments.

Fig. 2 is a schematic cross-sectional view of the overlay mark in fig. 1.

Fig. 3 shows a front view of the diaphragm of fig. 1.

Fig. 4 shows a light intensity distribution diagram of diffracted light of positive or negative order 1 detected by the detector in fig. 1.

FIG. 5 is a graph of a stack error signal obtained by subtracting the light intensity distributions of positive and negative 1 st order diffracted light, according to some embodiments.

FIG. 6 shows a schematic diagram of an active matrix liquid crystal module as an aperture according to some embodiments.

Fig. 7A and 7B are schematic diagrams illustrating the structure of each liquid crystal cell of the active matrix liquid crystal module in fig. 6 and the working principle of the active matrix liquid crystal module that allows or does not allow light to pass through.

FIG. 8 shows a block diagram of a control system of detector and aperture (active matrix liquid crystal module) composition according to some embodiments.

Fig. 9 is a schematic diagram of the structure of each micromirror unit using the micromirror array module as an aperture according to some embodiments.

FIG. 10 shows a flow diagram of a method of overlay error detection according to some embodiments.

Description of reference numerals:

10-a lamination error detection device;

11-a light source;

12-an optical system;

13-a collimating lens;

14-a filter plate;

15-aperture;

15A-a light-transmitting portion;

15B-the peripheral part;

16-a polarizing film;

17-a first lens;

18-field diaphragm;

19 to a second lens;

20-spectroscope;

21-objective lens;

22 to a lens group;

23-detector;

23A-a processing unit;

71 to a first polarizing plate;

72 to the first electrode;

72A-an alignment film;

73-the liquid crystal layer;

74-a second electrode;

74A-alignment film;

75 to a second polarizing plate;

80-position data;

91-micro lens;

92-a support member;

93-a control circuit;

151 to panel units;

152-a time schedule controller;

153-scanning driving unit;

154 to a data driving unit;

200-a lamination error detection method;

201-206 step;

b, testing light;

b1-ray;

d-position error;

D₁dn-data drive signal;

g1 lower grating structure;

g2-upper grating structure;

l1 front layer;

l2-equivalent layer;

l3 intermediate material layer;

m-stacking marks;

r1-light-transmitting region;

r2-opaque region;

s-base material;

S₁sm to Scan drive signals;

sd-data control signal;

ss-scanning control signals;

t-inclination angle;

u-liquid crystal unit;

u' -micro-mirror unit;

v-voltage.

Detailed Description

The following disclosure provides many different embodiments, or examples, for implementing different features of the disclosure. The following disclosure describes specific examples of components and arrangements thereof to simplify the description. Of course, these specific examples are not intended to be limiting. For example, if embodiments describe a first feature formed over or on a second feature, that may include the first feature being in direct contact with the second feature, embodiments may also include additional features formed between the first and second features such that the first and second features are not in direct contact.

Spatially relative terms, such as "below," "lower," "above," "upper," and the like, may be used hereinafter in the context of the description to facilitate describing a relationship between one element or feature and another element(s) or feature(s) in the figures. These spatially relative terms are intended to encompass the possible use or operation of the device in the figures in addition to the orientation depicted in the figures.

The same reference numbers and/or letters may be repeated in the various embodiments below for simplicity and clarity, and are not intended to limit the particular relationships between the various embodiments and/or structures discussed.

The terms first and second, etc. are used hereinafter for clarity in explanation, and are not used to correspond to or limit the claims. The terms first feature and second feature are not intended to be limited to the same or different features.

In the drawings, the shape or thickness of the structures may be exaggerated to simplify or facilitate labeling. It is to be understood that elements not specifically described or illustrated may exist in various forms well known to those skilled in the art.

Referring first to fig. 1, a schematic structural diagram of a stacking error detection apparatus 10 according to some embodiments of the present disclosure is shown. It should be noted that the overlay error detection apparatus 10 is a Diffraction-based overlay error measurement apparatus for detecting an error in a pattern overlay position between layers of a semiconductor device. For example, when the uppermost material layer (also called current layer) on a semiconductor substrate (e.g., a silicon wafer) is subjected to a photolithography process, the overlay error detection apparatus 10 can detect at least one overlay mark simultaneously formed on the current layer and an underlying material layer (also called a previous layer) by diffraction light, thereby determining the overlay error between the patterns of the current layer and the previous layer.

As can be seen from fig. 1, the stacking error detecting apparatus 10 includes a light source 11, an optical system 12, an objective lens 21, and a detector 23.

The light source 11 is used to generate a measuring light. In some embodiments, the light source 11 may be a white light source, a broadband light source, or a composite light source composed of a plurality of monochromatic lights. In some embodiments, the white light source may be selected from, for example, Xe light sources, broadband light sources that generate light including ultraviolet, visible, infrared, or combinations thereof, and composite light sources that are derived from multiple laser beams of different wavelengths by mixing.

The optical system 12 is used to guide the measuring light emitted by the light source 11 into the objective 21. In particular, the optical system 12 may comprise, in order along the propagation direction of the measurement light: a collimating lens 13, a filter 14, a polarizer 16, a first lens 17, a second lens 19 and a beam splitter 20. The collimator lens 13 is used to collimate the measurement light. The filter 14 is used to pass light of a single wavelength. In some embodiments, filter 14 is monochromatic, but is not so limited. In addition, when the light source 11 uses a laser light source, the filter 14 can be omitted. The polarizing plate 16 is used to generate linearly polarized light. In some embodiments, polarizing beamsplitters (polarizing beamsplitters) may also be used in place of polarizer 16. The first and

second lenses

17 and 19 are, for example, focusing lenses for focusing light. The beam splitter 20 is used to guide and inject the measurement light into the objective 21, and in some embodiments, the beam splitter 20 may be a prism, a grating, or a combination of a prism and a grating. Further, the optical system 12 may further include a lens group 22 for condensing light between the objective lens 21 and the detector 23.

Furthermore, the optical system 12 includes an aperture 15 and a field stop 18 for modulating the measuring light into incident light symmetrical with respect to the center of the optical axis of the objective lens 21. Specifically, in the parallel optical system, an aperture 15 (also called an aperture stop) is disposed in front of the polarizer 16 for generating a light spot satisfying the shape requirement of the objective lens 21 for the incident light, that is, determining the shape of the image. In some embodiments, the light-transmitting portion 15A of the diaphragm 15 may be designed to be circular (as shown in fig. 3), square, rectangular, slit, or any polygon. The field stop 18 is disposed between the first lens 17 and the second lens 19 for generating a light spot satisfying the size requirement of the incident light, i.e. determining the imaging range.

Referring to fig. 1 and 2, the objective lens 21 is used to guide the measuring light B to an overlay mark M. In some embodiments, the overlay mark M is composed of upper and lower grating structures (as shown in fig. 2) formed on the semiconductor substrate S. Here, the grating structure refers to a periodic structure known in the art. The lower grating structure G1 may be formed on a material layer (also referred to as a front layer L1) on the semiconductor substrate S by processes such as exposure, development, and etching. The front layer L1 is not limited to being directly on the semiconductor substrate S, and other structural layers may be formed therebetween. The upper grating structure G2 is usually formed on the top material layer (also referred to as layer L2) after the next process such as exposure, development, etching, etc. In addition, at least one intermediate material layer L3 is disposed between the upper and lower grating structures G1 and G2. The stacking error refers to the position error d (shown in FIG. 2) between the upper and lower grating structures G1 and G2. By detecting the lamination error of the lamination mark M, the error in the position of the pattern overlay between the layer L2 and the previous layer L1 can be interpreted.

It should be appreciated that, in order to detect the overlay error between the corresponding patterns of the current layer L2 and the previous layer L1, an overlay mark M typically includes a plurality of sets of two-layer grating structures respectively arranged along a first direction (e.g., X-direction) and a second direction (e.g., Y-direction perpendicular to the X-direction).

With continued reference to fig. 1, the measurement light can be diffracted on the laminated mark M, and the objective lens 21 can collect diffracted lights from the laminated mark M, especially diffracted lights of main poles other than the central main pole diffracted light (i.e. positive main pole diffracted light and negative main pole diffracted lights, such as positive 1-order diffracted light, negative 1-order diffracted light, positive 2-order diffracted light, negative 2-order diffracted light, etc.), and collect the diffracted lights on a pupil plane (not shown) of the objective lens 21.

The detector 23 is disposed on the pupil plane of the objective lens 21, and detects optical signals of the positive and negative main-pole diffracted lights from the lamination mark M. In some embodiments, the detector 23 may employ a photosensitive coupled device (CCD) or a Complementary Metal Oxide Semiconductor (CMOS).

It should be noted that the embodiments described herein can calculate the lamination error of the lamination mark M by using only the optical signals of the positive 1 st order diffracted light and the negative 1 st order diffracted light (such as the two beams shown in fig. 1), but the higher order diffracted light (i.e. above 2 th order) can also be used to detect the lamination error.

Referring to fig. 4, the optical signals of the positive 1 st-order diffracted light and the negative 1 st-order diffracted light detected by the detector 23 each have a circular light intensity distribution with a shape corresponding to the shape of the light-transmitting portion 15A of the diaphragm 15.

When the position error d between the upper and lower grating structures G1 and G2 of the lamination mark M is 0, the optical signals of the positive 1 st order diffracted light and the negative 1 st order diffracted light detected by the detector 23 may have uniform light intensity distribution; in contrast, when the position error d between the upper and lower grating structures G1 and G2 of the stack mark M is not 0, the light intensity distributions of the optical signals of the positive 1 st order diffracted light and the negative 1 st order diffracted light detected by the detector 23 are different. In this way, the detector 23 can obtain a lamination error signal of the lamination mark M by comparing the difference between the light intensity distributions of the positive 1 st order diffracted light and the negative 1 st order diffracted light (i.e., by using the result of subtracting the light intensity distributions of the positive 1 st order diffracted light and the negative 1 st order diffracted light). The lamination error of the lamination mark M can be calculated by analyzing the light intensity distribution of the lamination error signal (as shown in fig. 5) through a processing unit (not shown) in the detector 23.

However, as can be seen from fig. 5, some noise N (or signal with very low intensity) may appear in a partial region of the above-mentioned stack error signal (such as the circled region in the figure, which is also called bad area), which may interfere with the interpretation of the stack error signal and cause the accuracy of the detection of the stack error to be affected.

It has been found that the noise N is mainly caused by the light incident on the laminated mark M at a specific angle, and the intermediate material layer L3 between the upper and lower grating structures G1 and G2 is prone to total reflection (as shown by the light B1 in fig. 2) or energy is absorbed, so that the noise N cannot be detected well by the detector 23. Therefore, if the portion of the test light that generates the noise N is directly blocked by the aperture 15, the noise N in the stack error signal can be effectively removed to prevent the noise N from interfering with the interpretation of the stack error signal, thereby improving the accuracy of the detection of the stack error.

To achieve the above, some embodiments of the present disclosure employ a special aperture 15 as shown in fig. 6, 7A-7B, and 9. In some embodiments, the aperture 15 may have at least one transparent region, and the position, size and/or shape of the transparent region may be adjustable according to the position of the noise N in the lamination error signal.

It should be noted that, since the shape (circular shape, see fig. 5) of the light intensity distribution of the lamination error signal detected by the detector 23 corresponds to the shape of the light transmission portion 15A of the diaphragm 15, the position of the noise N in the lamination error signal may also correspond to the relative position in the light transmission portion 15A of the diaphragm 15 (i.e., have a matching relationship).

By this feature, the position, size and/or shape of at least one transparent area of the diaphragm 15 (within the transparent portion 15A) can be modulated according to the position of the noise N in the lamination error signal (or the position, size and/or shape of at least one non-transparent area of the diaphragm 15) so that part of the test light that generates the noise N is directly blocked by the diaphragm 15 and the noise N in the lamination error signal can be removed.

Referring to fig. 6, 7A and 7B, in some embodiments, the diaphragm 15 is an active matrix (active matrix) liquid crystal module having a plurality of liquid crystal cells U arranged in a matrix.

Each liquid crystal unit U sequentially includes, in the direction in which the measurement light passes through the aperture 15: a first polarizer 71, a first electrode 72, a liquid crystal layer 73, a second electrode 74 and a second polarizer 75. More specifically, the liquid crystal layer 73 is disposed between the first and

second electrodes

72 and 74, and

alignment films

72A and 74A are respectively formed on the inner sides of the first and

second electrodes

72 and 74. The alignment grooves of the

alignment films

72A and 74A are perpendicular to each other, so that the alignment direction of the liquid crystal molecules in the liquid crystal layer 73 (in the absence of an electric field) can be twisted by 90 degrees from one end of the alignment film 72A to one end of the alignment film 74A (as shown in fig. 7A). The first polarizing plate 71 and the second polarizing plate 75 are disposed outside the first and

second electrodes

72 and 74, respectively, and have polarization directions perpendicular to each other. In addition, each liquid crystal cell U includes a Thin Film Transistor (TFT) substrate (not shown) for outputting a voltage V to control the alignment direction of liquid crystal molecules.

As can be seen from fig. 7A, when no voltage is applied between the first and

second electrodes

72 and 74, the measurement light passing through the liquid crystal layer 73 may be rotated by 90 degrees with the twist of the liquid crystal molecules and passes through the vertical first and

second polarizers

71 and 75. As can be seen from fig. 7B, when a voltage V is applied between the first and

second electrodes

72 and 74, liquid crystal molecules (e.g., positive liquid crystal molecules) in the liquid crystal layer 73 can be aligned along the electric field direction, and the measuring light can not rotate and can not pass through the second polarizer 75.

It should be understood that the structure and control manner of each liquid crystal unit U of the diaphragm 15 are not limited to the above-described embodiments. For example, in some embodiments, the polarization directions of the first and

second polarizers

71 and 75 may be parallel to each other, and the measurement light that rotates 90 degrees with the twist of the liquid crystal molecules cannot pass through the second polarizer 75 when no voltage is applied between the first and

second electrodes

72 and 74, and the measurement light can pass through the second polarizer 75 when a voltage V is applied between the first and

second electrodes

72 and 74.

Thus, by controlling the voltage applied between the first and

second electrodes

72 and 74 through the TFT substrate, the orientation of the liquid crystal molecules in each liquid crystal cell U can be controlled to allow or not allow light to pass through. In this way, the positions, sizes and/or shapes of the at least one light-transmitting region R1 and the at least one non-light-transmitting region R2 within the range of the light-transmitting portion 15A (inside the dotted circle) of the diaphragm 15 can be (arbitrarily) adjusted, wherein the light-transmitting region R1 corresponds to the state where the liquid crystal unit U allows light to pass (as shown in fig. 7A), and the non-light-transmitting region R2 corresponds to the state where the liquid crystal unit U does not allow light to pass (as shown in fig. 7B).

It should be noted that the liquid crystal unit U at the peripheral portion 15B of the diaphragm 15 (i.e., the portion outside the light-transmitting portion 15A) can be normally controlled to be in a state of not allowing light to pass (as shown in fig. 7B). Alternatively, in some embodiments, only the portion of the light-transmitting portion 15A of the aperture 15 is an active matrix liquid crystal module, and the peripheral portion 15B of the aperture 15 may be a mechanical light barrier to save energy consumption.

Further, in some embodiments, the detector 23 can control and modulate the position, size and/or shape of the at least one light-transmitting region R1 and the at least one non-light-transmitting region R2 of the iris 15 (active matrix liquid crystal module) according to the detected position of the noise in the lamination error signal.

Referring to FIG. 8, a block diagram of a control system including the detector 23 and the aperture 15 according to some embodiments is shown. For example, when the detector 23 detects a lamination error signal (light intensity distribution) of the lamination mark M, a processing unit 23A in the detector 23 can obtain a distribution position of the noise therein by analyzing the lamination error signal, for example, the processing unit 23A of the detector 23 can obtain position coordinates of the light intensity higher and lower than a specific value from the light intensity distribution of the lamination error signal (as shown in fig. 5), that is, position coordinates of the normal signal portion and the noise in the lamination error signal. Then, the processing unit 23A generates a position data 80 including position coordinates corresponding to the light-transmitting region R1 and the non-light-transmitting region R2 of the diaphragm 15 by arithmetic transformation.

The detector 23 is electrically connected to the aperture 15 (active matrix liquid crystal module) by wire (e.g., wire, cable or fiber) or wirelessly (e.g., bluetooth, wifi or Near Field Communication (NFC) transmission). The diaphragm 15 includes a panel unit 151, a Timing Controller (TCON) 152, a scan driving unit 153, and a data driving unit 154. In some embodiments, the panel unit 151 has liquid crystal cells (also referred to as display units) arranged in a plurality of columns and a plurality of rows, and the structure of each liquid crystal cell can be referred to as shown in fig. 7A and 7B, for example. The timing controller 152 is configured to receive the position data 80 generated by the processing unit 23A of the detector 23, and provide a scan control signal Ss and a data control signal Sd to the scan driving unit 153 and the data driving unit 154, respectively. The scan driving unit 153 and the data driving unit 154 are used for generating driving signals according to the control signals, so as to control the operation of the panel unit 151 by, for example, writing voltage data of a Thin Film Transistor (TFT) to each liquid crystal cell of the panel unit 151.

More specifically, in some embodiments, the scan driving unit 153 may generate the scan driving signal S based on the scan control signal Ss according to a certain column scan order in a time period₁Sm is applied to the scan lines of each column of liquid crystal cells. As described above, the scanning drive signal S₁Sm is applied to the gate electrode (not shown) of the TFT corresponding to each liquid crystal cell to turn on the corresponding TFT by applying a gate voltage so that the voltage data of the corresponding liquid crystal cell can be written for the data driving unit 154.

In addition, in some embodiments, the data driving unit 154 is configured to write voltage data to the liquid crystal cell array based on the data control signal Sd in each time period. For example, the data driving unit 154 may simultaneously drive the data driving signals D₁Dn is applied to the data lines of the rows of liquid crystal cells, thereby controlling the magnitude or time of the voltage applied to the source of each TFT.

As described above, the embodiments of fig. 6 to 8 can correspondingly control each liquid crystal unit U to be in a state of allowing or not allowing light to pass through (as shown in fig. 7A and 7B) based on the position of the noise in the lamination error signal. For example, when the processing unit 23A of the detector 23 analyzes the lamination error signal to obtain the distribution position of the noise therein, the processing unit can further obtain a position data 80 including the position coordinates of the light-transmitting region R1 and the non-light-transmitting region R2 corresponding to the diaphragm 15 by operation conversion. Thus, the detector 23 can further control the light-transmitting or non-light-transmitting state of each liquid crystal unit U of the diaphragm 15 (by applying or not applying a voltage) based on this position data 80, and make the positions of the light-transmitting region R1 and the non-light-transmitting region R2 of the diaphragm 15 (within the range of the light-transmitting portion 15A) correspond to the positions of the normal signal and the noise in the lamination error signal, respectively, so that part of the test light that would generate the noise is directly blocked by the diaphragm 15. Therefore, the noise in the lamination error signal can be automatically and accurately removed, so that the quality of the lamination error signal is improved, and the accuracy of the lamination error detection is improved.

In some embodiments, the aperture 15 may also be a micro-lens (micro-lens) array module having a plurality of micro-lens units arranged in a matrix. As shown in fig. 9, each micromirror unit U' includes a micromirror 91, a supporting member 92 for supporting and allowing the micromirror 91 to move, and a control circuit 93 electrically connected to the supporting member 92. The supporting member 92 is an actuating member and can change the inclination angle T of the micromirror 91 according to the voltage applied by the control circuit 93. When the inclination angle T of the micromirror 91 exceeds a certain angle, the light can travel in a different direction such that the light does not pass through the micromirror unit U' (as shown in the figure). That is, by changing the inclination angle T of the micro-mirror 91, the effect of allowing or not allowing light to pass through the micro-mirror unit U' can also be achieved.

Therefore, in some embodiments, the aperture 15 in the embodiment shown in fig. 6 to 8 can be changed to a micromirror array module, and the inclination angle T of the micromirror 91 in each micromirror unit U' of the micromirror array module is controlled to allow or not allow light to pass through, so that the position, size and/or shape of the transparent area and the non-transparent area of the aperture 15 can be adjusted, thereby achieving the purpose of removing noise in the lamination error signal.

FIG. 10 shows a flow diagram of a method 200 of overlay error detection according to some embodiments. In step 201, a measurement light is emitted by a light source. In step 202, measurement light is directed into an objective lens through an optical system. In step 203, measurement light is directed onto an overlay mark through an objective lens, and positive and negative main diffracted light diffracted from the overlay mark is collected onto a pupil plane of the objective lens. In step 204, the light intensity distributions of the positive and negative main-pole diffracted lights are detected by a detector, and a reference lamination error signal of the lamination mark is obtained by subtracting the light intensity distributions of the positive and negative main-pole diffracted lights. In step 205, the position, size and/or shape of at least one transparent area of an aperture in the optical system is modulated by the detector according to the position of the noise in the reference overlay error signal. In step 206, the light intensity distributions of the positive and negative main-pole diffracted lights are detected by a detector, and the light intensity distributions of the positive and negative main-pole diffracted lights are subtracted to obtain a formal lamination error signal of the lamination mark.

It is to be understood that the steps of the above-described stack error detection method are merely exemplary, and the stack error detection method in some embodiments may include other steps and sequences of steps.

In summary, the embodiments of the present disclosure have the following advantages: since the aperture stop (aperture stop) in the optical system has at least one transparent region, and the position, size and/or shape of the transparent region is adjustable according to the position of the noise in the lamination error signal detected by the detector, the angle at which the test light is incident on the lamination mark can be changed by adjusting the position, size and/or shape of the transparent region (or the non-transparent region) of the aperture stop, and the noise in the lamination error signal can be further removed. Therefore, the quality of the lamination error signal can be improved, and the accuracy of the lamination error detection can be improved.

According to some embodiments, a stacking error measurement apparatus is provided, including an objective lens, a light source, an optical system, and a detector. The light source is used for generating measuring light. The optical system is used to guide the measuring light into the objective lens. The objective lens is used for guiding the measuring light to a laminated mark, and simultaneously collecting positive main-pole diffracted light and negative main-pole diffracted light diffracted from the laminated mark onto a pupil plane of the objective lens. The detector is arranged on the pupil plane of the objective lens and is used for detecting the light intensity distribution of the positive and negative main pole diffracted light and subtracting the light intensity distribution of the positive and negative main pole diffracted light to obtain a lamination error signal of the lamination mark. The optical system includes a diaphragm having at least one light-transmitting region, and the position, size and/or shape of the light-transmitting region is adjustable according to the position of noise in the lamination error signal.

According to some embodiments, the overlay error signal has a light intensity distribution with a shape corresponding to a shape of a light-transmitting portion of the aperture.

According to some embodiments, the detector is electrically connected to the aperture and modulates the position, size and/or shape of at least one transparent area and at least one non-transparent area of the aperture according to the position of noise in the lamination error signal.

According to some embodiments, the aperture is an active matrix liquid crystal module, and the position, size and/or shape of the at least one transparent region and the at least one non-transparent region of the aperture can be adjusted by controlling the orientation of liquid crystal molecules in at least one liquid crystal cell of the active matrix liquid crystal module to allow or not allow light to pass through.

According to some embodiments, the aperture is a micromirror array module, and the position, size and/or shape of at least one transparent area and at least one non-transparent area of the aperture can be adjusted by controlling the tilt angle of the micromirror in at least one micromirror unit of the micromirror array module to allow or not allow light to pass through.

According to some embodiments, the optical system comprises, in order along the propagation direction of the measurement light: a collimating lens, a filter, an aperture, a first lens, a field stop, a second lens and a beam splitter.

According to some embodiments, the positive and negative host diffracted lights are positive 1-order diffracted light and negative 1-order diffracted light.

According to some embodiments, the overlay mark is composed of two layers of grating structures located on a current layer and a previous layer of a substrate.

According to some embodiments, a stacking error measurement apparatus is provided that includes an optical system and a detector. The optical system is used for guiding a measuring light from a light source to an objective lens, the objective lens is used for guiding the measuring light to a laminated mark and simultaneously collecting positive main pole diffraction light and negative main pole diffraction light diffracted from the laminated mark, and the optical system comprises an aperture having at least one light-transmitting area and at least one non-light-transmitting area. The detector is used for subtracting the light intensity distribution of the positive main-pole diffracted light and the negative main-pole diffracted light to obtain a lamination error signal of the lamination mark, and the position, the size and/or the shape of at least one light-transmitting area and at least one non-light-transmitting area of the diaphragm are modulated according to the position of noise in the lamination error signal.

According to some embodiments, there is provided a method of overlay error measurement, comprising: emitting a measuring light by a light source; guiding the measuring light into an objective lens through an optical system; guiding the measurement light onto a laminated mark through an objective lens, and collecting positive main-pole diffracted light and negative main-pole diffracted light diffracted from the laminated mark onto a pupil plane of the objective lens; detecting the light intensity distribution of the positive and negative main-pole diffracted light by a detector, and subtracting the light intensity distribution of the positive and negative main-pole diffracted light to obtain a reference lamination error signal of the lamination mark; modulating, by the detector, a position, a size, and/or a shape of at least one light-transmitting area of an aperture in the optical system according to a position of noise in the reference stack error signal; and detecting the light intensity distribution of the positive and negative main-pole diffracted light by a detector, and subtracting the light intensity distribution of the positive and negative main-pole diffracted light to obtain a formal lamination error signal of the lamination mark.

While the present disclosure has been described with reference to the foregoing embodiments, it is not intended to be limited thereto. Those skilled in the art to which this disclosure pertains will readily appreciate that numerous modifications and adaptations may be made without departing from the spirit and scope of the present disclosure. Therefore, the protection scope of the present disclosure should be determined by the claims.

Claims

1. A stacking error measuring apparatus, comprising:

an objective lens;

a light source for generating a measuring light;

an optical system for introducing the measurement light into the objective lens for introducing the measurement light onto a laminated mark while collecting positive and negative main-pole diffracted light diffracted from the laminated mark onto a pupil plane of the objective lens; and

a detector, disposed on the pupil plane of the objective lens, for detecting the light intensity distribution of the positive and negative main-pole diffracted lights, and subtracting the light intensity distribution of the positive and negative main-pole diffracted lights to obtain a lamination error signal of the lamination mark;

the optical system comprises an aperture having at least one light-transmitting area, wherein the position, size and/or shape of the light-transmitting area is adjustable according to the position of the noise in the lamination error signal.

2. The stacking error measuring device of claim 1, wherein the stacking error signal has a light intensity distribution with a shape corresponding to a shape of a light-transmitting portion of the aperture.

3. The stacking error measuring apparatus of claim 1 or 2, wherein the detector is electrically connected to the aperture and modulates the position, size and/or shape of the at least one transparent area and the at least one non-transparent area of the aperture according to the position of noise in the stacking error signal.

4. The apparatus according to claim 3, wherein the aperture is an active matrix liquid crystal module, and the position, size and/or shape of the at least one transparent region and the at least one non-transparent region of the aperture can be adjusted by controlling the orientation of liquid crystal molecules in at least one liquid crystal cell of the active matrix liquid crystal module to allow or not allow light to pass through.

5. The overlay error measurement apparatus according to claim 3, wherein the aperture is a micromirror array module, and the position, size and/or shape of the at least one transparent area and the at least one non-transparent area of the aperture can be adjusted by controlling the tilt angle of the micromirror in at least one micromirror unit of the micromirror array module to allow or not allow light to pass through.

6. The stacking error measuring device of claim 1 or 2, wherein the optical system comprises, in order along the propagation direction of the measuring light: a collimating lens, a filter, the aperture, a first lens, a field stop, a second lens and a beam splitter.

7. The overlay error measurement device of claim 1 or 2, wherein the positive and negative host diffracted lights are positive 1-order diffracted light and negative 1-order diffracted light.

8. The stacking error measuring device of claim 1 or 2, wherein the stacking mark is composed of two grating structures of a current layer and a previous layer on a substrate.

9. A stacking error measuring device, comprising:

an optical system for directing a measurement light from a light source to an objective lens for directing the measurement light onto a laminated mark while collecting positive and negative main diffracted lights diffracted from the laminated mark, wherein the optical system comprises an aperture having at least one light-transmitting area and at least one non-light-transmitting area; and

and the detector is used for subtracting the light intensity distribution of the positive main-pole diffracted light from the light intensity distribution of the negative main-pole diffracted light to obtain a lamination error signal of the lamination mark, and modulating the position, the size and/or the shape of the at least one light-transmitting area and the at least one non-light-transmitting area of the diaphragm according to the position of noise in the lamination error signal.

10. A method of overlay error measurement, comprising:

emitting a measuring light by a light source;

directing the measurement light through an optical system into an objective lens;

directing the measurement light through the objective lens onto a laminated mark and collecting positive and negative main diffracted light diffracted from the laminated mark onto a pupil plane of the objective lens;

detecting the light intensity distribution of the positive main-pole diffracted light and the negative main-pole diffracted light by a detector, and subtracting the light intensity distribution of the positive main-pole diffracted light and the negative main-pole diffracted light to obtain a reference lamination error signal of the lamination mark;

modulating, by the detector, a position, a size, and/or a shape of at least one light-transmissive region of an aperture in the optical system according to a position of noise in the reference stack error signal; and

the light intensity distribution of the positive main-pole diffracted light and the negative main-pole diffracted light is detected by the detector, and the light intensity distribution of the positive main-pole diffracted light and the negative main-pole diffracted light is subtracted to obtain a formal lamination error signal of the lamination mark.