Photoresist thickness detection system and method

Abstract

The present application provides a photoresist thickness detection system and method, the system comprises: a stripe display module, a substrate; when the substrate is made of a light-transmitting material, the stripe display module is attached to the upper surface of the substrate, the lower surface of the substrate is coated with photoresist, a standard plane mirror is arranged below the photoresist, and the center of the stripe display module is offset from the optical axis of the system; the light emitted by the stripes in the stripe display module is reflected to the image collector by the standard plane mirror after transmitting through the substrate and the photoresist; when the substrate is made of a non-light-transmitting material, the upper surface of the substrate is coated with photoresist, and the substrate is arranged below the stripe display module; the center of the stripe display module is offset from the optical axis of the substrate; the light emitted by the stripes in the stripe display module is refracted to the image collector again after transmitting through the photoresist, reflecting through the substrate and transmitting through the photoresist again. The present application can realize the measurement of the photoresist thickness and the rapid evaluation of the uniformity of the photoresist thickness.

Description

Technical Field

[0001] This invention belongs to the field of photoresist thickness measurement technology, and particularly relates to a photoresist thickness detection system and method. Background Technology

[0002] Photoresist is a core functional material in the modern electronics and information industry. It achieves pattern transfer through photolithography and is widely used in semiconductor chips, advanced packaging, printed circuit boards, and microelectromechanical systems (MEMS). It is crucial for realizing intricate structures such as nanoscale circuits, microvia interconnects, and high-density wiring, ensuring the final performance, integration, and reliability of electronic devices. In this process, the thickness and uniformity of the photoresist are key parameters determining the performance of the final product: the thickness directly affects the resolution of the photolithography process, the penetration and dissolution efficiency of the developer, the thermal stability of the material, and production costs. If the photoresist layer is too thick, it can easily lead to blurred edges after exposure, incomplete development, pattern distortion, and material waste; conversely, if the photoresist layer is too thin, it may cause pattern defects, over-etching, or even substrate damage. Furthermore, poor thickness uniformity will result in uneven distribution of exposure energy, leading to inconsistent structural morphology of microelectronic components, ultimately impairing the performance and reliability of the devices. Therefore, accurate measurement of photoresist thickness is an indispensable step in improving the quality of component fabrication, and the measurement results have direct guiding significance for optimizing the fabrication process.

[0003] Currently, common methods for film thickness measurement mainly include expert judgment, scanning electron microscopy (SEM), interferometry, spectral scanning, and elliptic polarization. Experts determine film thickness based on experience, typically estimating it using spin coating speed-film thickness data provided by the supplier combined with their personal experience. This method is highly subjective and has poor repeatability. SEM requires measurement of the sample cross-section, making it a destructive test; sample preparation is complex and it cannot be used for online testing. Interferometry uses equal-thickness interference fringes for thickness measurement, achieving non-contact measurement, but the equipment is expensive and requires extremely stable environmental conditions. Spectral scanning analyzes the absorption or reflection spectrum of light to invert film thickness, offering high accuracy; however, the equipment is expensive and the operation is complex. Elliptic polarization extracts film thickness and optical constants by detecting changes in the polarization state between incident and reflected light, achieving nanometer-level accuracy. However, its results are affected by various factors such as incident angle accuracy and polarizer calibration errors, making system calibration complex and measurement stability difficult to guarantee.

[0004] At the patent technology level, various optical measurement schemes have been proposed, but each still has its limitations. Invention patent number CN202210707177.X provides a mask photoresist thickness measurement scheme based on the interference principle. Its advantage lies in inverting the thickness by analyzing the interference effect between the surface and the substrate reflected light, making it particularly suitable for detecting thinner photoresist layers, thus improving measurement accuracy and sensitivity. However, the measurement accuracy of this method is highly susceptible to environmental vibration interference, and obtaining stable interference requires extremely stringent requirements on sample surface quality and system stability. Invention patent number CN202411972001.2 relates to a film thickness measurement method based on a spectrometer. Its advantage lies in its ability to handle multilayer film structures and achieve high measurement accuracy by constructing complex film system models and performing iterative optimization. However, this method involves a complex modeling process, a large computational load, and high requirements for system hardware and algorithm processing capabilities. In addition, invention patent number TW112140752 relates to a thin film thickness measurement device including a spectral ellipsometer. Its advantage is that by using multi-wavelength polarized light detection, it can simultaneously obtain the thickness and optical constants of the thin film, providing rich measurement information and extremely high accuracy. However, ellipsometer technology is easily affected by various factors such as incident angle and polarizer calibration error, making system calibration cumbersome and posing a significant challenge to measurement stability.

[0005] In summary, the aforementioned quantitative and non-destructive detection methods have inherent drawbacks such as expensive instruments, cumbersome operation, and susceptibility to environmental interference. Therefore, this invention proposes a photoresist thickness detection system and method based on stripe deflection. Summary of the Invention

[0006] The purpose of this invention is to provide a photoresist thickness detection system and method, which has the advantages of simple structure, low cost, and convenient operation. It is a non-contact, quantitative, and non-destructive optical measurement method. A red sine stripe pattern is displayed on an LCD screen. A camera acquires red sine stripe patterns transmitted or reflected from the substrate in two cases: with and without photoresist. The corresponding phase points of the acquired and designed red sine stripe patterns are determined. Combined with the principle of ray tracing, the thickness value of the photoresist at any location is calculated, thereby achieving rapid, full-field evaluation of the photoresist thickness uniformity. The technical solution adopted is as follows: A photoresist thickness detection system, comprising: Stripe display module 1 is used to display vertical sine stripe patterns and horizontal sine stripe patterns; Substrate 2, parallel to stripe display module 1, is made of light-transmitting material or non-light-transmitting material; When the substrate 2 is made of a light-transmitting material, the stripe display module 1 is attached to the upper surface of the substrate 2, and the lower surface of the substrate 2 is coated with photoresist 3. A standard plane mirror 4 parallel to the stripe display module 1 is provided below the photoresist 3, and the center of the stripe display module 1 is offset from the optical axis of the system. The light emitted from the stripes in the stripe display module 1 passes through the substrate 2 and the photoresist 3 and is reflected by the standard plane mirror 4 to the image acquisition device 6, where it is acquired. When the substrate 2 is made of a non-transparent material, the upper surface of the substrate 2 is coated with photoresist 3, and the substrate 2 is located below the stripe display module 1; the center of the stripe display module 1 is offset from the optical axis of the system; the light emitted from the stripes in the stripe display module 1 passes through the photoresist 3, is reflected by the substrate 2 and passes through the photoresist 3 again, and is refracted by the photoresist 3 to the image acquisition device 6, where it is acquired by the image acquisition device 6. The system optical axis is the world coordinate system. of axis; And control module 7, which connects image acquisition unit 6 and stripe display module 1.

[0007] Preferably, the image acquisition device 6 is a pinhole camera.

[0008] Preferably, it further includes a storage device 9, a power supply 8, a display device 11, and a human-computer interaction module 10 connected to the control module 7.

[0009] Preferably, the stripe display module 1 is a liquid crystal display screen.

[0010] Preferably, the control module 7 is a CPU.

[0011] A method for detecting photoresist thickness, based on the aforementioned photoresist thickness detection system, includes the following steps when the substrate 2 is made of a light-transmitting material: Step 1: Obtain the camera's focal length and obtain the camera coordinate system. and world coordinate system The conversion relationship between them; Step 2: Find any light source point Collect the corresponding phase points, i.e., pixels, on the stripe pattern. : Step 2A: Design horizontal sinusoidal fringes, and use phase shifting technology and spatial phase unfolding algorithm to obtain the absolute phase distribution of the horizontally acquired fringe pattern; Step 2B: Design vertical sinusoidal fringes, and use phase shifting technology and spatial phase unfolding algorithm to obtain the absolute phase distribution of the vertically acquired fringe pattern; Step 2C: Compare the phase distribution of the horizontal sinusoidal fringe pattern and the horizontally acquired fringe pattern to obtain the light source point. Identify the corresponding phase points on the horizontally acquired fringe pattern; compare the phase distribution of the vertical sine fringe pattern and the vertically acquired fringe pattern to obtain the light source points. Phase points of the same name on the vertically acquired stripe pattern; Among them, two phase points with the same name are identical, i.e., pixel points. ; Step 3: Obtain pixels Based on the transformation relationship obtained in step 1, the coordinates W0 in the camera coordinate system are transformed into world coordinates W1. Specifically, based on the horizontally acquired stripe pattern, a coordinate value of coordinate W0 is obtained. Based on the vertically acquired stripe pattern, obtain another coordinate value for coordinate W0. Coordinate W0 = ( ， , ); -focal length; Step 4, point World coordinates W3 determined: Based on pixels World coordinates W1, pinhole location of image acquisition device 6 World coordinates W2 determine a straight line ,straight line The intersection point with the standard plane mirror 4 is point 1. ; Acquisition Points World coordinates W3; Step 5, Light Normal to photoresist 3 The included angle Sure: straight line The angle between the ray and the normal of the standard plane mirror 4 is the angle of the ray. With normal The included angle ; Step 6, Point and points Determining the distance between them: Light The intersection of the extension of the line and the lower surface of substrate 2 is denoted as point . ; light The intersection point with the lower surface of substrate 2 is denoted as point . ; Finding pixels when photoresist 3 is not placed The corresponding phase points on the design stripe diagram, i.e., the light source points. ; Refracted light The corresponding incident ray is the light ray. light Intersecting with stripe display module 1 at E; According to the law of refraction, ray tracing is performed. Parallel to light Therefore, point and points Distance between points and points The distances between them are equal, that is ; Light source point World coordinates are designated W4 = ( , , ), light source point World coordinates are marked W5 = ( , , ); ; Step 7: Calculate the photoresist thickness: Refractive index of photoresist 3 Given that point and points Distance between Light With normal The included angle and photoresist refractive index Input the thickness model from control module 7 to obtain the photoresist thickness.

[0012] Preferably, the thickness model is: ; in, - The thickness of the photoresist; -light With normal The included angle; - The refractive index of photoresist 3.

[0013] A method for detecting photoresist thickness, based on the aforementioned photoresist thickness detection system, includes the following steps when the substrate 2 is made of a non-transparent material: Step 1: Obtain the camera's focal length and obtain the camera coordinate system. and world coordinate system The relationship between them; Step 2: Find any light source point Collect the corresponding phase points, i.e., pixels, on the stripe pattern. : Step 2A: Design horizontal sinusoidal fringes, and use phase shifting technology and spatial phase unfolding algorithm to obtain the absolute phase distribution of the horizontally acquired fringe pattern; Step 2B: Design vertical sinusoidal fringes, and use phase shifting technology and spatial phase unfolding algorithm to obtain the absolute phase distribution of the vertically acquired fringe pattern; Step 2C: Compare the phase distribution of the horizontal sinusoidal fringe pattern and the horizontally acquired fringe pattern to obtain the light source point. Identify the corresponding phase points on the horizontally acquired fringe pattern; compare the phase distribution of the vertical sine fringe pattern and the vertically acquired fringe pattern to obtain the light source points. Phase points of the same name on the vertically acquired stripe pattern; Among them, two phase points with the same name are identical, i.e., pixel points. ; Step 3: Obtain pixels The coordinates W0 in the camera coordinate system are converted to world coordinates W1 based on the transformation relationship obtained in step 1. Specifically, based on the horizontally acquired stripe pattern, a coordinate value of coordinate W0 is obtained. Based on the vertically acquired stripe pattern, obtain another coordinate value for coordinate W0. Coordinate W0 = ( ， , ); -focal length; Step 4, point World coordinates W3 determined: Based on pixels World coordinates W1, pinhole location of image acquisition device 6 World coordinates W2 determine a straight line The intersection of the straight line and substrate 2 is point 2. ; Acquisition Points World coordinates W3; Step 5, point World coordinates W4 determined: Finding pixels when photoresist 3 is not placed The corresponding phase points on the design stripe diagram, i.e., the light source points. ,point The world coordinates are marked as W4; Step 6: Calculate the photoresist thickness: Point World coordinates W4, point World coordinates W3, point World coordinates W1, point World coordinates W2, distance from substrate 2 to stripe display module 1 Input the thickness model from control module 7 to obtain the photoresist thickness.

[0014] Preferably, the thickness model is: ; in, - The thickness of the photoresist; -point of Axis coordinate values; -point of Axis coordinate values; -point of Axis coordinate values; -point of Axis coordinate values; -point of Axis coordinate values; -point of Axis coordinate values; - The distance between the stripe display module 1 and the substrate 2.

[0015] Compared with the prior art, the advantages of the present invention are: 1. Innovative optical path and information carrier: A liquid crystal display screen is used to show specific patterns as the structured light source, replacing the laser source in traditional interferometers or the broadband source in spectrometers. This design not only reduces cost and system complexity, but also encodes thickness information into the phase distribution of the fringes. The thickness is obtained by calculating the phase change rather than directly measuring the light intensity or color, resulting in stronger anti-interference capabilities.

[0016] 2. Robust Algorithm Core: By identifying the corresponding phase points of the acquired image and the original sinusoidal fringe image, and combining this with ray tracing to calculate the thickness, this method establishes a precise and stable mathematical conversion model from image information to physical thickness. This avoids the cumulative errors introduced by the complexity of the model and the large number of parameters in techniques such as elliptic polarization.

[0017] 3. Practical Design for Industrial Applications: The entire system has a simple structure, with key components such as the LCD screen and camera being mature industrial products, resulting in low cost, high reliability, and ease of maintenance and integration. This directly addresses the two major bottlenecks mentioned in the background technology: "expensive instruments" and "complex operation." The high-precision thickness detection achieved by this solution can meet the online monitoring needs of wet film coating and is also suitable for quality control in dry film production, laying a solid foundation for large-scale application in industries such as PCB. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the photoresist thickness detection system in Example 1; Figure 2 This is a schematic diagram of the control component structure; Figure 3 A schematic diagram of a vertical sine fringe pattern; Figure 4 This is a schematic diagram of a horizontal sine fringe pattern; Figure 5 This is a schematic diagram illustrating the photoresist thickness detection principle in Example 1; Figure 6 This is a schematic diagram of the photoresist thickness detection system in Example 2; Figure 7 This is a schematic diagram illustrating the photoresist thickness detection principle in Example 2. Figure 8 This is a schematic diagram of the world coordinates of the center of the liquid crystal display screen in Example 2.

[0019] 1-Striped display module, 2-Substrate, 3-Photoresist, 4-Standard plane mirror, 5-Control component, 6-Image acquisition unit, 7-Control module, 8-Power supply, 9-Storage device, 10-Human-machine interaction module, 11-Display device. Detailed Implementation

[0020] The photoresist thickness detection system and method of the present invention will now be described in more detail with reference to the schematic diagrams, which illustrate preferred embodiments of the invention. It should be understood that those skilled in the art can modify the invention described herein while still achieving its advantageous effects. Therefore, the following description should be understood as being of general knowledge to those skilled in the art and is not intended to limit the invention.

[0021] Example 1 The substrate 2 is made of a light-transmitting material, such as glass, quartz, or polyethylene terephthalate (PET).

[0022] Thickness of substrate 2 and refractive index n 1. Known.

[0023] like Figures 1-5A photoresist thickness detection system includes: a stripe display module 1, a substrate 2, photoresist 3, a standard plane mirror 4, a control module 7, and an image acquisition device 6.

[0024] Stripe display module 1, used to display stripes such as Figure 3 The vertical red sine stripe pattern shown and as follows Figure 4 The horizontal red sine stripe pattern shown; Stripe display module 1 is an LCD screen.

[0025] The substrate 2 is parallel to the stripe display module 1; the substrate 2 is disposed between the stripe display module 1 and the standard plane mirror 4.

[0026] The striped display module 1 is attached to the upper surface of the substrate 2, the lower surface of the substrate 2 is coated with photoresist 3, and a standard plane mirror 4 parallel to the striped display module 1 is provided below the photoresist 3. The center of the striped display module 1 is offset from the optical axis of the system.

[0027] System optical axis This is the central axis of the standard plane mirror 4.

[0028] The light emitted from the stripes in the stripe display module 1 passes through the substrate 2 and photoresist 3 and is reflected by the standard plane mirror 4 to the image acquisition device 6, where it is collected by the image acquisition device 6. Wherein, the optical axis is the world coordinate system. of axis; The control module 7 is connected to the image acquisition unit 6 and the stripe display module 1.

[0029] In this embodiment, the image acquisition device 6 is a pinhole camera.

[0030] The control module 7 is connected to the storage device 9, the power supply 8, the display device 11, and the human-computer interaction module 10. The control module 7 is the CPU.

[0031] like Figure 2 As shown, the control component 5 includes an image acquisition device 6, a control module 7, a storage device 9, a power supply 8, a display device 11, and a human-computer interaction module 10.

[0032] In this embodiment, the number of stripes is input through the human-computer interaction module 10, and the control module 7 assigns the generated sinusoidal stripe intensity value to the red of the three primary colors of the stripe display module 1, while keeping the values ​​of the green and blue channels at 0.

[0033] like Figure 3 As shown, a stripe is defined as the distance from the center of a black area to the adjacent center of a black area, or as the distance from the center of a red area to the adjacent center of a red area. Figure 3 There are a total of 8 stripes in the middle.

[0034] Image acquisition device 6 acquires and stores the stripe pattern in storage device 9 and control module 7. Control module 7 analyzes the image information and calculates the thickness. Display device 11 displays the image structure.

[0035] A method for measuring photoresist thickness includes the following steps: Step 1: Using Zhang Zhengyou's camera calibration method, calibrate the camera's intrinsic and extrinsic parameters to obtain the camera's focal length. f Camera coordinate system and world coordinate system Relationship .

[0036] ; in, 3 3 matrices, representing the world coordinate system Rotation vector during coordinate axis transformation in the axial camera coordinate system; It is a translation vector; This indicates that the value at that position in the matrix is ​​zero.

[0037] Step 2: Determine any light source point Collect the corresponding phase points, i.e., pixels, on the stripe pattern. .

[0038] Step 2A: Design horizontal red sinusoidal stripes, and use three-step phase shifting technology and spatial phase unfolding technology to obtain the absolute phase distribution of the horizontally acquired stripe pattern.

[0039] like Figure 4 As shown, in order for the stripe display module 1 to generate a horizontal red sine stripe pattern, the operations involved by existing technology are as follows: Using the center of the LCD screen as the origin, the display screen is gridded, and a coordinate system for the LCD screen is established. and the display screen is in a vertical direction (i.e. The position value in the axial direction is converted into a phase value, and then the intensity value of the horizontal sinusoidal stripe is obtained.

[0040] Assign the intensity value of the horizontal sine stripe to the red channel in the RGB color mode, while keeping the values ​​of the green and blue channels at 0.

[0041] Stripe display module 1 displays a horizontal red sine stripe pattern.

[0042] Figure 4 middle: Red sine stripes along The axes are evenly distributed and spaced apart.

[0043] Figure 5 In the middle, along ozThe effect observed when viewing the stripe display module 1 from the negative axis is as follows: Figure 4 As shown.

[0044] Using a three-step phase-shifting technique, image acquisition device 6 acquired three horizontal stripe patterns.

[0045] Based on three horizontally acquired fringe patterns, the control module 7 calculates the truncated phase of the horizontally acquired fringe patterns and obtains the absolute phase distribution of the horizontally acquired fringe patterns using the spatial phase unfolding method.

[0046] Step 2B: Design vertical red sinusoidal stripes and use the three-step phase shift technique to obtain the absolute phase distribution of the vertically acquired stripe pattern; like Figure 3 As shown, the operations involved in making the stripe display module 1 display a vertical red sine stripe pattern are as follows: Using the center of the LCD screen as the origin, the screen is gridded and a planar coordinate system is established. and the display screen is oriented horizontally (i.e. The position value in the axial direction is converted into a phase value, and then the intensity value of the vertical sine stripe is obtained.

[0047] Assign the intensity value of the vertical sine stripe to the red channel in the RGB color mode, while keeping the values ​​of the green and blue channels at 0.

[0048] Stripe display module 1 displays a vertical red sine stripe pattern.

[0049] Figure 3 middle: Red sine stripes along The axes are evenly distributed and spaced apart.

[0050] Figure 5 In the middle, along The effect observed when viewing the stripe display module 1 from the negative axis is as follows: Figure 3 As shown.

[0051] Using a three-step phase-shifting technique, image acquisition device 6 acquired three vertically acquired stripe patterns.

[0052] Based on three vertically acquired fringe patterns, the control module 7 calculates the truncated phase of the vertically acquired fringe patterns and obtains the absolute phase distribution of the vertically acquired fringe patterns using the spatial phase unfolding method.

[0053] Step 2C: Control module 7 compares the absolute phase distribution of the horizontal red sine stripe pattern and the horizontal acquisition stripe pattern, and obtains the light source point using the phase value matching method. The control module 7 compares the absolute phase distribution of the vertical red sine stripe pattern and the vertically acquired stripe pattern to obtain the light source points. Phase points of the same name on the vertically acquired stripe pattern; Among them, two phase points with the same name are identical, i.e., pixel points. .

[0054] Step 3: Obtain pixels Based on the transformation relationship obtained in step 1, the coordinates W0 in the camera coordinate system are transformed into world coordinates W1. Specifically, based on the horizontally acquired stripe pattern, a coordinate value of coordinate W0 is obtained. ; Based on the vertically acquired stripe pattern, obtain another coordinate value for coordinate W0. ; Coordinate W0 = ( ， , ); The image plane of the camera is in the camera coordinate system Within the plane.

[0055] The camera coordinate system and world coordinate system were obtained using Zhang Zhengyou's camera calibration method. The conversion relationship between them is then used to calculate the pixel points. The coordinates W1 in the world coordinate system are ( , , Camera pinhole location Let the origin of the camera coordinate system be (0, 0, 0). Based on the transformation relationship obtained in step 1, convert it to coordinates W2= in the world coordinate system. , , ).

[0056] Step 4: Determine the location of point M: Based on pixels World coordinates W1, camera pinhole location of image acquisition device 6 World coordinates W2 determine a straight line The intersection of the straight line and the standard plane mirror 4 is point 4. .

[0057] Calculate a line using the geometric relationship between a line and a surface. Intersection with standard plane mirror 4 Obtain the world coordinates W3 of point M. , , The specific calculation process is as follows: straight line The equation is: ; Standard plane mirror 4 is:

[0058] Will Substitute the line The equation yields, ; ; ; Step 5, Light With normal The included angle Sure: According to the law of reflection, the normal of photoresist 3 The normals of both the standard plane mirror 4 and the normals are parallel to each other. Axis, line The angle between the ray and the normal of a standard plane mirror is the angle of the ray. With normal The included angle .

[0059] Step 6, Point and points Determining the distance between them: The distance from the standard plane mirror 4 to the stripe display module 1 was measured using a laser rangefinder. The thickness of substrate 2 Known.

[0060] Light The intersection of the extension of the line and the lower surface of substrate 2 is denoted as point . light The intersection point with the lower surface of substrate 2 is denoted as point . .

[0061] Calculation points and points Distance between them in the world coordinate system Specific steps: When the photoresist 3 is not placed, the method in step 2 is used to find the corresponding phase point of pixel T on the stripe pattern and on the designed stripe pattern (the vertical sine stripe pattern and the horizontal sine stripe pattern displayed by the stripe display module 1), that is, the light source point E, and the coordinate position of point E in the coordinate system of the liquid crystal display screen ( ).

[0062] like Figure 5 As shown: (1) When placing photoresist 3: Incident light Light is formed after refraction through the lower surface of substrate 2. ; Light Light is formed after being refracted by the lower surface of photoresist 3. .

[0063] in, For light The angle between the normal to substrate 2 and the normal to substrate 2.

[0064] (2) When photoresist 3 is not placed: Incident light Light is formed after refraction through the lower surface of substrate 2. .

[0065] When photoresist 3 is not placed, the light source point World coordinates are designated W4 = ( , , ).

[0066] In the coordinate system of the LCD screen, the light source point The location is displayed on a gridded screen with coordinate values. ); In the world coordinate system, the light source point W5 = ( , , ).

[0067] Because the LCD screen is located in the world coordinate system = Therefore, point is in the plane. and points The distance between them is equal in both coordinate systems (world coordinate system and LCD screen coordinate system).

[0068] Therefore, the coordinate system of the liquid crystal display screen can be solved. Length is sufficient.

[0069] Refracted light The corresponding incident ray is , Intersecting with stripe display module 1 .

[0070] According to the law of refraction, ray tracing is performed. Parallel to light Therefore, point and points Distance between points and points The distances between them are equal, that is .

[0071] In the coordinate system of the LCD screen, the light source point and light source point The distance between them is, ; Figure 5 middle, < The reason is that the refractive index of substrate 2 is greater than that of photoresist 3. According to the law of reflection, sin = sin A higher refractive index results in a smaller angle.

[0072] Light Parallel to light Reason: and points The included angle between the normals is , and points The included angle of the normal is also Using the law of refraction, sin = sin The formula has been derived earlier.

[0073] When photoresist is absent, and points The included angle of the normal is also , Then the corresponding point The angle of incidence is definitely 1. Therefore, light Parallel to light .

[0074] When photoresist 3 is not placed, use the method in step 2 to locate and collect pixels on the stripe pattern. The specific steps for finding the corresponding phase point, i.e., the light source point E, include: The LCD screen displays the horizontal and vertical red sine bars designed in step 2. Using a three-step phase-shift technique, image acquisition unit 6 acquires three horizontal and three vertical fringe patterns. Control module 7 calculates the truncated phases of the horizontal and vertical fringe patterns and obtains the absolute phase distribution of the horizontal and vertical fringe patterns using a spatial phase unfolding method.

[0075] Control module 7 compares the absolute phase distribution of the horizontal red sine stripe pattern and the horizontally acquired stripe pattern, and obtains the pixel points through the phase value matching method. The corresponding phase points on the red horizontal sinusoidal fringe pattern; control module 7 compares the absolute phase distribution of the vertical red sinusoidal fringe pattern and the vertical acquisition fringe pattern to obtain the pixel points. The corresponding phase points on the vertical red sine stripe pattern, where two corresponding phase points are the same, namely the light source point E.

[0076] Step 7: Calculate the photoresist thickness.

[0077] Point and points Distance between the LCD screens in the coordinate system Light With normal The included angle and photoresist refractive index Input the thickness model from control module 7 to obtain the thickness of the photoresist at any location. This allows us to determine the uniformity of the photoresist thickness.

[0078] The thickness model is as follows: ; in, - The thickness of the photoresist; -point Time The distance; -light With normal The included angle, that is Figure 5 In ; - The refractive index is 3.

[0079] The derivation process of the thickness model is as follows: Using the right triangle relationship, we can: ; ; ; ; =1; By simultaneously solving the three equations above and simplifying, we get: ; in, -light With normal The included angle, that is Figure 5 In ; ,Right now Figure 5 In .

[0080] For a conventional and stable production line, the refractive index of the photoresist is... It is known.

[0081] For newly developed, new process introductions, or high-precision requirements of photoresist thickness and refractive index: It should be measured synchronously as an unknown quantity, which is the key to obtaining reliable thickness data.

[0082] The calculation is performed using the nonlinear least squares method, and the steps are as follows: Data preparation: Select according to measurement accuracy requirements Data ≥7 , .

[0083] make .

[0084] Establish a theoretical model: ; (3) Define residual: - ; And construct the objective function This minimizes the sum of squares of the residuals.

[0085] (4) Iterative solution: The photoresist refractive index and thickness values ​​set in the process are used as... The initial guess value, setting the physical boundary. .

[0086] Next, the following is completed automatically using a mathematical software library: For example, the `scipy.optimize.least_squares` function in Python can be used to automatically adjust parameters to minimize the objective function and output the optimal solution. .

[0087] Example 2 Substrate 2 is a non-transparent plate. Substrate 2 is made of silicon.

[0088] like Figures 3-4 , Figures 6-7 As shown, a photoresist thickness detection system includes: a stripe display module 1, a substrate 2, a photoresist 3, a control module 7, and an image acquisition device 6.

[0089] Stripe display module 1 is used to display a vertical sine stripe pattern or a horizontal sine stripe pattern; stripe display module 1 is an LCD screen.

[0090] Substrate 2 is parallel to stripe display module 1, and substrate 2 is made of non-transparent material; The upper surface of the substrate 2 is coated with photoresist 3, and the substrate 2 is located below the stripe display module 1; the center of the stripe display module 1 is offset from the optical axis of the system.

[0091] The system optical axis is the central axis of substrate 2.

[0092] The light emitted from the stripes in the stripe display module 1 passes through the photoresist 3, is reflected by the substrate 2, passes through the base photoresist 3 again, and is refracted by the photoresist 3 to the image acquisition device 6, where it is acquired.

[0093] Wherein, the optical axis is the world coordinate system. of axis; The control module 7 is connected to the image acquisition unit 6 and the stripe display module 1.

[0094] In this embodiment, the image acquisition device 6 is a pinhole camera.

[0095] The control module 7 is connected to the storage device 9, the power supply 8, the display device 11, and the human-computer interaction module 10.

[0096] In this embodiment, the number of stripes is input through the human-computer interaction module 10, and the control module 7 assigns the generated sinusoidal stripe intensity value to the red of the three primary colors of the stripe display module 1, while keeping the values ​​of the green and blue channels at 0.

[0097] Control module 7 is the CPU.

[0098] like Figure 2 As shown, the control component 5 includes an image acquisition device 6, a control module 7, a storage device 9, a power supply 8, a display device 11, and a human-computer interaction module 10.

[0099] A method for measuring photoresist thickness includes the following steps: Step 1: Using Zhang Zhengyou's camera calibration method, calibrate the camera's intrinsic and extrinsic parameters to obtain the camera's focal length. f Camera coordinate system and world coordinate system The relationship between them.

[0100] ; in, 3 3 matrices, representing the world coordinate system Rotation vector during coordinate axis transformation in the axial camera coordinate system; It is a translation vector; This indicates that the value at that position in the matrix is ​​zero.

[0101] Step 2: Determine any light source point Collect the corresponding phase points, i.e., pixels, on the stripe pattern. .

[0102] Step 3: Obtain pixels The coordinates W0 in the camera coordinate system are converted to world coordinates W1 = ( , , ).

[0103] Step 4, point Location determined: Based on the world coordinates W1 of pixel T and the pinhole position of image acquisition device 6 World coordinates W2 determine a straight line ,straight line The intersection with substrate 2 is the point ; Acquisition Points World coordinates W3 = ( , , ).

[0104] Among them, point World coordinates W2 = ( , , ) Steps 1 to 3 are the same as in Example 1, and will not be repeated here.

[0105] Step 5, point Location determined: When photoresist 3 is not placed, use the method in step 2 to locate and collect pixels on the stripe pattern. The corresponding phase points on the design stripe diagram, i.e., the light source points. ,point World coordinates W4 = ( , , ); Among them, incident light The intersection with the stripe display module 1 is point . .

[0106] like Figure 7 As shown: (1) When placing photoresist 3: Incident light Light is formed after being refracted by the upper surface of photoresist 3. ; Light Light is formed after being reflected by the upper surface of substrate 2. ; Light Light is formed after being refracted by the upper surface of photoresist 3. .

[0107] (2) When photoresist 3 is not placed: Incident light Light is formed after being reflected by the upper surface of substrate 2. .

[0108] When photoresist 3 is not placed, the light source point is calculated. World coordinates W4 = ( , , The specific steps include: 1) Using a laser rangefinder along Axis measurement LCD screen to both sides The distance between the axes is used to determine the center distance of the LCD screen. The distance between the axes is . =Right side of LCD screen Distance between axes + absolute value of the difference between the two distances / 2.

[0109] along Axis measurement to determine the left and right sides of the LCD screen The axes are equidistant, therefore the center of the LCD screen is equidistant from the center of the axis. The distance between the axes is 0.

[0110] That is, the coordinates of the center of the LCD screen in the world coordinate system are (- ,0, ),like Figure 8 As shown.

[0111] 2) Place the point Transform coordinates from the display screen coordinate system to the world coordinate system: ; ; ; In addition, when the photoresist 3 is not placed, the method in step 2 is used to locate the pixels on the stripe pattern. The corresponding phase point, i.e., the light source point. The specific steps include: 1) The LCD screen displays the horizontal and vertical red sinusoidal stripes designed in step 2 of the first scheme. Using a three-step phase-shifting technique, the image acquisition unit 6 acquires three horizontal and three vertical stripe patterns respectively. The control module 7 calculates the truncated phases of the horizontal and vertical stripe patterns and obtains the absolute phase distribution of the horizontal and vertical stripe patterns using the spatial phase unfolding method.

[0112] 2) Control module 7 compares the absolute phase distribution of the horizontal red sine stripe pattern and the horizontal acquisition stripe pattern, and obtains the pixel points through the phase value matching method. The corresponding phase points on the red horizontal sinusoidal fringe pattern; control module 7 compares the absolute phase distribution of the vertical red sinusoidal fringe pattern and the vertical acquisition fringe pattern to obtain the pixel points. On the vertical sine fringe pattern, there are corresponding phase points, where two corresponding phase points are identical, i.e., the light source point. .

[0113] Step 6: Calculate the photoresist thickness: point World coordinates W4, point World coordinates W3, point World coordinates W1, point World coordinates W2, distance from substrate 2 to stripe display module 1 Input the thickness model from control module 7 to obtain the thickness of the photoresist at any location. This allows us to determine the uniformity of the photoresist thickness.

[0114] The thickness model is as follows: ; in, - The thickness of the photoresist; -point E Axis coordinate values; -point of Axis coordinate values; -point of Axis coordinate values; -point of Axis coordinate values; -point of Axis coordinate values; -point of Axis coordinate values; - The distance between the stripe display module 1 and the substrate 2.

[0115] The derivation process of the thickness model is as follows: Based on reflected light Given the equation of the straight line, we obtain the following equation: ; Using the law of reflection, incident light rays Reflected light and Since the included angles of the axes are equal, therefore: ; From the two equations above, eliminate The thickness model formula can then be obtained.

[0116] The above are merely preferred embodiments of the present invention and do not constitute any limitation on the present invention. Any equivalent substitutions or modifications made by those skilled in the art to the technical solutions and content disclosed in the present invention without departing from the scope of the present invention shall be deemed to have remained within the protection scope of the present invention.

Claims

1. A photoresist thickness detection system, characterized in that, include: Stripe display module (1) is used to display vertical sine stripe patterns and horizontal sine stripe patterns; The substrate (2) is parallel to the stripe display module (1) and is made of a light-transmitting material or a non-light-transmitting material; When the substrate (2) is made of a light-transmitting material, the stripe display module (1) is attached to the upper surface of the substrate (2), the lower surface of the substrate (2) is coated with photoresist (3), and a standard plane mirror (4) parallel to the stripe display module (1) is provided below the photoresist (3). The center of the stripe display module (1) is offset from the optical axis of the system. The light emitted from the stripes in the stripe display module (1) passes through the substrate (2) and the photoresist (3) and is reflected by the standard plane mirror (4) to the image acquisition device (6), where it is acquired by the image acquisition device (6). When the substrate (2) is made of a non-transparent material, the upper surface of the substrate (2) is coated with photoresist (3), and the substrate (2) is located below the stripe display module (1); The center of the stripe display module (1) is off-center from the system optical axis; The light emitted from the stripes in the stripe display module (1) passes through the photoresist (3), is reflected by the substrate (2), passes through the photoresist (3) again, and is refracted by the photoresist (3) to the image acquisition unit (6), where it is acquired by the image acquisition unit (6). The system optical axis is the world coordinate system. of axis; The control module (7) is connected to the image acquisition unit (6) and the stripe display module (1).

2. The photoresist thickness detection system according to claim 1, characterized in that, The image acquisition device (6) is a pinhole camera.

3. The photoresist thickness detection system according to claim 1, characterized in that, It further includes a storage device (9), a power supply (8), a display device (11), and a human-machine interaction module (10) connected to the control module (7).

4. The photoresist thickness detection system according to claim 1, characterized in that, The stripe display module (1) is a liquid crystal display screen.

5. The photoresist thickness detection system according to claim 1, characterized in that, The control module (7) is a CPU.

6. A method for detecting photoresist thickness, based on the photoresist thickness detection system according to any one of claims 1 to 5, characterized in that, When the substrate (2) is made of a light-transmitting material, the following steps are included: Step 1: Obtain the camera's focal length and obtain the camera coordinate system. and world coordinate system The conversion relationship between them; Step 2: Find any light source point Collect the corresponding phase points, i.e., pixels, on the stripe pattern. : Step 2A: Design horizontal sinusoidal fringes, and use phase shifting technology and spatial phase unfolding algorithm to obtain the absolute phase distribution of the horizontally acquired fringe pattern; Step 2B: Design vertical sinusoidal fringes, and use phase shifting technology and spatial phase unfolding algorithm to obtain the absolute phase distribution of the vertically acquired fringe pattern; Step 2C: Compare the phase distribution of the horizontal sinusoidal fringe pattern and the horizontally acquired fringe pattern to obtain the light source point. Identify the corresponding phase points on the horizontally acquired fringe pattern; compare the phase distribution of the vertical sine fringe pattern and the vertically acquired fringe pattern to obtain the light source points. Phase points of the same name on the vertically acquired stripe pattern; Among them, two phase points with the same name are identical, i.e., pixel points. ; Step 3: Obtain pixels Based on the transformation relationship obtained in step 1, the coordinates W0 in the camera coordinate system are transformed into world coordinates W1. Specifically, based on the horizontally acquired stripe pattern, a coordinate value of coordinate W0 is obtained. Based on the vertically acquired stripe pattern, obtain another coordinate value for coordinate W0. Coordinate W0 = ( ， , ); -focal length; Step 4, point World coordinates W3 determined: Based on pixels World coordinates W1, pinhole location of image acquisition device (6) World coordinates W2 determine a straight line ,straight line The intersection point with the standard plane mirror (4) is the point. ; Acquisition Points World coordinates W3; Step 5, Light Normal to photoresist (3) The included angle Sure: straight line The angle between the ray and the normal of the standard plane mirror (4) is the angle of the ray. With normal The included angle ; Step 6, Point and points Determining the distance between them: Light The intersection of the extension of the line and the lower surface of the substrate (2) is denoted as point. ; light The intersection point with the lower surface of the substrate (2) is denoted as point. ; Finding pixels when photoresist (3) is not placed The corresponding phase points on the design stripe diagram, i.e., the light source points. ; Refracted light The corresponding incident ray is the light ray. light Intersecting with the stripe display module (1) at E; According to the law of refraction, ray tracing is performed. Parallel to light Therefore, point and points Distance between points and points The distances between them are equal, that is ; Light source point World coordinates are designated W4 = ( , , ), light source point World coordinates are marked W5 = ( , , ); ； Step 7: Calculate the photoresist thickness: Refractive index of photoresist (3) Given that point and points Distance between Light With normal The included angle and photoresist refractive index Input the thickness model in the control module (7) to obtain the photoresist thickness.

7. The photoresist thickness detection method according to claim 6, characterized in that, The thickness model is as follows: ； in, - The thickness of the photoresist; -light With normal The included angle; - The refractive index of the photoresist (3).

8. A method for detecting photoresist thickness, based on the photoresist thickness detection system according to any one of claims 1 to 5, characterized in that, When the substrate (2) is made of a non-transparent material, the following steps are included: Step 1: Obtain the camera's focal length and obtain the camera coordinate system. and world coordinate system The relationship between them; Step 2: Find any light source point Collect the corresponding phase points, i.e., pixels, on the stripe pattern. : Step 2A: Design horizontal sinusoidal fringes, and use phase shifting technology and spatial phase unfolding algorithm to obtain the absolute phase distribution of the horizontally acquired fringe pattern; Step 2B: Design vertical sinusoidal fringes, and use phase shifting technology and spatial phase unfolding algorithm to obtain the absolute phase distribution of the vertically acquired fringe pattern; Step 2C: Compare the phase distribution of the horizontal sinusoidal fringe pattern and the horizontally acquired fringe pattern to obtain the light source point. Identify the corresponding phase points on the horizontally acquired fringe pattern; compare the phase distribution of the vertical sine fringe pattern and the vertically acquired fringe pattern to obtain the light source points. Phase points of the same name on the vertically acquired stripe pattern; Among them, two phase points with the same name are identical, i.e., pixel points. ; Step 3: Obtain pixels The coordinates W0 in the camera coordinate system are converted to world coordinates W1 based on the transformation relationship obtained in step 1. Specifically, based on the horizontally acquired stripe pattern, a coordinate value of coordinate W0 is obtained. Based on the vertically acquired stripe pattern, obtain another coordinate value for coordinate W0. Coordinate W0 = ( ， , ); -focal length; Step 4, point World coordinates W3 determined: Based on pixels World coordinates W1, pinhole location of image acquisition device (6) World coordinates W2 determine a straight line The intersection of the straight line and the substrate (2) is point . ; Acquisition Points World coordinates W3; Step 5, point World coordinates W4 determined: Finding pixels when photoresist (3) is not placed The corresponding phase points on the design stripe diagram, i.e., the light source points. ,point The world coordinates are marked as W4; Step 6: Calculate the photoresist thickness: Point World coordinates W4, point World coordinates W3, point World coordinates W1, point The world coordinates W2, the distance from the substrate (2) to the stripe display module (1) Input the thickness model in the control module (7) to obtain the photoresist thickness.

9. The photoresist thickness detection method according to claim 8, characterized in that, The thickness model is as follows: ； in, - The thickness of the photoresist; -point of Axis coordinate values; -point of Axis coordinate values; -point of Axis coordinate values; -point of Axis coordinate values; -point of Axis coordinate values; -point of Axis coordinate values; - The distance between the stripe display module (1) and the substrate (2).

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