UV-LED photoetching exposure method based on microlens array and photoetching machine

Abstract

The invention provides a UV-LED photoetching exposure method based on a micro-lens array and a photoetching machine, and the method comprises the following steps: carrying out photoetching by adopting a UV-LED light source to form an exposure field with uniformly distributed light intensity; collimating an emergent light beam of the UV-LED light source through a micro lens array, and forming a rectangular exposure light spot on the surface of the mask; projecting the mask pattern on the wafer coated with the photoresist through a projection system to realize exposure; the focal plane of the projection system coincides with the wafer plane. According to the embodiment of the invention, the micro-lens array is used for replacing a laser collimation light path, so that the optical system is simple and efficient, an infinite exposure area can be realized, exposure is realized by projecting the mask pattern through the projection system, and the exposure efficiency is improved.

Description

Technical Field

[0001] The present invention relates to the field of microelectronic manufacturing technology, and more particularly, to a UV-LED lithography exposure method and a lithography machine based on a microlens array. Background Art

[0002] Exposure is an essential process in microfabrication and a key step in the lithography process. With the development of semiconductor technology, the requirements for exposure accuracy and efficiency are getting higher and higher.

[0003] In the existing exposure methods, the exposure area that can be achieved is usually limited, and during the exposure process, the mask needs to be accurately positioned on the wafer surface first. In the existing solutions, the mask alignment system can align the mask marks on the mask with the wafer marks on the wafer. Usually, a microscope is used to find the mask marks and the wafer marks, and then the centers of the two are aligned. The process of finding the marks and alignment in the above solutions relies on manual operation and confirmation, which is slow and has certain human errors, affecting the efficiency of lithography. Summary of the Invention

[0004] To solve the above problems, the present invention provides a UV-LED lithography exposure method based on a microlens array, including: performing lithography using a UV-LED light source to form an exposure field with a uniform light intensity distribution; collimating the light beam emitted by the UV-LED light source through the microlens array and forming a rectangular exposure spot on the mask surface; projecting the mask pattern onto the wafer coated with photoresist through a projection system to achieve exposure; the focal plane of the projection system coincides with the wafer plane.

[0005] Optionally, the method further includes: detecting the vertical distance between the projection system and the wafer plane through a distance detection device; adjusting the position of the projection system or the wafer plane according to the detected vertical distance so that the wafer plane is always located in the focal plane of the projection system.

[0006] Optionally, the method further includes: automatically identifying the center coordinates of the mask marks and the wafer marks through a mask alignment system, and aligning the mask marks with the wafer marks according to the center coordinates.

[0007] Optionally, the central coordinates of the mask mark and the wafer mark are automatically identified by a mask alignment system, including: obtaining trained mask mark and wafer mark pattern templates; setting operating parameters, where the operating parameters include the range of the area to be searched, the image scaling size, and the acceptance threshold for stopping the search; traversing within the range of the area to be searched to obtain a plurality of images to be searched, and performing binarization and image preprocessing on the images to be searched to obtain clear mark images; using a neural network algorithm to match each of the processed images to be searched with the mark pattern template one by one, and the image with the highest matching degree is the mask mark or the wafer mark; taking the geometric center point of the mark as the center, drawing a circular area on the image, and reducing the radius to a preset size; calculating the geometric center point of the mark within the reduced area, which is the central coordinate of the mark.

[0008] Optionally, align the mask mark with the wafer mark according to the central coordinates, including: controlling the movement of the stage according to the central coordinates of the mask mark and the wafer mark to drive the movement of the wafer, so that the mask mark coincides with the wafer mark; calibrating the coincidence degree of the mask mark and the wafer mark through a digital image processing system.

[0009] Optionally, controlling the movement of the stage according to the central coordinates of the mask mark and the wafer mark to drive the movement of the wafer, so that the mask mark coincides with the wafer mark, includes: controlling the stage to perform planar movement in the XY plane, so that the average offset in the X and Y directions between all the central points of the wafer marks and all the central points of the mask marks is equal to 0; controlling the stage to rotate around the Z axis, so that the rotation angle of the connection line of the wafer marks relative to the connection line of the mask marks is equal to 0.

[0010] Optionally, calibrating the coincidence degree of the mask mark and the wafer mark through the digital image processing system includes: obtaining a trained alignment pattern template, where the alignment pattern refers to the pattern obtained after aligning the mask mark and the wafer mark; setting operating parameters, where the operating parameters include the range of the area to be searched, the image scaling size, and the acceptance threshold for stopping the search; traversing within the range of the area to be searched to obtain a plurality of images to be searched; using a neural network algorithm to match each of the plurality of images to be searched with the alignment pattern template one by one and obtaining the matching degree; arranging the obtained matching degrees in descending order and identifying the alignment pattern.

[0011] Optionally, when the alignment pattern is identified, list one or more of the matching degree, the X or Y direction coordinate of the center of the alignment pattern, the rotation angle, the fitting error, the target coverage, the proportion of speckles, and the scaling ratio.

[0012] An embodiment of the present invention provides a UV-LED lithography machine based on a microlens array, including: a light source, using a UV-LED light source as a lithography light source; a microlens array for collimating the emitted light beam of the UV-LED; a mask alignment system for aligning mask marks with wafer marks; a projection system for projecting a mask pattern onto a wafer coated with photoresist and projecting wafer marks onto the mask plane; the mask alignment system includes: a mechanical system, a control system, a microscope group, and a digital image processing system. The mechanical system includes a mask workpiece stage for mounting a mask, a wafer workpiece stage for mounting a wafer, a first driving mechanism for driving the mask workpiece stage to move, and a second driving mechanism for driving the wafer workpiece stage. The mask and the wafer are arranged in parallel. The control system is used to control the first driving mechanism and the second driving mechanism. The microscope group is used to search for and capture images of two mask marks and two wafer marks and the alignment pattern when aligning the mask marks and the wafer marks. The digital image processing system is used to automatically identify the mask marks and the wafer marks, calculate the center coordinates of the mask marks and the wafer marks, and calibrate the coincidence degree of the mask marks and the wafer marks; the emitted light beam of the UV-LED light source forms a rectangular exposure spot on the mask surface through the microlens array, and the mask pattern is projected onto the wafer through the projection system to achieve exposure. During exposure, the wafer workpiece stage can be controlled to perform a step movement, or the mask workpiece stage and the wafer workpiece stage can perform a scanning movement in opposite directions to complete the exposure of the entire wafer.

[0013] Optionally, it further includes a distance detection device for detecting the vertical distance between the projection system and the wafer plane.

[0014] The embodiment of the present invention uses a microlens array to replace the laser collimation optical path, making the optical system simple and efficient, enabling an infinitely large exposure area, and realizing exposure by projecting a mask pattern through the projection system, thereby improving the exposure efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained according to the provided drawings without creative efforts.

[0016] Figure 1 It is a schematic flow chart of a UV-LED lithography exposure method based on a microlens array provided by an embodiment of the present invention;

[0017] Figure 2 It is a schematic structural diagram of a UV-LED lithography machine based on a microlens array provided by an embodiment of the present invention;

[0018] Figure 3 Schematic diagram of the UV-LED light source and the microlens array provided by the embodiment of the present invention;

[0019] Figures 4a - 4c Different implementation forms of electronically controlled adjustment of the exposure spot provided by the embodiment of the present invention respectively;

[0020] Figure 5 Schematic diagram before alignment of the mask mark and the wafer mark provided by the embodiment of the present invention;

[0021] Figure 6 Schematic diagram of the alignment pattern when the mask mark and the wafer mark are aligned provided by the embodiment of the present invention;

[0022] Figure 7 Schematic diagram of the stepping motion provided by the embodiment of the present invention;

[0023] Figure 8 Schematic diagram of the scanning motion provided by the embodiment of the present invention. Detailed implementation manners

[0024] To make the above objects, features and advantages of the present invention more obvious and understandable, the following will describe the specific embodiments of the present invention in detail with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0025] Figure 1 is a schematic flowchart of the UV-LED lithography exposure method based on a microlens array provided by the embodiment of the present invention. As Figure 1 shown, the method includes:

[0026] S102, using a UV-LED light source as the lithography light source to form an exposure field with a uniform light intensity distribution.

[0027] The UV-LED is an ultraviolet light-emitting diode. By using an optical array composed of multiple high-quality UV-LEDs as the UV-LED light source for lithography, it replaces the complex light source collimation optical path in the exposure system of the lithography machine. Moreover, the UV-LED light source has characteristics such as high luminous efficiency, low energy consumption, and long lifespan, and does not require preheating during use, making the exposure method of the present invention safer and more environmentally friendly. Among them, the UV-LED light source is uniformly distributed, and after being collimated by the microlens array, a parallel outgoing light beam is formed.

[0028] Exemplarily, the mask mark is carried on the mask and may include two marks distributed diagonally, and the wafer mark is carried on the wafer and also includes two marks distributed diagonally. Aligning the mask mark and the wafer mark before exposure is beneficial to improving the accuracy of lithography.

[0029] In one embodiment, the outer contour of the mask mark is square, and the wafer mark is cross-shaped. The alignment of the mask mark and the wafer mark refers to aligning the square centers of a pair of diagonally distributed mask marks with the cross-shaped centers of a pair of diagonally distributed wafer marks.

[0030] S104, collimate the light beam emitted by the UV-LED light source through the microlens array, and form a rectangular exposure spot on the mask surface.

[0031] Adjust the size of the rectangular exposure spot through the programmable area array UV-LED light source. The size of the exposure spot can also be adjusted by replacing and adjusting the electrically controlled adjustable microlens array, or by combining the microlens array with a digital micromirror array. Preferably, the size of the rectangular exposure spot is not greater than 300×300mm. In this embodiment, the microlens array is used instead of the laser collimation optical path, making the optical system simple and efficient.

[0032] S106, project the mask pattern onto the wafer coated with photoresist through the projection system to achieve exposure; the focal plane of the projection system coincides with the above-mentioned wafer plane.

[0033] The mask pattern is carried on the mask. The mask pattern can be an entire design pattern such as an integrated circuit diagram, or can be divided into multiple smaller area regions, with one or more patterns drawn in each small region. The wafer refers to the wafer used to fabricate integrated circuits of silicon or other semiconductor materials. The wafer is coated with photoresist, and pattern transfer is achieved through exposure, fixing the mask pattern on the wafer, which can be used to fabricate various circuit element structures.

[0034] Optionally, detect the vertical distance between the projection system and the wafer plane through a distance detection device; adjust the position of the projection system or the wafer plane according to the detected distance, so that the wafer plane is always located in the focal plane of the projection system. By always keeping the wafer plane in the focal plane of the microlens array, the pattern to be exposed can be completely fixed on the wafer.

[0035] The embodiment of the present invention uses a microlens array instead of a laser collimation optical path, making the optical system simple and efficient, capable of achieving an infinitely large exposure area, and achieving exposure by projecting the mask pattern through the projection system, improving the exposure efficiency.

[0036] Optionally, the above method may further include: aligning the mask mark and the wafer mark through a mask alignment system. Specifically, the mask alignment system can automatically identify the center coordinates of the mask mark and the wafer mark, and align the mask mark and the wafer mark according to the center coordinates. Exemplarily, the above steps may include:

[0037] 1. The mask is mounted on the mask stage, and the wafer is mounted on the wafer stage. Among them, the wafer stage includes: an XY moving stage, a Z-axis wafer chuck, a vacuum chuck, and a pneumatic cylinder. The vacuum chuck is mounted on the XY moving stage. The Z-axis wafer chuck is used to clamp the periphery of the wafer, and the pneumatic cylinder is used to adsorb the wafer on the vacuum chuck;

[0038] 2. Determine the position of the mask by moving the mask stage;

[0039] 3. Automatically identify the mask marks on the mask and the wafer marks on the wafer through the microscope group and the digital image processing system, and calculate the central position coordinates (X1, Y1), (X2, Y2) of the mask marks and the central position coordinates (x1, y1), (x2, y2) of the wafer marks;

[0040] 4. Control the movement of the XY moving stage according to the central position coordinates of the mask marks and the wafer marks, drive the wafer to move, so that the mask marks coincide with the wafer marks;

[0041] 5. Calibrate the coincidence degree of the mask marks and the wafer marks through the digital image processing system.

[0042] In the embodiment of the present invention, the digital image processing system is used to automatically identify and match the alignment marks and the alignment coincidence degree, which can avoid human errors, improve the alignment accuracy of the mask and the wafer marks, and improve the production efficiency and product quality at the same time.

[0043] In one embodiment, step 3 of the above-mentioned automatically identifying and calculating the central position coordinates may include:

[0044] Obtain the mask alignment mark and the wafer alignment mark templates obtained through training;

[0045] Set the operating parameters, and the operating parameters include the range of the area to be searched, the image scaling size, and the acceptance threshold for stopping the search (i.e., perform image search within the acceptance threshold range);

[0046] Traverse to obtain multiple images to be searched within the range of the area to be searched, and perform binarization and image preprocessing on the images to be searched to obtain clear mark images; among them, the images to be searched refer to the images included in the area to be searched;

[0047] Match the processed multiple images to be searched with the mark pattern or the alignment pattern template one by one through the neural network algorithm, and the image with the highest matching degree is the mask mark or the wafer mark; for example, it can also be obtained by calculating the similarity of the images. Specifically, the similarity calculation method can use the Euclidean distance, Manhattan distance, Chebyshev distance, cosine distance, etc. to measure the similarity of two images, which will not be elaborated here;

[0048] With the geometric center point of the alignment mark as the center, draw a circular area on the image and reduce the radius to a preset size;

[0049] Calculate the geometric center point of the alignment mark within the reduced area, which is the center coordinate of the alignment mark.

[0050] Furthermore, while obtaining the alignment pattern through the recognition module, parameters such as the matching degree, the X and Y direction coordinates of the center of the alignment pattern, the rotation angle, the fitting error, the target coverage, the proportion of noise, and the scaling ratio can be listed.

[0051] In one embodiment, step 4 of controlling the XY stage to move and drive the wafer to move can include:

[0052] Control the XY stage to perform a planar motion in the XY plane so that the average offset in the X and Y directions between all wafer mark center points and all mask mark center points is equal to 0. The offset of the wafer relative to the mask in the X direction ΔX = ((X1 + X2) - (x1 + x2)) / 2 = 0, and the offset of the wafer relative to the mask in the Y direction ΔY = ((Y1 + Y2) - (y1 + y2)) / 2 = 0;

[0053] Control the XY stage to rotate around the Z axis so that the rotation angle between the connection line of the wafer marks and the connection line of the mask marks is equal to 0. The rotation angle of the wafer relative to the mask Δθ = arcsin(((Y1 - y1) - (Y2 - y2)) / d) = 0, where (X1, Y1) and (X2, Y2) are the center position coordinates of the mask marks, (x1, y1) and (x2, y2) are the center position coordinates of the wafer marks, and d is the center distance between two mask marks, which is equal to the center distance between two wafer marks, d = sqrt((X2 - X1) 2 +(Y2 - Y1) 2 ) = sqrt((x2 - x1) 2 +(y2 - y1) 2 ).

[0054] In one embodiment, step 5 of calibrating the coincidence degree of the mask mark and the wafer mark through the digital image processing system can include:

[0055] Obtain the alignment pattern template obtained through training, where the alignment pattern refers to the pattern obtained after aligning the mask mark and the wafer mark;

[0056] Set the operating parameters, and the operating parameters include the range of the area to be searched, the image scaling size, and the acceptance threshold for stopping the search (i.e., performing image search within the acceptance threshold range);

[0057] Traverse within the area to be searched to obtain multiple images to be searched, scale the images to an appropriate size, and perform preprocessing, where the images to be searched refer to the images included in the area to be searched;

[0058] Match each of the multiple images to be searched with the alignment pattern template one by one through a neural network algorithm, and obtain the matching degree; for example, it can also be obtained by calculating the similarity of the images. Specifically, the similarity calculation method can use Euclidean distance, Manhattan distance, Chebyshev distance, cosine distance, etc. to measure the similarity of two images, which will not be elaborated here;

[0059] Arrange the obtained matching degrees in descending order, and identify the image with the highest matching degree as the alignment pattern.

[0060] Furthermore, when the alignment pattern is obtained through the recognition module, one or more of the matching degree, the X and Y direction coordinates of the center of the alignment pattern, the rotation angle, the fitting error, the target coverage, the proportion of speckles, and the scaling ratio can be listed.

[0061] In one embodiment, the above-mentioned obtaining the trained mask and the wafer alignment mark pattern template or alignment pattern template includes the steps of training the mark pattern or alignment pattern, specifically including:

[0062] Obtain the real alignment mark patterns on the mask and the wafer, as well as the digital images of the real alignment patterns on the wafer (which can be directly obtained by a camera), and set them as the training area;

[0063] Set the origin and coordinate system of the training area. Specifically, set the center of the alignment pattern as the origin of the training area, and establish an XY coordinate system;

[0064] Divide the training area into multiple local training areas;

[0065] Set the training parameters, including the training mode, the selection of local training areas, and the display of feature extraction results, etc. where feature extraction refers to the feature extraction of graphics;

[0066] Train each local training area, and each local training area stores at least one template obtained from the training data;

[0067] Evaluate the trained features. By calculating the template grain size obtained from the training, judge whether there is enough information for target recognition and positioning (that is, whether it can be used as an alignment pattern template). Among them, the template grain size characterizes the refinement degree of the graphics. The smaller the grain size, the greater the refinement degree. Target recognition and positioning refer to the recognition of the alignment pattern. Figure 2 It is a schematic structural diagram of a lithography machine based on a UV-LED lithography light source in an embodiment of the present invention.Figure 3 This is a schematic diagram of a UV-LED light source and a microlens array in an embodiment of the present invention. As Figure 2 and Figure 3 shown, the lithography machine includes: a UV-LED light source 1, a microlens array 2, a mask 3, a mask alignment system, and a projection system 6. Among them, the UV-LED light source 1 is used to provide an exposure field with a uniform light intensity distribution; the microlens array 2 is used to collimate the light beam emitted by the UV-LED light source 1 and form a rectangular exposure spot on the surface of the mask 3; the mask alignment system is used to align the mask mark 51 with the wafer mark 52 before exposure ( Figure 2 shows multiple alignment marks 5, including a mask mark 51 and a wafer mark 52, and only the mask mark 51 and the wafer mark 52 are schematically shown in the figure, which is not used to limit the specific shapes of the mask mark 51 and the wafer mark 52); the projection system 6 is used to project the mask pattern onto the wafer 4 coated with photoresist, and at the same time project the wafer mark 52 onto the mask mark 51. In Figure 2 a microscope group 7 is also shown.

[0068] In one embodiment, the lithography machine based on the UV-LED lithography light source further includes a distance detection device for detecting the vertical distance between the projection system 6 and the plane of the wafer 4, so that the plane where the wafer 4 is located always coincides with the focal plane of the projection system 6. The microscope group 7 can be arranged on the mask side or the wafer side. When arranged on the corresponding side, the microscope group 7 can capture the wafer mark 52 and the mask mark 51 through the projection system 6.

[0069] Optionally, the adjustment of the exposure spot can use an electrically controllable microlens array. By adjusting the focal length of the microlens array and adjusting the position of the microlens array through an actuator, the size of the outgoing light spot can be quickly adjusted to meet the requirements of different masks and different exposure methods.

[0070] Optionally, the adjustment of the exposure spot adopts a combination of a microlens array and a digital micromirror array to adjust the size of the outgoing light spot.

[0071] Optionally, the adjustment of the exposure spot uses a programmable large-area array UV-LED light source, and the size of the outgoing light spot is adjusted by controlling the array scale of the LED lighting.

[0072] Figures 4a - 4c These are schematic diagrams of three different implementation forms for electronically controlling the adjustment of the exposure spot size provided by the embodiments of the present invention.

[0073] In an alternative embodiment, as Figure 4aAs shown in the figure, the microlens array can be replaced by a combination of a liquid crystal tunable microlens array 8 and a piezoelectric actuator 9. The liquid crystal tunable microlens array 8 can electronically control the refractive index of the microlens array, thereby realizing the adjustment of the focal length of the microlens array. By electronically controlling the focal length of the liquid crystal tunable microlens array 8 and then electronically controlling the piezoelectric actuator 9 to make the focal plane position of the liquid crystal tunable microlens array 8 coincide with the UV-LED light source 1 again, the effect of adjusting the exposure spot size can be achieved.

[0074] In an alternative embodiment, as Figure 4b shown, the microlens array can be replaced by a combination of a digital micromirror array 10 and a microlens array 2. The digital micromirror array 10 consists of many small reflective mirrors, and each mirror can be deflected by a certain angle through independent electronic control. The exposure spot pattern and size can be arbitrarily adjusted by electronically controlling the digital micromirror array 10.

[0075] In an alternative embodiment, as Figure 4c shown, the UV-LED light source 1 is a programmable large-area array UV-LED light source, and the light source area covers a size of 300mm * 300mm. The size of the emitted light spot is adjusted by controlling the scale of the LED array that is lit.

[0076] The above mask alignment system includes: a mechanical system, a control system, a microscope group 7, and a digital image processing system. The mechanical system includes a mask workpiece table for mounting the mask 3, a wafer workpiece table for mounting the wafer 4, a first driving mechanism for driving the mask workpiece table to move, and a second driving mechanism for driving the wafer workpiece table to move. The mask 3 and the wafer 4 are arranged in parallel. The control system is used to control the first driving mechanism and the second driving mechanism. The microscope group 7 is used to search for and capture images of two mask marks 51 and two wafer marks 52, as well as the alignment pattern when the two mask marks 51 and the two wafer marks 52 are aligned. The digital image processing system is used to automatically identify and obtain the center position coordinates of the two mask marks 51 and the center position coordinates of the two wafer marks 52, and is also used to calibrate the coincidence degree of the two mask marks 51 and the two wafer marks 52. Before exposure, the two mask marks 51 and the two wafer marks 52 are aligned through the mask alignment system to achieve sub-micron mask alignment accuracy, laying a foundation for realizing high-precision lithography.

[0077] In one embodiment, the control system adopts a closed-loop control system, receives the center position coordinates of the two mask marks 51 and the two wafer marks 52, controls the first driving mechanism and the second driving mechanism to respectively adjust the positions of the mask workpiece table and the wafer workpiece table, and aligns the mask mark 51 and the wafer mark 52. The first driving mechanism and the second driving mechanism can adopt servo motors.

[0078] It should be noted that the driving principles of the first driving mechanism for the mask workpiece stage and the second driving mechanism for the wafer workpiece stage are both prior arts and will not be elaborated in detail in the present invention.

[0079] In one embodiment, the mask alignment system further includes a microscope group 7 for searching and photographing images of the mask mark 51 and the wafer mark 52. Since the distance between the mask and the wafer in projection exposure is relatively large, a measurement method with the objective lens above the mask is adopted. For example, the microscope group 7 is respectively installed above the two mask marks 51 of the mask 3 for searching and acquiring the patterns of the two mask marks 51 and the patterns of the wafer marks 52 projected by the projection system 6, and the position coordinates of the centers of the mask mark 51 and the wafer mark 52 are obtained through the mask mark patterns and the wafer mark patterns.

[0080] The emitted light beam of the microscope group 7 can search for the mask mark 51 on the installed mask 3 and the wafer mark 52 on the wafer 4, identify the mask mark patterns and the wafer mark patterns through a digital image processing system, and perform digital processing on the identified mask mark patterns and wafer mark patterns to obtain the center position coordinates of the two mask marks 51 and the two wafer marks 52. Moreover, the microscope group 7 can transmit the center position coordinates of the two mask marks 51 and the two wafer marks 52 to the control system, so that the control system can control the second driving mechanism to adjust the position of the wafer workpiece stage or control the first driving mechanism to adjust the position of the mask workpiece stage according to the center position coordinates of the mask mark 51 and the wafer mark 52, thereby more conveniently aligning the mask mark 51 and the wafer mark 52.

[0081] It should be noted that Figure 2 only the mask 3 and the wafer 4 are schematically shown and are not used to limit their shapes.

[0082] The mask alignment system further includes a human-machine interface, which is used to display the real-time position coordinates of the two mask marks 51, the real-time position coordinates of the two wafer marks 52, and the alignment pattern when aligning the mask mark 51 and the wafer mark 52. Figure 6 is a schematic diagram of the alignment pattern when the mask mark and the wafer mark are aligned in the present invention. As Figure 6 shown, the outer contour of the mask mark 51 is square, and the wafer mark 52 is cross-shaped. Alignment refers to the alignment of the center of the square and the center of the cross of the wafer mark.

[0083] In the present invention, there can be multiple mask marks 51 and wafer marks 52. When aligning, the mask marks 51 and the wafer marks 52 are in one-to-one correspondence.

[0084] In one embodiment, the wafer stage includes an XY stage, a Z-axis wafer chuck, a vacuum chuck, and a pneumatic cylinder. Among them, the vacuum chuck is installed on the XY stage, the Z-axis wafer chuck is used to hold the periphery of the wafer, and the pneumatic cylinder is used to adsorb the wafer 4 on the vacuum chuck. The XY stage is used to move in the XY plane to adjust the X coordinate and Y coordinate. The Z-axis wafer chuck has a high-resolution rotation axis and can adjust the rotation angle of the wafer 4. The movement of the XY stage is driven by a second driving mechanism, and at the same time, the adsorbed wafer 4 is driven to move, so that the position of the wafer mark 52 can be adjusted to align the wafer mark 52 with the mask mark 51.

[0085] Optionally, the step of aligning the mask mark with the wafer mark by a mask alignment system includes:

[0086] Alignment marks are designed on the mask and the wafer respectively. The alignment marks should be patterns of specific shapes and sizes so that they can be automatically recognized through digital image processing.

[0087] Install the mask 3 on the mask stage and install the wafer 4 on the wafer stage;

[0088] Determine the position of the mask 3 by moving the mask stage;

[0089] Automatically recognize the mask mark 51 on the mask 3 and the wafer mark 52 on the wafer 4 through the microscope group 7 and the digital image processing system, and calculate the center position coordinates of the mask mark 51 and the center position coordinates of the wafer mark 52;

[0090] Control the movement of the XY stage in the wafer stage according to the center position coordinates of the mask mark 51 and the wafer mark 52, drive the wafer 4 to move, so that the mask mark 51 coincides with the wafer mark 52 and corrects the error.

[0091] Furthermore, automatically recognizing the mask mark on the mask and the wafer mark on the wafer through the digital image processing system, and calculating the center position coordinates of the mask mark and the center position coordinates of the wafer mark includes:

[0092] 1. Obtain templates of the trained mask and wafer alignment marks;

[0093] 2. Binarize the original image to extract the mask mark and the wafer mark;

[0094] 3. Eliminate noise and irregular edges in the image through image preprocessing to obtain a clear mark image;

[0095] 4. Draw a circular area on the image with the geometric center point of the alignment mark as the center, and reduce the radius to an appropriate size;

[0096] 5. Calculate the geometric center point of the alignment mark within the reduced area, which is the center coordinate of the alignment mark.

[0097] Figure 5 It is a schematic diagram before the alignment of the mask mark and the wafer mark in the present invention. As Figure 5 shown, (X1, Y1) and (X2, Y2) refer to the center position coordinates of the mask mark 51, (x1, y1) and (x2, y2) refer to the center position coordinates of the wafer mark 52, and θ refers to the rotation angle of the line connecting the two wafer marks relative to the line connecting the two mask marks. Further, control the movement of the XY moving stage in the wafer workpiece stage according to the center position coordinates of the mask mark 51 and the wafer mark 52, drive the wafer 4 to move, so that the mask mark 51 coincides with the wafer mark 52. Specifically, it includes: controlling the XY moving stage to perform a planar movement in the XY plane, so that the average X-direction deviation and the average Y-direction deviation between the centers of the two wafer marks and the centers of the two mask marks are 0, and then controlling the XY moving stage to rotate around the Z axis so that θ = 0.

[0098] The mask alignment system can align the mask mark 51 with the wafer mark 52 through the coordinated movement of the mask workpiece stage and the XY moving stage, achieving sub-micron mask alignment accuracy and laying a foundation for realizing high-precision lithography.

[0099] Further, the step of aligning the mask mark 51 with the wafer mark 52 through the mask alignment system further includes: calibrating the coincidence degree of the mask mark 51 and the wafer mark 52 through a digital image processing system. The digital image processing system can ensure the coincidence accuracy, thereby improving the lithography accuracy.

[0100] In one embodiment, the step of aligning the mask mark 51 with the wafer mark 52 through the mask alignment system further includes: displaying the center position coordinates of the mask mark 51, the center position coordinates of the wafer mark 52, and the alignment pattern when the mask mark 51 and the wafer mark 52 are aligned through a human-machine interface. Through the human-machine interface, the alignment situation of the mask mark 51 and the wafer mark 52 can be more intuitively displayed, facilitating the control system to control the first driving mechanism and the second driving mechanism.

[0101] In an alternative embodiment, the steps of achieving a larger area exposure through step-and-repeat exposure include: dividing the surface of the wafer into a grid of a plurality of rectangular regions of the same size, and the size of the grid unit is specifically divided according to the exposure requirements; moving the wafer workpiece stage in a serpentine manner and sequentially exposing each grid unit along the serpentine route to transfer the mask pattern. Figure 7 It is a schematic diagram of the step movement in the embodiment of the present invention. As Figure 7As shown, 1 to 9 represent nine grid units respectively, and the direction of the arrow represents the direction of the stepping movement. The nine grid units 1 to 9 are exposed in sequence in a serpentine route to achieve exposure of a large exposure area.

[0102] In an optional embodiment, the step of achieving larger area exposure through scanning exposure includes: driving the mask worktable to move by a first driving mechanism, driving the wafer worktable to move by a second driving mechanism, and, during the scanning exposure, the movement direction of the mask worktable is opposite to the movement direction of the wafer worktable; scanning and exposing the mask and the wafer until the required exposure area is scanned. Figure 8 is a schematic diagram of the scanning motion in the present invention, Figure 8 The shaded portion in the figure represents the slit exposure spot 11, the arrow represents the scanning direction of the wafer stage, and the rectangular outline represents the single exposure area 12. Figure 8 As shown, the width of the slit exposure spot 11 is the same as the width of the single exposure area 12, and the length is only a small part of the length of the single exposure area 12, and the scanning direction is the width direction of the slit.

[0103] Among them, the size of the rectangular exposure spot can be electrically adjusted according to the mask size and exposure method, and the size of the spot is not greater than 300×300mm.

[0104] An embodiment of the present invention provides a UV-LED lithography machine based on a microlens array, comprising:

[0105] Light source, using UV-LED light source as the photolithography light source;

[0106] A microlens array for collimating the outgoing light beam of the UV-LED;

[0107] a mask alignment system for aligning mask marks with wafer marks;

[0108] a projection system for projecting a mask pattern onto a wafer coated with photoresist and projecting wafer marks onto a mask plane;

[0109] The mask alignment system includes: a mechanical system, a control system, a microscope group and a digital image processing system. The mechanical system includes a mask worktable for mounting a mask, a wafer worktable for mounting a wafer, a first driving mechanism for driving the mask worktable to move, and a second driving mechanism for driving the wafer worktable. The mask and the wafer are arranged in parallel. The control system is used to control the first driving mechanism and the second driving mechanism. The microscope group is used to search and take images of two mask marks and two wafer marks and an alignment pattern when aligning the mask marks and the wafer marks. The digital image processing system is used to identify the mask marks and the wafer marks, calculate the center coordinates of the marks, and calibrate the overlap between the mask marks and the wafer marks.

[0110] The emitted light beam of the UV-LED light source forms a rectangular exposure spot on the mask surface through the microlens array, and the mask pattern is projected onto the wafer through the projection system to achieve exposure. During exposure, the wafer stage can be controlled to perform a stepping motion, or the mask stage and the wafer stage can perform a scanning motion in opposite directions to complete the exposure of the entire wafer.

[0111] Optionally, it further includes a distance detection device for detecting the vertical distance between the projection system and the wafer plane.

[0112] Although the present invention is disclosed as above, the present invention is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention should be subject to the scope defined by the claims.

[0113] Finally, it should also be noted that in this text, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements not only includes those elements, but also includes other elements not expressly listed, or elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "comprising an..." does not exclude the presence of additional identical elements in the process, method, article or device comprising the element.

[0114] Each embodiment in this specification is described in a progressive manner. The key point of each embodiment is to illustrate the differences from other embodiments. The same or similar parts among the embodiments can be referred to each other. For the moving stage acceleration safety protection device disclosed in the embodiment, since it corresponds to the moving stage acceleration safety protection method disclosed in the above embodiment, the description is relatively simple, and the relevant parts can be referred to the description of the method part.

[0115] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art. The general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the broadest scope consistent with the principles and novel features disclosed herein.

Claims

1. A UV-LED lithography exposure method based on a microlens array, characterized in that, Including: Performing photolithography using a UV-LED light source to form an exposure field with a uniform light intensity distribution; Collimating the light beam emitted by the UV-LED light source through a microlens array and forming a rectangular exposure spot on the mask surface; Projecting the mask pattern onto the wafer coated with photoresist through a projection system to achieve exposure; the focal plane of the projection system coincides with the wafer plane.

2. The UV-LED lithography exposure method based on a microlens array according to claim 1, characterized in that, The method further includes: Detecting the vertical distance between the projection system and the wafer plane through a distance detection device; Adjusting the position of the projection system or the wafer plane according to the detected vertical distance so that the wafer plane is always located at the focal plane of the projection system.

3. The UV-LED lithography exposure method based on a microlens array according to claim 1, wherein, The method further includes: automatically identifying the center coordinates of the mask mark and the wafer mark through a mask alignment system, and aligning the mask mark with the wafer mark according to the center coordinates.

4. The UV-LED lithography exposure method based on a microlens array according to claim 3, wherein, Automatically identifying the center coordinates of the mask mark and the wafer mark through a mask alignment system, including: Obtaining trained mask mark and wafer mark pattern templates; Setting operating parameters, where the operating parameters include the range of the area to be searched, the image scaling size, and the acceptance threshold for stopping the search; Traversing within the range of the area to be searched to obtain a plurality of images to be searched, and performing binarization and image preprocessing on the images to be searched to obtain clear mark images; Matching the processed plurality of images to be searched with the mark pattern templates one by one through a neural network algorithm, and the image with the highest matching degree is the mask mark or the wafer mark; Drawing a circular area on the image with the geometric center point of the mark as the center, and reducing the radius to a preset size; Calculating the geometric center point of the mark within the reduced area, which is the center coordinate of the mark.

5. The UV-LED lithography exposure method based on a microlens array according to claim 4, wherein Aligning the mask mark with the wafer mark according to the center coordinates, including: Controlling the movement of the stage according to the center coordinates of the mask mark and the wafer mark to drive the wafer to move so that the mask mark coincides with the wafer mark; Calibrating the coincidence degree of the mask mark and the wafer mark through a digital image processing system.

6. The UV-LED lithography exposure method based on a microlens array according to claim 5, wherein Controlling the movement of the stage according to the center coordinates of the mask mark and the wafer mark to drive the wafer to move so that the mask mark coincides with the wafer mark, including: Controlling the stage to perform planar movement in the XY plane so that the average offset in the X direction and the Y direction between all the center points of the wafer marks and all the center points of the mask marks is equal to 0; Controlling the stage to rotate around the Z axis so that the rotation angle of the connection line of the wafer marks relative to the connection line of the mask marks is equal to 0.

7. The UV-LED lithography exposure method based on a microlens array according to claim 5, wherein Calibrating the coincidence degree of the mask mark and the wafer mark through the digital image processing system, including: Obtaining a trained alignment pattern template, where the alignment pattern refers to the pattern obtained after aligning the mask mark and the wafer mark; Setting operating parameters, where the operating parameters include the range of the area to be searched, the image scaling size, and the acceptance threshold for stopping the search; Traversing within the range of the area to be searched to obtain a plurality of images to be searched; Matching the plurality of images to be searched with the alignment pattern template one by one through a neural network algorithm and obtaining the matching degree; Arrange the obtained matching degrees in descending order and identify the alignment patterns.

8. The UV-LED lithography exposure method based on a microlens array according to claim 7, wherein, While identifying the alignment patterns, list one or more of the matching degree, the X or Y direction coordinate of the center of the alignment pattern, the rotation angle, the fitting error, the target coverage, the proportion of speckles, and the scaling ratio.

9. A UV-LED lithography machine based on a microlens array, characterized in that, It includes: A light source, using a UV-LED light source as the lithography light source; A microlens array for collimating the emitted light beam of the UV-LED; A mask alignment system for aligning the mask marks with the wafer marks; A projection system for projecting the mask pattern onto the wafer coated with photoresist and projecting the wafer marks onto the mask plane; The mask alignment system includes: a mechanical system, a control system, a microscope group, and a digital image processing system. The mechanical system includes a mask stage for mounting the mask, a wafer stage for mounting the wafer, a first driving mechanism for driving the mask stage to move, and a second driving mechanism for driving the wafer stage. The mask and the wafer are arranged in parallel. The control system is used to control the first driving mechanism and the second driving mechanism. The microscope group is used to search for and capture images of two mask marks and two wafer marks and the alignment pattern when the mask marks and the wafer marks are aligned. The digital image processing system is used to automatically identify the mask marks and the wafer marks, calculate the center coordinates of the mask marks and the wafer marks, and calibrate the coincidence degree of the mask marks and the wafer marks; The emitted light beam of the UV-LED light source forms a rectangular exposure spot on the mask surface through the microlens array, and the mask pattern is projected onto the wafer through the projection system to achieve exposure. During exposure, the wafer stage can be controlled to perform a stepping motion, or the mask stage and the wafer stage can perform a scanning motion in opposite directions to complete the exposure of the entire wafer.

10. The UV-LED lithography machine based on a microlens array according to claim 9, wherein, It further includes a distance detection device for detecting the vertical distance between the projection system and the wafer plane.

Images