Laser direct writing method, control device and laser direct writing system

Abstract

The present application relates to a laser direct writing method, a control device and a laser direct writing system, and belongs to the field of laser direct writing lithography technology. The method comprises: setting the grayscale level N of lithography, the scanning pixel step M, and the number of grayscale exposure cycles Q; dividing the grayscale image to be processed into a plurality of image strips of equal width; setting the size of the sliding extraction window during exposure; for each image strip, performing sliding extraction window grayscale extraction and data reorganization according to N, M and Q to obtain a new image strip; after the motion platform completes exposure of a new image strip in the Y direction, it moves in the X direction by a moving step XStep, the moving step XStep being the product of the image strip width W and the optical resolution R, and exposing the next new image strip until the exposure of all new image strips is completed, and the X direction is orthogonal to the Y direction; the scanning speed and the laser direct writing efficiency can be improved, and the additional number of grayscale exposure cycles of the grayscale can be achieved.

Description

[Technical field]

[0001] The present application relates to a laser direct writing method, a control device and a laser direct writing system, and belongs to the technical field of laser direct writing lithography. [Background technology]

[0002] Laser direct writing technology is one of the main technologies for making diffractive optical elements. It uses a laser beam with variable intensity to perform variable dose exposure on the resist material on the substrate surface, and after development, the required relief profile is formed on the surface of the resist layer. Laser direct writing technology is a micro-nano processing method that does not require a mask, has a wide range of applications, and is cost-effective. Due to its low cost and convenience, it has been widely used in micro-nano manufacturing fields such as mask plates, micro-electromechanical systems, micro-electromechanical systems (MEMS) devices, and micro-nano optical devices.

[0003] Currently, commonly used laser direct writing methods include laser direct writing systems based on digital micromirror devices (DMD) devices for micromirror production. Among them, DMD is a micromirror array composed of multiple high-speed digital light reflection switches, and the size of the micromirror ranges from a few microns to more than ten microns. DMD can be paired with visible LED, laser or lamp lighting for display, and can also support ultraviolet or infrared wavelengths for light control applications. It is widely used in the field of laser direct writing.

[0004] In a DMD-based laser direct writing system, the following technical solutions are usually used for exposure of grayscale graphics.

[0005] The first method is to fix the flip time of each frame of the DMD pattern and adjust the intensity of the illumination light source to achieve grayscale exposure of different depths. The above technical solution requires adjusting the power density of the transmitted light. However, the adjustment of the illumination light source power requires a certain stabilization time, which is far behind the micro-mirror flip time of the DMD in microseconds. Therefore, this technical solution often requires a static stage waiting time of seconds, and cannot achieve high-speed scanning direct writing lithography.

[0006] The second method: fix the light intensity, and achieve exposure energy of different grayscale values ​​by precisely modulating the duty cycle of each frame of DMD graphics. For example: set the total time for DMD to display a frame of graphics to 256 milliseconds, when the grayscale value is 1, the micromirror opens for 1 millisecond and closes for 255 milliseconds, when the grayscale value is 2, the micromirror opens for 2 milliseconds and closes for 254 milliseconds, and so on to achieve 256 levels of grayscale exposure energy.

[0007] However, the second technical solution still requires a certain amount of static stage time to ensure the accumulation of exposure metering within the display cycle, and cannot achieve high-speed scanning direct writing lithography.

[0008] The third method is to pixelate the exposure pattern, obtain the grayscale weight of each pixel according to the grayscale setting, and make it correspond to the number of times the micromirror is turned on. During lithography, the micromirror is moved one distance at a time and the grayscale weight is used to determine whether the current micromirror is turned on or off. In this way, grayscale lithography is achieved by superimposing exposure with at least grayscale times.

[0009] However, although the third technical solution can solve the grayscale lithography problem under high-speed scanning, it can only move one DMD pixel distance at a time during the lithography process, resulting in a low direct writing scanning speed, and the number of additional grayscale exposure cycles beyond the minimum grayscale exposure superposition number cannot be adjusted in the scanning dimension. Taking the 0.95-inch 1920 pixel × 1080 pixel DMD commonly used in the industry as an example, assuming that the size of each micromirror pixel in the DMD is 10.8um, the optical system is miniaturized 20 times, and the full frame refresh frequency is 15,000 frames, the pixel imaging resolution is 10.8 / 20 = 0.54um, and the scanning speed is 0.54 × 15000 = 8.1mm / s, which is far from enough for large-format grayscale direct writing efficiency. [Summary of the invention]

[0010] The present application provides a laser direct writing method, a control device and a laser direct writing system, which can solve the problem that the existing direct writing lithography system based on DMD as a spatial light modulator moves one pixel step at a time during grayscale scanning, resulting in low scanning speed and low direct writing efficiency; it can also solve the problem that the number of additional grayscale exposure cycles of the grayscale cannot be controlled during the scanning process, resulting in the problem that deeper microstructures can only be produced unilaterally by increasing the light source power. A new grayscale direct writing lithography method proposed in the present application, which performs pixel threshold extraction on the grayscale graphic by setting a sliding extraction window, combined with matching the corresponding DMD display window, realizes grayscale rolling direct writing lithography under multi-pixel steps, and can flexibly adjust the number of additional grayscale exposure cycles of grayscale scanning, which can improve lithography efficiency. The present application provides the following technical solutions:

[0011] In a first aspect, a laser direct writing method is provided, the method comprising:

[0012] According to the optical resolution R of the direct writing device, a grayscale image to be processed is obtained;

[0013] Set the grayscale level N of the lithography, set the scanning pixel step M, and set the number of grayscale exposure cycles Q, so that M*(N-1)*Q is less than or equal to the height of the spatial light modulator display window;

[0014] Dividing the grayscale image into a plurality of image strips of equal width, wherein the width W of the image strip is less than or equal to the width of the display window of the spatial light modulator;

[0015] Set the size of the sliding extraction window during exposure;

[0016] For each of the image strips, grayscale extraction with a sliding extraction window and data reorganization are performed according to the grayscale level N, the scanning pixel step M and the grayscale exposure cycle number Q to obtain a new image strip;

[0017] After the moving platform completes the exposure of a new image strip in the Y direction, it moves a moving step XStep in the X direction, where the moving step XStep is the product of the graphic strip width W and the optical resolution R, and exposes the next new image strip until the exposure of all new image strips is completed. The X direction and the Y direction are orthogonal.

[0018] Optionally, the setting of the size of the sliding extraction window during exposure includes:

[0019] The height of the sliding extraction window is set to M*(N-1)*Q, and the width is set to the image strip width W.

[0020] Optionally, for each of the image strips, performing sliding extraction window grayscale extraction and data reorganization according to the grayscale level N, the scanning pixel step M and the number of grayscale exposure cycles Q to obtain a new image strip includes:

[0021] Divide the grayscale to obtain N-1 grayscale thresholds, grayscale threshold G i =i*G in , 1≤i≤N-1, where G in is the size of the grayscale interval, G in =Total number of grayscales G / grayscale level N;

[0022] Periodically performing grayscale extraction in sequence from the bottom of the image strip according to the sliding extraction window to obtain binary data, and sequentially placing the binary data into a new image strip from the bottom, the specific steps include:

[0023] Starting from the bottom of the image strip, grayscale threshold judgment is performed according to the sliding extraction window, data greater than or equal to the first grayscale threshold G1 is set, and data less than the first grayscale threshold G1 is set to zero, to obtain new binary data with a width of W and a height of M*(N-1)*Q; the binary data is placed at the bottom of a new image strip;

[0024] Control the sliding extraction window to move upward by M pixels to perform grayscale threshold judgment, set the data greater than or equal to the second grayscale threshold G2, and set the data less than the second grayscale threshold G2 to zero, to obtain new binary data with a width of W and a height of M*(N-1)*Q; put the binary data into the new image strip in sequence;

[0025] Repeat N-1 times to complete one cycle of grayscale extraction;

[0026] The sliding extraction window moves upward by M pixels, and performs the next periodic grayscale extraction until all the current strip data are extracted, and the new image strip is obtained.

[0027] Optionally, before performing grayscale threshold determination according to the sliding extraction window starting from the bottom of the image strip, the method further includes:

[0028] M*(N-1)*Q lines of blank data are added to the head of the image strip.

[0029] Optionally, the step of repeating the above grayscale extraction until all current strip data is extracted includes:

[0030] When the end of the image strip does not meet the height of the sliding extraction window, blank data is rounded up to M*(N-1)*Q.

[0031] Optionally, the setting data corresponds to turning on the DMD spatial light modulator, and the zeroing data corresponds to turning off the DMD spatial light modulator.

[0032] Optionally, the method further comprises:

[0033] For each of the new image strips, the motion platform is controlled to perform scanning motion in the Y direction, and the scanning step YStep of the motion platform in the Y direction is the product of the scanning pixel step M and the optical resolution R. Every time the scanning step YStep is moved, a synchronization signal is triggered to extract an image with the same size as the sliding extraction window in the order of the new graphic strips from bottom to top, and the image is triggered to be displayed on the spatial light modulator, and the laser performs pulse synchronous exposure at the same time.

[0034] Optionally, acquiring the grayscale image to be processed according to the optical resolution R of the direct writing device includes:

[0035] The processed image is grayscaled according to the optical resolution R to obtain the grayscale image.

[0036] In a second aspect, a control device is provided, the control device comprising a processor and a memory; a program is stored in the memory, and the program is loaded and executed by the processor to implement the laser direct writing method provided in the first aspect.

[0037] In a third aspect, a laser direct writing system is provided, wherein the laser direct writing system adopts the laser direct writing method provided in the first aspect.

[0038] The beneficial effects of the present application include at least: obtaining a grayscale image to be processed according to the optical resolution R of the direct writing device; setting the grayscale level N of the lithography, setting the scanning pixel step M, and setting the number of grayscale exposure cycles Q, so that M*(N-1)*Q is less than or equal to the height of the spatial light modulator display window; dividing the grayscale image into a plurality of image strips of equal width, and the image strip width W is less than or equal to the width of the spatial light modulator display window; setting the size of the sliding extraction window during exposure; for each image strip, performing sliding extraction window grayscale extraction and data reorganization according to the grayscale level N, the scanning pixel step M and the number of grayscale exposure cycles Q to obtain a new image strip; a motion platform After a new image strip is exposed in the Y direction, a moving step XStep is moved in the X direction, where the moving step XStep is the product of the graphic strip width W and the optical resolution R, and the next new image strip is exposed until all new image strips are exposed, and the X direction is orthogonal to the Y direction. The problem of low scanning speed and low direct writing efficiency caused by moving one pixel step each time when performing grayscale scanning in the existing direct writing lithography system based on DMD as a spatial light modulator can be solved. Since the sliding extraction window can slide based on the pixel step required by the user, the scanning speed can be increased, thereby improving the laser direct writing efficiency.

[0039] At the same time, it can also solve the problem that the additional grayscale exposure cycle number of the grayscale cannot be controlled during the scanning process, resulting in the problem that the production of deeper microstructures can only be achieved unilaterally by increasing the light source power; because the sliding extraction window can repeatedly expose each pixel based on the number of grayscale exposure cycles, it is possible to control the additional grayscale exposure cycle number of the grayscale during the scanning process.

[0040] In addition, when the pixel height of the image strip cannot meet the window height at the last slide, blank data is added to the scan end position of the image strip, so that the data integrity of the last image strip can be guaranteed.

[0041] In addition, by adding blank data at the scanning start position of the image strip according to the window height, each effective pixel row can meet the requirement of the number of grayscale exposure cycles.

[0042] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application and implement it according to the contents of the specification, the following is a detailed description of the preferred embodiments of the present application in conjunction with the accompanying drawings.

Brief Description of the Drawings

[0043] Figure 1 It is a structural schematic diagram of a laser direct writing system provided by an embodiment of the present application;

[0044] Figure 2 is a flow chart of a laser direct writing method provided by an embodiment of the present application;

[0045] Figure 3 is a schematic diagram of a grayscale image provided by an embodiment of the present application;

[0046] Figure 4 is a schematic diagram of a pixel matrix file provided by an embodiment of the present application;

[0047] Figure 5 is a schematic diagram of a unit bitmap exposure process when the number of grayscale exposure cycles is 1 provided by an embodiment of the present application;

[0048] Figure 6 Schematic diagram of a unit bitmap exposure process when the number of grayscale exposure cycles is Q (Q>1) provided by an embodiment of the present application

[0049] Figure 7 is a schematic diagram of grayscale data extraction provided by an embodiment of the present application;

[0050] Figure 8 It is a schematic diagram of grayscale data extraction provided by another embodiment of the present application. [Specific implementation method]

[0051] The specific implementation methods of the present application are further described in detail below in conjunction with the accompanying drawings and examples. The following examples are used to illustrate the present application but are not intended to limit the scope of the present application.

[0052] The laser direct method provided in the present application is used in a maskless exposure system. The maskless exposure system can use a DMD or an LCD as a pattern generator (or spatial light modulator). Since the effective reflectivity of each micromirror of the DMD is much higher than that of the LCD, and the accuracy of the DMD in controlling the grayscale of pixels is also higher than that of the LCD, the present application uses the DMD as an example of a pattern generator of a virtual mask for explanation.

[0053] Figure 1 It is a schematic diagram of the structure of a laser direct writing system provided in one embodiment of the present application, the system at least comprising: an exposure light source 110, a spatial light modulator 120, an optical imaging system 130, a motion platform 140, and a control device 150.

[0054] The exposure light source 110 is used to project light toward the spatial light modulator 120 .

[0055] Optionally, the exposure light source 110 may be a laser, and the laser light emitted by the laser may be filtered and / or collimated before being irradiated to the spatial light modulator 120 .

[0056] The light emitted by the exposure light source 110 is modulated by the spatial light modulator 120 and then irradiated onto the imaging surface through the optical imaging system 130 .

[0057] The spatial light modulator 120 may be a DMD pattern generator including a plurality of micromirrors, each of which may be in an on position or a off position. When the micromirror is in an on position, the reflected light passes through the optical imaging system 130 to the imaging surface; when the micromirror is in an off position, the reflected light does not enter the optical imaging system 130.

[0058] The optical imaging system 130 is composed of a group of optical lenses, and is used to project the light modulated by the spatial light modulator 120 onto an imaging surface.

[0059] The motion platform 140 is provided with an imaging surface, such as a photoresist plate, etc. The control device 150 is respectively connected to the spatial light modulator 120 and the motion platform 140 for communication, so as to control the working state of the spatial light modulator 120 and the working state of the motion platform 140. For example, the control device 150 controls each micromirror in the spatial light modulator 120 to be in an on state or an off state, and controls the motion direction and motion distance of the motion platform 140.

[0060] Optionally, the control device for controlling the spatial light modulator 120 and the control device for controlling the motion platform 140 can be implemented in the same device, or can also be implemented in different devices. For example, the control device for controlling the spatial light modulator 120 is a data processing workstation, and the control device for controlling the motion platform 140 is an industrial computer. This embodiment does not limit the implementation method of the control device.

[0061] In this embodiment, the control device is used to: obtain a grayscale image to be processed according to the optical resolution R of the direct writing device; set the grayscale level N of the lithography, set the scanning pixel step M, and set the number of grayscale exposure cycles Q, so that M*(N-1)*Q is less than or equal to the height of the spatial light modulator display window; divide the grayscale image into a plurality of image strips of equal width, and the image strip width W is less than or equal to the width of the spatial light modulator display window; set the size of the sliding extraction window during exposure; for each image strip, perform sliding extraction window grayscale extraction and data reorganization according to the grayscale level N, the scanning pixel step M and the number of grayscale exposure cycles Q to obtain a new image strip; after the motion platform completes the exposure of a new image strip in the Y direction, it moves a moving step XStep in the X direction, the moving step XStep is the product of the image strip width W and the optical resolution R, and exposes the next new image strip until the exposure of all new image strips is completed, and the X direction is orthogonal to the Y direction.

[0062] In this embodiment, grayscale rolling direct writing lithography with multi-pixel step can be realized, and the number of grayscale exposure cycles of grayscale scanning can be flexibly adjusted to improve the efficiency and depth of grayscale scanning lithography currently performed using a spatial light modulator.

[0063] The laser direct writing method implemented by the above control device is described in detail below. In addition, it is worth noting that the above laser direct writing system is only illustrative, and in actual implementation, the laser direct writing system may also include other components, which are not listed one by one in this embodiment.

[0064] Figure 2 is a flow chart of a laser direct writing method provided by an embodiment of the present application. Figure 1 Taking the control device in the laser direct system shown in FIG. 1 as an example, the method includes at least the following steps:

[0065] Step 201 : acquiring a grayscale image to be processed according to the optical resolution R of the direct writing device.

[0066] Grayscale images (or grayscale images) are generally divided into 256 grayscales. In other embodiments, they may also be other grayscale numbers. Figure 3 The grayscale image shown has 256 grayscale levels.

[0067] In one example, according to the optical resolution R of the direct writing device, the grayscale image to be processed is obtained, including: grayscale processing is performed on the processed image according to the optical resolution R to obtain the grayscale image.

[0068] Specifically, the control device obtains the micromirror size of the spatial light modulator, the miniaturization factor of the optical imaging system, and the image size of the processed image; determines the optical resolution R based on the micromirror size and the miniaturization factor; uses the image size and the optical resolution to determine the pixel width and pixel height of the grayscale image, converts the processed image into a grayscale image according to a preset order, and obtains a pixel dot matrix file. The pixel dot matrix file is as follows: Figure 4 shown.

[0069] The optical resolution is the value of the micromirror size divided by the miniaturization factor. The pixel width is the integer value of the image width divided by the optical resolution. The pixel height is the integer value of the image height divided by the optical resolution.

[0070] For example: a 0.95-inch spatial light modulator has a display window width of 1920 pixels, a display window height of 1080 pixels, and a size of each pixel of 10.8um. ​​Assume that the optical miniaturization rate of the system is 20 times, that is, the light reflected by each micromirror in the spatial light modulator is miniaturized 20 times after adjustment by the optical imaging system 130. At this time, the optical resolution of the system is 10.8um / 20=0.54um. If the image size of the processed image is 10mm×10mm, according to the optical resolution of the system, the pixel width of the bitmap (Bitmap, BMP) is 10mm / 0.54um=18519 pixels, and the pixel height is 10mm / 0.54um=18519 pixels. When converting the processed image to a grayscale image, the grayscale value of 255 of the grayscale image corresponds to a height of 10um, the grayscale value of 0 of the grayscale image corresponds to a height of 0um, and other grayscale values ​​correspond according to the linear calculation of the height.

[0071] Step 202, setting the grayscale level N of the lithography, setting the scanning pixel step M, and setting the number of grayscale exposure cycles Q, so that M*(N-1)*Q is less than or equal to the height of the display window of the spatial light modulator.

[0072] Wherein, N, M and Q are all positive integers.

[0073] Step 203: divide the grayscale image into a plurality of image strips of equal width, wherein the image strip width W is less than or equal to the width of the display window of the spatial light modulator.

[0074] In one example, the grayscale image is divided into an image strip every strip width W in the pixel width direction to obtain at least one image strip. When the pixel width of the last image strip cannot meet the strip width, blank data is added to the end position in the width direction of the grayscale image so that the pixel width of the last image strip meets the strip width.

[0075] For example: the pixel width of the grayscale graphic is 18519 pixels, and the width of the display window is 1920 pixels. At this time, the grayscale image is divided every 1920 pixels. Since 18519 / 1920=9*1920+1239, that is, 10 image strips can be obtained, and the last image strip needs to add 1920-1239=681 columns of blank data to make the pixel width of the last image strip meet the strip width.

[0076] In another example, the strip width of the image strip is not fixed, and it only needs to satisfy that the strip width of the image strip is less than or equal to the width of the display window.

[0077] Step 204, setting the size of the sliding extraction window during exposure.

[0078] Specifically, in this embodiment, based on the grayscale level N of this lithography, the pixel step M during scanning, and the number of grayscale exposure cycles Q of this lithography, the window height M*(N-1)*Q of the sliding extraction window of the image strip is determined; the window width of the sliding extraction window is the strip width W.

[0079] The sliding extraction window is used to slide and extract the grayscale value every pixel step M in each image strip and perform binarization processing.

[0080] In this embodiment, the grayscale level, pixel step and number of grayscale exposure cycles can be set based on user needs. For example, when the grayscale image accuracy that needs to be photolithographic is higher, more grayscale levels can be set; when a higher photolithography speed is required, a larger pixel step can be set; when a deeper photolithography depth is required, more grayscale exposure cycles can be set.

[0081] In other embodiments, the grayscale level, pixel pitch and number of grayscale exposure cycles may also be fixed values. This embodiment does not limit the setting method of the grayscale level, pixel pitch and number of grayscale exposure cycles.

[0082] Step 205 , for each image strip, grayscale extraction and data reorganization are performed using a sliding extraction window according to the grayscale level N, the scanning pixel step M and the number of grayscale exposure cycles Q to obtain a new image strip.

[0083] For each image strip, according to the grayscale level N, the scanning pixel step M and the number of grayscale exposure cycles Q, the sliding extraction window grayscale extraction and data reorganization are performed to obtain a new image strip, including the following steps:

[0084] Step 1: Divide the grayscale to obtain N-1 grayscale thresholds. i =i*G in , 1≤i≤N-1, where G in is the size of the grayscale interval, G in =Total number of grayscales G / grayscale level N.

[0085] In one example, grayscale area division includes: determining a grayscale threshold G i .

[0086] For example: if the number of grayscale is 256 and the grayscale level is 4, then G in The value of is 256 / 4=64, then the first grayscale threshold is 64, the second grayscale threshold is 128, and the third grayscale threshold is 192.

[0087] Step 2, starting from the bottom of the image strip, periodically extracting grayscale in the sliding extraction window to obtain binary data, and sequentially putting the binary data into a new image strip starting from the bottom, specifically comprising:

[0088] a. Starting from the bottom of the image strip, grayscale threshold judgment is performed according to the sliding extraction window, and data greater than or equal to the first grayscale threshold G1 is set, and data less than the first grayscale threshold G1 is set to zero, to obtain new binary data with a width of W and a height of M*(N-1)*Q; the binary data is placed at the bottom of the new image strip.

[0089] At this time, a frame of binary data with a pixel width of W and a pixel height of M*(N-1)*Q obtained by the first extraction is generated. Among them, the set data corresponds to the DMD spatial light modulator being turned on, specifically, the DMD micromirror at the corresponding position is turned on, and the zero data corresponds to the DMD spatial light modulator being turned off, specifically, the DMD micromirror at the corresponding position is turned off.

[0090] b. Control the sliding extraction window to move upward by M pixels to perform grayscale threshold judgment, set the data greater than or equal to the second grayscale threshold G2, and set the data less than the second grayscale threshold G2 to zero, to obtain new binary data with a width of W and a height of M*(N-1)*Q; put the binary data into the new image strip in sequence.

[0091] c. Repeat N-1 times to complete one cycle of grayscale extraction.

[0092] Step 3: The sliding extraction window moves upward by M pixels, and performs the next cycle grayscale extraction until all the current strip data is extracted and a new image strip is obtained.

[0093] That is, during the Nth grayscale extraction, the sliding extraction window is controlled to move upward by M pixels and extraction starts again with the first grayscale threshold, and the above grayscale extraction steps are repeated until all the current strip data are extracted to obtain a new image strip.

[0094] Each image strip in a grayscale image is extracted according to the above process to obtain binary data corresponding to each image strip.

[0095] The number of grayscale exposure cycles Q refers to multiple periodic grayscale exposures at the same position of the image. If one cycle of grayscale exposure is performed, the number of grayscale exposure cycles Q = 1; if two cycles of grayscale exposure are performed, the number of grayscale exposure cycles Q = 2; and so on. The greater the number of grayscale exposure cycles, the deeper the depth of the lithography. Figure 5As shown, when the number of grayscale exposure cycles Q is 1, the height of the extraction window is (N-1)*M. Taking one of the unit bitmaps (the gray area in the figure) as an example, in the Y-axis scanning direction, the gray area in the figure extracts the grayscale value of the first threshold, and the sliding window moves upward by one pixel scanning step M, and then extracts the grayscale value of the second threshold, and then moves upward by one pixel scanning step M until the grayscale value extraction of the N-1th threshold is completed, that is, the unit bitmap (the gray area in the figure) completes one cycle of grayscale value extraction, corresponding to one cycle of grayscale metering exposure for the unit bitmap during lithography, that is, one grayscale exposure.

[0096] In such Figure 6 As shown, when the number of grayscale exposure cycles is Q (Q>1), the height of the extraction window is (N-1)*M*Q. Taking one of the unit bitmaps (the gray area in the figure) as an example, in the Y-axis scanning direction, the gray area in the figure extracts the grayscale value of the first threshold, and the sliding window moves upward by a pixel scanning step M, and then extracts the grayscale value of the second threshold, and then moves upward by a pixel scanning step M until the grayscale value extraction of the N-1th threshold is completed, that is, the unit bitmap (the gray area in the figure) completes the extraction of the grayscale value of one cycle; the unit bitmap (the gray area in the figure) re-extracts the grayscale value of the first threshold... until the grayscale value extraction of the N-1th threshold, completing the grayscale value extraction of the second cycle; repeat the extraction steps until Q periodic grayscale extractions are performed, corresponding to the grayscale metering exposure of Q cycles of the unit bitmap during lithography, that is, Q grayscale exposures.

[0097] Optionally, when the pixel height of the image strip cannot meet the window height at the last slide, the control device can add blank data to the scan end position of the image strip to make the pixel height of the image strip meet the window height at the last slide.

[0098] Step 206: After the motion platform completes exposure of a new image strip in the Y direction, it moves a moving step XStep in the X direction, where the moving step XStep is the product of the graphic strip width W and the optical resolution R, and exposes the next new image strip until the exposure of all new image strips is completed. The X direction is orthogonal to the Y direction.

[0099] Specifically, for each new image strip, the motion platform is controlled to perform scanning movement in the Y direction. The scanning step YStep of the motion platform in the Y direction is the product of the scanning pixel step M and the optical resolution R. Every time the scanning step YStep is moved, a synchronization signal is triggered to extract an image with the same size as the sliding extraction window in the order of the new graphic strips from bottom to top, and trigger the image to be displayed on the spatial light modulator, while the laser performs pulse synchronous exposure.

[0100] In summary, the laser direct writing method provided in this embodiment obtains the grayscale image to be processed according to the optical resolution R of the direct writing device; sets the grayscale level N of the lithography, sets the scanning pixel step M, and sets the number of grayscale exposure cycles Q, so that M*(N-1)*Q is less than or equal to the height of the spatial light modulator display window; divides the grayscale image into a plurality of image strips of equal width, and the image strip width W is less than or equal to the width of the spatial light modulator display window; sets the size of the sliding extraction window during exposure; for each image strip, performs sliding extraction window grayscale extraction and data reorganization according to the grayscale level N, the scanning pixel step M and the number of grayscale exposure cycles Q to obtain a new image strip; and operates After the moving platform completes the exposure of a new image strip in the Y direction, it moves a moving step XStep in the X direction, where the moving step XStep is the product of the graphic strip width W and the optical resolution R, and exposes the next new image strip until the exposure of all new image strips is completed, and the X direction is orthogonal to the Y direction. The problem of low scanning speed and low direct writing efficiency caused by moving one pixel step each time when performing grayscale scanning in the existing direct writing lithography system based on DMD as a spatial light modulator can be solved. Since the sliding extraction window can slide based on the pixel step required by the user, the scanning speed can be increased, thereby improving the laser direct writing efficiency.

[0101] At the same time, it can also solve the problem that the additional grayscale exposure cycle number of the grayscale cannot be controlled during the scanning process, resulting in the problem that the production of deeper microstructures can only be achieved unilaterally by increasing the light source power; because the sliding extraction window can repeatedly expose each pixel based on the number of grayscale exposure cycles, it is possible to control the additional grayscale exposure cycle number of the grayscale during the scanning process.

[0102] In addition, when the pixel height of the image strip cannot meet the window height at the last slide, blank data is added to the scan end position of the image strip, so that the data integrity of the last image strip can be guaranteed.

[0103] In order to more clearly understand the laser direct writing method provided by the present application, the method is illustrated with several examples below. In the following example, a 0.95-inch DMD graphic generator is used, the width of the DMD display window is 1920 pixels, the height of the DMD display window is 1080 pixels, the pixel size is 10.8um, the system optical miniaturization ratio is 20 times, and the optical resolution R is 10.8um / 20=0.54um. The system light source is a 355nm wavelength ultraviolet pulse laser, the motion platform includes an XY high-precision linear motion platform, and a Z-axis focusing module.

[0104] Example 1: Assume that the original processed image size is 10mm×10mm, the deepest structure is 10um, the file format is stl, the grayscale level N=4, the pixel step M=3, and the number of grayscale exposure cycles Q=1. Figure 7 Taking a column in BMP as an example, the laser direct writing method includes at least the following steps:

[0105] Step 1, convert the stl file into a 256-grayscale grayscale image (BMP image), such as Figure 3 shown.

[0106] The pixel width of the grayscale image is 10mm / 0.54um=18519 pixels, and the pixel height is 10mm / 0.54um=18519 pixels. At this time, the BMP grayscale value 255 corresponds to 10um height, the BMP grayscale value 0 corresponds to 0um height, and other grayscale values ​​correspond to linear calculations based on height.

[0107] Step 2: Crop the grayscale image into image strips with a width of 1920 pixels, and the number of image strips = 18519 / 1920 = 10.

[0108] In this example, cropping according to the width of the display window is taken as an example. In actual implementation, the value may also be smaller than the width of the display window. This embodiment does not limit the cropping size.

[0109] Step 3, set the window width of the sliding extraction window to 1920 pixels and the window height to M*(N-1)*Q=9 pixels.

[0110] Step 4, divide the grayscale, and obtain a grayscale threshold every 256 / 4=64 grayscale divisions, and obtain 3 grayscale thresholds, which are distributed as the first grayscale threshold of 64, the second grayscale threshold of 128, and the third grayscale threshold of 192.

[0111] Step 5: Starting from the bottom of the first image strip, grayscale threshold judgment and extraction are performed according to the sliding extraction window. The pixel points with grayscale values ​​less than the first grayscale threshold value 64 within the sliding extraction window are set to 0, and the rest are set to 1, to obtain new normalized 1920×9 binary data.

[0112] Step 6: Slide the extraction window upward by 3 pixels and perform grayscale threshold judgment extraction again. The pixel points with grayscale values ​​less than the second grayscale threshold 128 in the window range are set to 0, and the rest are set to 1, to obtain new normalized 1920×9 binary data.

[0113] Step 7: The sliding extraction window is moved upward by 3 pixels again, and the grayscale threshold is judged and extracted again. The pixel points with grayscale values ​​less than the third grayscale threshold 192 in the window range are set to 0, and the rest are set to 1, to obtain the new normalized 1920×9 binary data. One cycle of grayscale extraction is completed.

[0114] Step 8: Slide the extraction window upward by 3 pixels again and start extraction again according to the first grayscale threshold.

[0115] Step 9, repeat the above steps until the data extraction of the entire image strip is completed. The extracted data is reassembled in order to form the final DMD display data, such as Figure 7 .

[0116] Step 10, repeat the same steps to complete the extraction of all bands.

[0117] Step 11, setting the size of the display window area of ​​each frame on the DMD image generator, that is, pixel width W = 1920 pixels, pixel height = M*(N-1)*Q = 9 pixels.

[0118] Step 12, the scanning step of the moving platform in the Y direction is YStep=M×R=3×0.54um=1.62um. A synchronization signal is sent out every time the scanning step YStep is moved to extract an image of the same size as the sliding extraction window in the order of the new graphic strips from bottom to top, and trigger the image to be displayed on the spatial light modulator. At the same time, the laser performs pulse synchronous exposure.

[0119] Step 13, after a new image strip is exposed in the Y direction, the motion platform returns to the bottom and moves a moving step XStep in the X direction, XStep = W × R = 1920 × 0.54 = 1036.8 um, and the next new image strip is exposed in the same manner as step 12 until all new image strips are exposed.

[0120] Example 2: Assume that the original processed image size is 10mm×10mm, the deepest structure is 10um, the file format is stl, the grayscale level N=4, the pixel step M=3, and the number of grayscale exposure cycles Q=2 times. Figure 8 Taking a column in the BMP diagram as an example, the laser direct writing method includes at least the following steps:

[0121] Step 1, convert the stl file into a grayscale image (BMP image) with 256 gray levels.

[0122] For detailed description of this step, please refer to step 1 of Example 1, which will not be repeated here in this embodiment.

[0123] Step 2: Crop the grayscale image into image strips with a width of 1920 pixels, and the number of strips = 18519 / 1920 = 10.

[0124] Step 3, set the window width of the sliding extraction window to 1920 pixels and the window height to M*(N-1)*Q=18 pixels.

[0125] Step 4, divide the grayscale into regions, and obtain a grayscale threshold for every 256 / 4=64 grayscale divisions, and obtain 3 grayscale thresholds, which are distributed as the first grayscale threshold of 64, the second grayscale threshold of 128, and the third grayscale threshold of 192.

[0126] Step 5: Starting from the bottom of the first image strip, grayscale threshold judgment and extraction are performed according to the sliding extraction window. The pixels whose grayscale values ​​within the sliding extraction window are less than the first grayscale threshold 64 are set to 0, and the rest are set to 1, to obtain new normalized 1920×18 binary data.

[0127] Step 6: Slide the extraction window upward by 3 pixels and perform grayscale threshold judgment extraction again. The pixel points with grayscale values ​​less than the second grayscale threshold 128 in the window range are set to 0, and the rest are set to 1, to obtain new normalized 1920×18 binary data.

[0128] Step 7, the sliding extraction window is moved upward by 3 pixels again, and the grayscale threshold is judged and extracted again. The pixel points with grayscale values ​​less than the third grayscale threshold 192 in the window range are set to 0, and the rest are set to 1, and the new normalized 1920×18 binary data is obtained. One cycle of grayscale extraction is completed.

[0129] Step 8: Slide the extraction window upward by 3 pixels again and start extraction again according to the first grayscale threshold.

[0130] Step 9, repeat the above steps until the data extraction of the entire image strip is completed. The extracted data is reassembled in order to form the final DMD display data.

[0131] Step 10, repeat the same steps to complete the extraction of all bands.

[0132] Step 11, setting the size of the display window area of ​​each frame on the DMD image generator, that is, pixel width W = 1920 pixels, pixel height = M*(N-1)*Q = 18 pixels.

[0133] Step 12, the scanning step of the moving platform in the Y direction is YStep=M×R=3×0.54um=1.62um. A synchronization signal is sent out every time the scanning step YStep is moved to extract an image of the same size as the sliding extraction window in the order of the new graphic strips from bottom to top, and trigger the image to be displayed on the spatial light modulator. At the same time, the laser performs pulse synchronous exposure.

[0134] Step 13, after a new image strip is exposed in the Y direction, the motion platform returns to the bottom and moves a moving step XStep in the X direction, XStep = W × R = 1920 × 0.54 = 1036.8 um, and the next new image strip is exposed in the same manner as step 12 until all new image strips are exposed.

[0135] According to the process of Example 2, for the same row of pixels, two cycles of grayscale extraction are performed on the row of pixels, and a cycle of grayscale metering exposure is performed during lithography, that is, the number of grayscale exposure cycles is 2 times.

[0136] In addition, according to Example 2, some pixel rows may not meet the requirement of the number of grayscale exposure cycles. Based on this, in this embodiment, for each image strip, before the grayscale threshold is determined according to the sliding extraction window from the bottom of the image strip, it also includes: adding M*(N-1)*Q rows of blank data to the head of the image strip. In this way, each valid pixel row can meet the requirement of the number of grayscale exposure cycles.

[0137] Example 3: Assume that the original processed image size is 30000 pixels × 30000 pixels, the maximum grayscale is 256, the file format is BMP, the grayscale level N = 64 grayscales, the pixel step M = 4 pixel scanning step, and the number of grayscale exposure cycles Q = 3 times of superimposed exposure. The laser direct writing method includes at least the following steps:

[0138] Step 1: Crop the BMP image into image strips with a width of 1920 pixels, and the number of strips = 30000 / 1920 = 16.

[0139] Step 2, set the window width of the sliding extraction window to 1920 pixels and the window height to M*(N-1)*Q=756 pixels.

[0140] Step 3, divide the grayscale, that is, obtain a grayscale threshold every 256 / 64=4 grayscale divisions, and obtain 63 grayscale thresholds, which are distributed as the first grayscale threshold 4, the second grayscale threshold 8, the third grayscale threshold 12, ..., and the 63rd grayscale threshold is 252.

[0141] Step 4: Starting from the bottom of the first BMP image strip, grayscale threshold judgment and extraction are performed according to the sliding extraction window. The pixel points with grayscale values ​​less than the first grayscale threshold 4 within the window range are set to 0, and the rest are set to 1, to obtain the new normalized 1920×756 binary data.

[0142] Step 5: Slide the extraction window upward by 4 pixels and perform grayscale threshold judgment extraction again. The pixel points with grayscale values ​​less than the second grayscale threshold 8 in the window range are set to 0, and the rest are set to 1, to obtain new normalized 1920×756 binary data.

[0143] Step 6, repeat the above steps, move the sliding extraction window, until the pixel points with grayscale values ​​less than the 63rd grayscale threshold 252 in the window range are set to 0, and the rest are set to 1, to obtain new normalized 1920×756 binary data. One cycle of grayscale extraction is completed.

[0144] Step 7, slide the extraction window upward by 4 pixels and start extraction again according to the first grayscale threshold.

[0145] Step 8: Repeat the above steps until the data extraction of the entire image strip is completed. The extracted data is reassembled in order to form the final DMD display data.

[0146] Step 9: Repeat the same steps to complete the extraction of all image strips.

[0147] Step 10, setting the size of the display window area for each frame on the DMD, that is, the pixel width is W=1920 pixels, and the pixel height is M*(N-1)*Q=756 pixels.

[0148] Step 11, the scanning step of the moving platform in the Y direction is YStep=M×R=4×0.54um=2.16um. A synchronization signal is sent out every time the scanning step YStep is moved to extract an image of the same size as the sliding extraction window in the order of the new graphic strips from bottom to top, and trigger the image to be displayed on the spatial light modulator. At the same time, the laser performs pulse synchronous exposure.

[0149] Step 12, after a new image strip is exposed in the Y direction, the motion platform returns to the bottom and moves a moving step XStep in the X direction, XStep = W × R = 1920 × 0.54 = 1036.8 um, and the next new image strip is exposed in the same manner as step 12 until all new image strips are exposed.

[0150] In this embodiment, for the same row of pixels, three cycles of grayscale extraction are performed on the pixels in the row, and two cycles of grayscale metering exposure are performed during photolithography, that is, the number of grayscale exposure cycles is three times.

[0151] In actual implementation, the values ​​of M, N and Q may also be other values, which are not listed one by one in this embodiment.

[0152] Optionally, the present application further provides a control device, which includes a processor and a memory; the memory stores a program, and the program is loaded and executed by the processor to implement the laser direct writing method provided by the present application.

[0153] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0154] The above-mentioned embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the attached claims.

Claims

1. A laser direct writing method, characterized in that: The method comprises: According to the optical resolution R of the direct writing device, a grayscale image to be processed is obtained; Set the grayscale level N of the lithography, set the scanning pixel step M, and set the number of grayscale exposure cycles Q, so that M*(N-1)*Q is less than or equal to the height of the spatial light modulator display window; Dividing the grayscale image into a plurality of image strips of equal width, wherein the width W of the image strip is less than or equal to the width of the display window of the spatial light modulator; Set the size of the sliding extraction window during exposure; For each of the image strips, grayscale extraction with a sliding extraction window and data reorganization are performed according to the grayscale level N, the scanning pixel step M and the grayscale exposure cycle number Q to obtain a new image strip; After the motion platform completes exposure of a new image strip in the Y direction, it moves a moving step XStep in the X direction, where the moving step XStep is the product of the image strip width W and the optical resolution R, and exposes the next new image strip until the exposure of all new image strips is completed, and the X direction is orthogonal to the Y direction; For each of the image strips, according to the grayscale level N, the scanning pixel step M and the grayscale exposure cycle number Q, a sliding extraction window grayscale extraction and data reorganization are performed to obtain a new image strip, including: Divide the grayscale to obtain N-1 grayscale thresholds, grayscale threshold Gi=i*Gin, 1≤i≤N-1, where Gin is the size of the grayscale interval, Gin=total grayscale number G / grayscale level N; Periodically performing grayscale extraction in sequence from the bottom of the image strip according to the sliding extraction window to obtain binary data, and sequentially placing the binary data into a new image strip from the bottom, the specific steps include: Starting from the bottom of the image strip, grayscale threshold judgment is performed according to the sliding extraction window, data greater than or equal to the first grayscale threshold G1 is set, and data less than the first grayscale threshold G1 is set to zero, to obtain new binary data with a width of W and a height of M*(N-1)*Q; the binary data is placed at the bottom of a new image strip; Control the sliding extraction window to move upward by M pixels to perform grayscale threshold judgment, set the data greater than or equal to the second grayscale threshold G2, and set the data less than the second grayscale threshold G2 to zero, to obtain new binary data with a width of W and a height of *(N-1)*Q; put the binary data into the new image strip in sequence; Repeat N-1 times to complete one cycle of grayscale extraction; The sliding extraction window moves upward by M pixels, and performs the next periodic grayscale extraction until all the current strip data are extracted, and the new image strip is obtained.

2. The method according to claim 1, characterized in that The setting of the size of the sliding extraction window during exposure includes: The height of the sliding extraction window is set to M*(N-1)*Q, and the width is set to the image strip width W.

3. The method according to claim 1, characterized in that Before the grayscale threshold is determined according to the sliding extraction window starting from the bottom of the image strip, the method further includes: M*(N-1)*Q lines of blank data are added to the head of the image strip.

4. The method according to claim 1, characterized in that The step of repeating the above grayscale extraction until all the current strip data is extracted includes: When the end of the image strip does not meet the height of the sliding extraction window, blank data is rounded up to M*(N-1)*Q.

5. The method according to claim 1, characterized in that The set data corresponds to the DMD spatial light modulator being turned on, and the zero data corresponds to the DMD spatial light modulator being turned off.

6. The method according to claim 1, characterized in that The method further comprises: For each of the new image strips, the motion platform is controlled to perform scanning motion in the Y direction, and the scanning step YStep of the motion platform in the Y direction is the product of the scanning pixel step M and the optical resolution R. Every time the scanning step YStep is moved, a synchronization signal is triggered to extract an image with the same size as the sliding extraction window in the order of the new graphic strips from bottom to top, and trigger the spatial light modulator to display the image, while the laser performs pulse synchronous exposure.

7. The method according to any one of claims 1 to 6, characterized in that: The step of obtaining the grayscale image to be processed according to the optical resolution R of the direct writing device includes: The processed image is grayscaled according to the optical resolution R to obtain the grayscale image.

8. A control device, characterized in that: The control device includes a processor and a memory; a program is stored in the memory, and the program is loaded and executed by the processor to implement the laser direct writing method according to any one of claims 1 to 7.

9. A laser direct writing system, characterized in that: The laser direct writing system adopts the laser direct writing method as described in any one of claims 1 to 7.

Images