Substrate Lateral Displacement Monitoring and Lateral Alignment System and Method

Abstract

The present invention relates to the field of substrate lateral displacement measurement and lateral alignment, and provides an interferometric scattering microscopy-based method. By performing microscopic imaging on the substrate surface, recording the speckle information on the substrate surface, and obtaining the position information of the substrate at different times, the lateral displacement monitoring of the substrate is realized. Further, according to the monitored lateral displacement information of the substrate, the substrate is moved to a specified position to achieve lateral alignment of the substrate. Its characteristics are that it does not rely on markers and has low requirements for illumination stability, and can achieve sub-nanometer precision lateral displacement monitoring and lateral alignment of the substrate.

Description

Technical Field

[0001] This article relates to the field of substrate lateral displacement monitoring and lateral alignment, specifically to a field of substrate lateral displacement monitoring and lateral alignment based on interferometric scattering microscopy technology. Background Art

[0002] Sub-nanometer precision substrate lateral displacement monitoring and lateral alignment technologies are of great significance and have wide applications. For example, fluorescence super-resolution imaging that observes for a long time and superimposes images requires high-precision lateral displacement monitoring and real-time alignment to avoid sample drift and reduce resolution; in semiconductor processing, when processing or measuring the same area of a silicon wafer in different processes, high-precision lateral alignment also needs to be ensured. Currently, commonly used substrate lateral displacement monitoring and lateral alignment technologies all rely on markers such as defects, particulate matter, or pattern structures on the substrate surface, and there is still a lack of related technologies that do not rely on markers.

[0003] In various substrates in actual production, such as silicon wafers, glass products, mica, metal products, organic materials, etc., there are nanometer-level or sub-nanometer-level undulations on the surface. Utilizing this characteristic, the present invention discloses a substrate lateral displacement monitoring and lateral alignment system and method.

[0004] The present invention uses interferometric scattering microscopy technology to image the substrate surface, obtains an interference contrast image containing a large number of speckles, performs cross-correlation function analysis on the interference contrast images at each moment, and monitors the lateral displacement of the substrate according to the central position of the cross-correlation function. Further, according to the obtained substrate lateral displacement amount, the substrate is moved to a specified position for lateral alignment.

[0005] The system and method disclosed by the present invention are based on interferometric scattering microscopy technology. Interferometric scattering microscopy technology is an optical microscopy technology developed in recent years, which has the characteristics of being label-free, high-precision positioning, and high sensitivity. Its sensitivity is sufficient to detect single molecules and has been widely used in scientific research. Interferometric scattering microscopy technology simultaneously collects the illumination light reflected or transmitted by the sample substrate surface, i.e., the reference light, and the scattered light generated by the nanometer-level or sub-nanometer-level undulations, particles, or structures on the substrate surface. The reference light and the scattered light interfere with each other to form a detectable interference image. Let represent the electric field of the scattered light, and let represent the electric field of the reference light. Then the detected light intensity can be expressed as

[0006]

[0007] The three terms in the above formula respectively represent the reference light intensity the scattered light intensity and the interference term light intensity (I interfere = 2Es E r cos φ). Where φ = φ r -φ s represents the phase difference between the reference light and the scattered light. For I s much smaller than I r case, ignoring the small quantity I s , the interference contrast is obtained

[0008]

[0009] In interference scattering microscopy, the optical image I of the substrate region S is collected respectively as the total light intensity, and the optical images of multiple regions of the substrate are collected and averaged as I average as the light intensity of the reference light, and the operation C = (I - I average ) / I average is performed to obtain the interference contrast image C of the region S. The value of each pixel of the contrast image C is the interference contrast c of the corresponding pixel. Thus, the interference contrast image of any region on the substrate surface can be obtained. There are nanoscale or sub-nanoscale undulations on the substrate surface, and the interference contrast image of each region contains unique and repeatable speckles.

[0010] Interference contrast images are collected for a specific region of the substrate at different times respectively to achieve the monitoring of the lateral displacement of the substrate. For example, the interference contrast image at time t1 is denoted as C(t1), and the contrast image obtained at time t2 is denoted as C(t2). Cross-correlation function analysis is performed on the two, that is

[0011] XC(t1, t2, Δx, Δy) = ∫∫C(t1, x, y)C(t2, x + Δx, y + Δy)dxdy

[0012] By fitting the center position (Δx0, Δy0) of the cross-correlation function XC, the displacement of the substrate at time t2 relative to that at time t1 can be monitored as (-Δx0, -Δy0), thus achieving the monitoring of the lateral displacement of the substrate.

[0013] Furthermore, according to the monitored displacement information, the substrate is moved to a specified position. For example, the substrate is moved to the position it was at time t1.

[0014] As described above, the substrate lateral displacement monitoring and lateral alignment system and method disclosed by the present invention do not require marking the substrate. Summary of the Invention

[0015] The technical problem to be solved by the present invention is to provide a system and method for realizing the monitoring of the lateral displacement and lateral alignment of a substrate without relying on markers.

[0016] To solve the above problems, the present invention first proposes a substrate lateral displacement monitoring and lateral alignment system, comprising:

[0017] A light source assembly for providing an illumination beam;

[0018] A microscopic system for guiding the illumination beam to irradiate the surface of the substrate, forming a detection beam, and guiding the detection beam to a detector;

[0019] A detector for generating an optical image;

[0020] A displacement adjustment device for carrying the substrate and adjusting the position of the substrate;

[0021] A computer processing system for processing the optical image, generating an interference contrast image, extracting the displacement information of the substrate, and controlling the displacement adjustment device.

[0022] The detection beam includes a reference beam directly reflected or transmitted by the substrate, and also includes a scattered beam generated by nano-scale or sub-nano-scale undulations on the surface of the substrate, particles or structures on the surface of the substrate.

[0023] The interference contrast image refers to an image formed by the interference of the reference beam and the scattered beam.

[0024] The computer processing system performs a cross-correlation function analysis on the interference contrast images at different times, fits the central position of the cross-correlation function, extracts the positions of the substrate at different times, and obtains the lateral displacement information of the substrate.

[0025] The computer processing system controls the displacement adjustment device according to the monitored displacement information to move the substrate to a specified position.

[0026] The microscopic system further includes a spatial filter for attenuating the intensity of the reference beam and improving the interference contrast.

[0027] According to the substrate lateral displacement monitoring and lateral alignment system, the present invention proposes a substrate lateral displacement monitoring and lateral alignment method, comprising the following steps:

[0028] The light source assembly emits an illumination beam;

[0029] The illumination beam is guided by the microscopic system to irradiate the surface of the sample, forming a detection beam, and the detection beam is guided to the detector to form an optical image; the detection beam includes a reference beam directly transmitted through the surface of the substrate, and also includes a scattered beam generated by sub-nano-scale or nano-scale undulations on the surface of the substrate, particles or structures on the surface of the substrate;

[0030] The optical image is processed into an interference contrast image formed by the interference of the reference beam and the scattered beam;

[0031] Perform cross - correlation function analysis on the interference contrast images at different times, fit the center position of the cross - correlation function, extract the positions of the substrate at different times, and monitor the lateral displacement of the substrate;

[0032] According to the monitored lateral displacement information, control the displacement adjustment device to move the substrate to the specified position for alignment.

[0033] Furthermore, perform spatial filtering in the microscopic system, attenuate the reference beam, and enhance the interference contrast.

[0034] The above - mentioned substrate can be any substrate, including but not limited to silicon wafers, glass products, mica, organic materials, metal products, etc.

[0035] The substrate lateral displacement monitoring and lateral alignment system and method disclosed in the present invention are based on the fact that the nano - scale or sub - nano - scale undulations on the substrate surface cause speckles in the interference contrast image, and the speckles in different regions have uniqueness and repeatability. By tracking the movement of the speckles, the lateral displacement of the substrate can be monitored. Furthermore, according to the monitored displacement information, control the displacement adjustment device to move the substrate to the specified position to achieve lateral alignment of the substrate.

[0036] Furthermore, add a spatial filter in the microscopic system to attenuate the intensity of the reference light, enhance the interference contrast of the speckles, improve the signal - to - noise ratio of the system, and achieve higher - precision lateral displacement monitoring accuracy and lateral alignment.

[0037] Compared with the prior art, the present invention mainly has the following advantages:

[0038] Firstly, the present invention does not rely on markers;

[0039] Secondly, the interference contrast image measured by the present invention is extracted from the ratio of the total detected light intensity to the reference light intensity, has low requirements for the stability of the illumination beam, and the same substrate can generate the same interference contrast image on different devices;

[0040] Thirdly, the device required by the present invention has a simple structure, does not require special optical elements, and can use a self - built optical microscope or be directly modified from a commercial microscope;

[0041] Fourthly, the present invention has no limitation on the illumination light wavelength, and monochromatic light or a mixture of monochromatic lights with wavelengths in the range of 10 nm to 300 μm can be selected according to requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The systems and methods of the present invention will be further specifically described below in conjunction with the drawings and specific embodiments.

[0043] Figure 1A It is a schematic diagram of the present invention based on reflection - type interference scattering microscopy. Figure 1BIt is the schematic diagram of the present invention based on transmission interferometric scattering microscopy.

[0044] Figure 2A It is a specific implementation manner of the present invention based on reflection interferometric scattering microscopy. Figure 2B It is a specific implementation manner of the present invention based on reflection interferometric scattering microscopy and adding a spatial filter.

[0045] Figure 3A It is a specific implementation manner of the present invention based on transmission interferometric scattering microscopy. Figure 3B It is a specific implementation manner of the present invention based on transmission interferometric scattering microscopy and adding a spatial filter.

[0046] Figure 4A It is based on the present invention Figure 2A The interference contrast image measured for a region of the glass slide in the specific implementation manner shown. Figure 4B It is based on the present invention Figure 2A In the specific implementation manner shown, the glass slide is taken away from the displacement adjustment device and then put back into the displacement adjustment device, and the interference contrast image measured for the same region. Figure 4C It is Figure 4A and Figure 4B The cross-correlation function distribution. Figure 4D It shows Figure 2A Using the device shown, after 100 measurements, the error between the displacement of the glass slide and the true displacement.

[0047] Figure 5A It is based on the present invention Figure 2B The interference contrast image measured for a region of the glass slide in the specific implementation manner shown. Figure 5B It is based on the present invention Figure 2B In the specific implementation manner shown, the glass slide is taken away from the displacement adjustment device and then put back into the displacement adjustment device, and the interference contrast image measured for the same region. Figure 5C It is Figure 5A and Figure 5B The cross-correlation function distribution. Figure 5D It shows Figure 2B Using the device shown, after 100 measurements, the error between the displacement of the glass slide and the true displacement.

[0048] It should be noted that the dimensions in the reference drawings and the actual dimensions used do not form a proportional relationship. Specific implementation manner

[0049] To better understand the substrate lateral displacement monitoring and lateral alignment system and method disclosed in the present invention, the following describes specific embodiments of the present invention with reference to the accompanying drawings by way of non-limiting examples. It should be noted that those skilled in the art should understand that reasonable modifications to the system and method of the present invention still fall within the protection scope of the present invention.

[0050] What the present invention discloses is a substrate lateral displacement monitoring and lateral alignment system and method. The substrate lateral displacement monitoring and lateral alignment system includes a light source assembly, a microscopic system, a detector, a displacement adjustment device, and a computer processing device. In addition, a spatial filter can be optionally added to the microscopic system.

[0051] Figure 1A and Figure 1B respectively show two implementation principles of the system and method of the present invention.

[0052] The light source assembly, which is configured to provide an illumination beam. As Figure 1A 、 1B shown, the light source assembly 101 generates an illumination beam 102, and under the guidance of the microscopic system 103, the illumination beam 102 irradiates the surface of the substrate.

[0053] The substrate 104 can be any substrate, including but not limited to glass products, mica, silicon wafers, organic materials, metal products, etc. As Figure 1A and Figure 1B shown, the substrate 104 has surface undulations at the nanometer or sub-nanometer level. Part of the illumination beam 102 will be scattered by the undulations on the surface of the substrate 104, particles or structures on the surface of the substrate 104 to form a scattered beam 107. According to the properties of the substrate 104 and actual needs, the displacement adjustment device 105 can move the substrate 104 so that the microscopic system can image the upper surface or the lower surface of the substrate 104.

[0054] The microscopic system can directly use a commercial microscope or a self-built microscope. As Figure 1A shown, the microscopic system 103 can be arranged as a reflective type according to the properties of the substrate 104 and actual usage needs, that is, the illumination beam irradiates the surface of the substrate 104, and part of the illumination light is reflected by the surface of the substrate 104 to form the reference beam 106 in the detection beam; as Figure 1B shown, according to the properties of the substrate 104 and actual usage needs, the microscopic system 103 can also be arranged as a transmissive type, that is, the illumination light irradiates the surface of the substrate 104, and part of the illumination light transmits through the substrate 104 to form the reference beam 106 in the detection beam.

[0055] As Figure 1A and Figure 1BAs shown, the detector 108 is used to receive a detection light beam, which includes a reference light beam 106 and a scattered light beam 107, and generate an optical image.

[0056] As Figure 1A and Figure 1B shown, the displacement adjustment device 105 is used to carry the substrate 104 and can move the substrate 104 as needed.

[0057] A computer processing device is used to process the optical image, generate an interference contrast image containing a large number of speckles, extract displacement information according to the interference contrast image, and control the displacement adjustment device 105 to move the substrate 104. The specific steps for realizing the lateral displacement monitoring and lateral alignment of the substrate are as follows:

[0058] 1. Collect the optical image of the surface area S of the substrate and record it as I. Take the average of each pixel of the optical images of multiple areas and record it as I average ;

[0059] 2. Perform the operation C=(I1 - I average ) - 1 to obtain the interference contrast image of the area S;

[0060] 3. Perform a cross - correlation function analysis on the interference contrast image C(t1) obtained at time t1 and the contrast image C(t2) obtained at time t2, that is, XC = ∫∫C(t1,x,y)C(t2,x + Δx,y + Δy)dxdy;

[0061] 4. Fit the center position (Δx0,Δy0) of the cross - correlation function XC, and the displacement of the substrate at time t2 relative to that at time t1 can be monitored as (-Δx0,-Δy0), realizing the lateral displacement monitoring of the substrate;

[0062] 5. Further, according to the monitored displacement information, move the substrate to a specified position, for example, move the substrate to the position it was at time t1.

[0063] Figure 2A It is a specific implementation manner of realizing the present invention by arranging the microscopic system as a reflective illumination. In Figure 2AIn it, the microscopic system consists of a lens 201, a beam splitter 202, an objective lens 203, and a lens 204. Among them, the beam splitter 202 is located at the rear focal plane of the objective lens 203. The substrate 104 is placed on the displacement adjustment device 105. The displacement adjustment device 105 is controlled by the computer system and can move the substrate 104 to a specified position. The light source assembly 101 emits an illumination beam 102, which is focused by the lens 201 on the rear focal plane of the objective lens 203, reflected by the beam splitter 202 and enters the objective lens 203, irradiating the substrate 104 to form illumination. A part of the illumination beam 102 is directly reflected by the substrate 104 to form a reference beam 106. At the same time, a part of it is scattered by the nanoscale or sub-nanoscale undulations on the surface of the substrate 104, particles or structures on the surface of the substrate 104 to form a scattered beam 107. The reference beam 106 and the scattered beam 107 together form a detection beam, which is collected by the objective lens 203, passes through the beam splitter 202, and finally is focused by the lens 204 on the detector 108 to form an optical image. As described above, the computer system processes the optical image read from the detector 108 into an interference contrast image, and monitors the displacement of the substrate 104 according to the aforementioned method from the interference contrast images at different times. Further, according to the monitored displacement information, the displacement adjustment device 105 is controlled to move the substrate 104 to a specified position for alignment.

[0064] Figure 2B One specific implementation of the present invention is to arrange the microscopic system for reflective illumination and add a spatial filter in the microscopic system. Compared with Figure 2A the embodiment shown, Figure 2B a spatial filter 205 is additionally added in the microscopic system. As Figure 2B shown, at the rear focal plane of the objective lens 203, the reference beam 106 is a focused beam, and the scattered beam 107 is a parallel beam filling the rear focal plane. The size of the spatial filter 205 is larger than the spot size of the reference beam 106 and smaller than the spot size of the scattered beam 107. The spatial filter 205 will attenuate the intensity of the reference beam 106 and not attenuate the intensity of the scattered beam 107, improving the interference contrast and making the accuracy of the lateral displacement monitoring and lateral alignment of the substrate higher.

[0065] Figure 3A One specific implementation of the present invention is to arrange the microscopic system for transmissive illumination. In Figure 3A it, the microscopic system consists of a lens 201, an objective lens 203, a lens 204, and a lens 301. Compared with Figure 2A the embodiment shown, Figure 3AIn the illustrated embodiment, the illumination system and the detection system are on different sides of the sample. The light source assembly 101, the lens 201, and the lens 301 form the illumination system. The objective lens 203, the lens 204, and the detector 108 form the detection system. Since the illumination system and the detection system do not share an optical path, there is no need to use a beam splitter. The illumination beam 102 is guided by the lens 201 and the lens 301 to the substrate 104 to form illumination. Figure 3A In the illustrated embodiment, other configurations may be the same as Figure 2A the illustrated embodiment.

[0066] Figure 3B This is a specific implementation manner of arranging the microscopic system into transmitted illumination and adding a spatial filter in the microscopic system to implement the present invention. Compared with Figure 3A the illustrated embodiment, Figure 3B a spatial filter 205 is additionally added in the microscopic system. In Figure 3B the illustrated embodiment, the setting and function of the spatial filter 205 may be the same as Figure 2B the illustrated embodiment.

[0067] Figure 4A This is Figure 2A the interference contrast image measured for a region of the glass slide using the configuration shown. It can be seen that the height fluctuations of the glass slide surface at the nanometer or sub-nanometer level result in a large number of light and dark speckles. The speckle shapes in each region have no similarity, demonstrating the specificity of the speckles in each region. Figure 4B This is the interference contrast image measured for the same region after removing the glass slide from the displacement adjustment device 105 and then putting the glass slide back into the displacement adjustment device 105. It can be seen that Figure 4A compared with Figure 4B it is almost indistinguishable, proving that the speckles caused by the surface fluctuations of the glass slide have good repeatability. Due to the specificity and repeatability of the speckles in each region, the movement of the speckles can be used to characterize the movement of the glass slide. Figure 4C This is Figure 4A and Figure 4B the cross-correlation function distribution. The black cross represents the center of the cross-correlation function. It can be obtained that compared with when measuring Figure 4A at the time of measurement Figure 4B the glass slide has been translated 100 nm in the x direction and 50 nm in the y direction. Figure 4D This shows Figure 2A the error between the glass slide displacement and the true displacement obtained from 100 measurements using the device shown. It can be seen from this that the standard deviation of these 100 groups of errors is 0.8 nm. Therefore, by using the system and method disclosed in the present invention, sub-nanometer-level precision lateral alignment of the substrate can be achieved.

[0068] Figure 5A This is Figure 2BThe interference contrast image of a region of the glass slide shown, from which it can be seen that the undulations with a height of nanometers or sub-nanometers on the surface of the glass slide cause a large number of light and dark speckles. Figure 5A Compared with Figure 4A , it can be seen that Figure 2B The spatial filter 205 added in Figure 5B greatly improves the interference contrast of the speckles. Figure 5C is Figure 5A and Figure 5B The cross-correlation function distribution. The black cross represents the center of the cross-correlation function. Since the glass slide has been moved back to the position at the first measurement during the second measurement, the center of the cross-correlation function is at (0nm, 0nm). Figure 5D shows Figure 2B The error between the displacement of the glass slide and the true displacement obtained by performing 100 measurements using the device shown. It can be seen from this that the standard deviation of these 100 groups of errors is 0.4nm. Therefore, adding a spatial filter to the system disclosed in the present invention to attenuate the intensity of the reference light and improve the interference contrast helps to achieve higher-precision substrate lateral displacement monitoring and lateral alignment accuracy.

Claims

1. A substrate lateral displacement monitoring and lateral alignment system, characterized in that, Comprising: A light source assembly for providing an illumination beam; A microscopic system for guiding the illumination beam to form a detection beam and guiding the detection beam to a detector; the detection beam includes a reference beam directly reflected or transmitted by the substrate, and also includes a scattered beam generated by nano-scale or sub-nano-scale undulations on the substrate surface, particles or structures on the substrate surface; A detector for generating an optical image; A displacement adjustment device for carrying the substrate and adjusting the position of the substrate; A computer processing system for processing the optical image, generating an interference contrast image, extracting the position information of the substrate, and controlling the displacement adjustment device.

2. The substrate lateral displacement monitoring and lateral alignment system according to claim 1, characterized in that, The microscopic system includes a spatial filter.

3. The substrate lateral displacement monitoring and lateral alignment system according to claim 1, characterized in that, Processing the optical image and generating an interference image means processing the optical image into an interference contrast image formed by the interference of the reference beam and the scattered beam.

4. The substrate lateral displacement monitoring and lateral alignment system according to claim 1, characterized in that, Extracting the position information of the substrate means performing a cross-correlation function analysis on the interference contrast images at different times, fitting the center position of the cross-correlation function, and extracting the position of the substrate at different times.

5. The substrate lateral displacement monitoring and lateral alignment system according to claim 4, characterized in that The computer processing system is further configured to monitor the lateral displacement of the substrate at each moment according to the position of the substrate at each moment.

6. The substrate lateral displacement monitoring and lateral alignment system according to claim 5, characterized in that The computer processing system is further configured to control the displacement adjustment device according to the lateral displacement of the substrate and move the substrate to a specified position for alignment.

7. A method for monitoring the lateral displacement and lateral alignment of a substrate, characterized in that, Including the following steps: The light source assembly emits an illumination beam; Guiding the illumination beam to the substrate surface through the microscopic system to form a detection beam and guiding the detection beam to the detector to form an optical image; Processing the optical image into an interference contrast image formed by the interference of the reference beam and the scattered beam; the detection beam includes a reference beam directly reflected or transmitted by the substrate, and also includes a scattered beam generated by nano-scale or sub-nano-scale undulations on the substrate surface, particles or structures on the substrate surface; Performing a cross-correlation function analysis on the interference contrast images at different times, fitting the center position of the cross-correlation function, and extracting the position information of the substrate at different times; Monitoring the lateral displacement of the substrate according to the position information of the substrate at different times; Controlling the displacement adjustment device according to the monitored lateral displacement and moving the substrate to a specified position.

8. The substrate lateral displacement monitoring and lateral alignment method according to claim 7, wherein Performing spatial filtering in the microscopic system.

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