Automatic control system for maskless photoetching process

Abstract

The invention relates to the technical field of physics and microelectronics, and discloses an automatic control system for a maskless photoetching process, which comprises an acquisition module, a post-processing module, an optical analysis module, an optical system module, a motion monitoring module, an operation control module, a user interaction module and a system packaging and protecting module, the acquisition module provides detailed projection light path element parameters and position details, meanwhile, the optical analysis module adopts a bimodal in-situ monitoring technology and fuses a microscopic imaging system and a projection imaging system, real-time accurate monitoring of an etching position and an exposure condition is achieved, and through light path coupling of a 6500K cold light source and zero photoresist activation risk in the optical system module, the optical system module can accurately monitor the etching position and the exposure condition in real time. The weak contrast of the two-dimensional material is enhanced, a 600nm and ultraviolet coaxial independent low-energy light source pre-projection exposure pattern is introduced, the time cost caused by inaccurate positioning is reduced, a stepping motor and a piezoelectric displacement table closed-loop feedback system are introduced into the motion monitoring module, human interference is avoided, the system can be packaged, and high stability and anti-interference performance are achieved.

Description

Technical Field

[0001] The present invention relates to the fields of physics and microelectronics technology, and specifically to an automated control system for a maskless lithography process. Background Art

[0002] Since the mid-20th century, the third industrial revolution centered around semiconductor technology has profoundly changed the global science and technology and industrial pattern. As the pearl on the crown of modern industry, lithography technology has enabled the number of semiconductor device units to grow in accordance with Moore's law, driving the development of the ultimate processing line width to the 5nm level and becoming the core symbol to measure a country's scientific and technological strength. However, traditional lithography technology relies on a mask to achieve pattern transfer, and its production process has significant drawbacks: the preparation of the mask requires a cycle of 1-2 years, involving high labor, material, and capital costs, and it is difficult to meet the high-efficiency production requirements of the information age. Although the mask technology has formed a stable system, its low efficiency and resource consumption problems have long restricted the further development of the industry, prompting maskless lithography technology to become a research hotspot in the global scientific research and industrial circles.

[0003] Maskless lithography technology mainly includes two types of solutions: laser direct writing and direct projection exposure. Laser direct writing technology directly draws patterns by focusing ultraviolet lasers. Although it has high flexibility, it has strict requirements for system stability, slow direct writing speed, and high economic costs, making it difficult to meet industrialization requirements. Although direct projection exposure technology can theoretically break through the limitation of direct writing efficiency, it is limited by the diffraction limit of traditional projectors and has long been unable to achieve high-precision exposure of micro-nano scale fine patterns. The digital micromirror device (DMD) introduced by Texas Instruments (TI) in 1987 brought a turning point to maskless lithography. Based on MEMS technology, the DMD can achieve dynamic pattern projection and gray-scale control through the spatial light modulation ability of the micromirror array, but its application still faces key challenges: existing technologies lack the ability to real-time monitor the exposure position and etching state. Especially in scenarios such as the processing of two-dimensional material devices that require precise positioning of low-contrast regions (such as electrode deposition and measurement of electrical transport properties), traditional methods are difficult to balance accuracy and cost-effectiveness.

[0004] In summary, although maskless lithography technology has significant advantages in shortening the production cycle and reducing mask dependence, the lack of real-time monitoring ability and cost control problems are still the core technical bottlenecks restricting its wide application, and innovative solutions are urgently needed to break through this limitation. Summary of the Invention

[0005] Technical Problems to be Solved

[0006] In view of the deficiencies of the prior art, the present invention provides an automated control system for a maskless lithography process, which has the advantages of real-time monitoring, precise positioning, low cost and high efficiency, and high imaging quality and stability, and solves the problems of the lack of real-time monitoring ability, difficult cost control and insufficient imaging accuracy in traditional maskless lithography technology.

[0007] Technical solution

[0008] To achieve the above object, the present invention provides the following technical solution: an automated control system for a maskless lithography process, including an acquisition module, a post-processing module, an optical analysis module, an optical system module, a motion monitoring module, an operation control module, a user interaction module, and a system encapsulation and protection module;

[0009] The acquisition module is responsible for acquiring image information, position information, environmental interference information, and light source parameters. The acquisition module includes a CCD image acquisition sub-module, a displacement parameter acquisition sub-module, and an optical parameter acquisition sub-module;

[0010] The post-processing module processes the data acquired by the acquisition module and outputs image pixel coordinates, physical coordinates of the displacement stage, a light source intensity matrix, and environmental parameters;

[0011] The optical analysis module performs pixel-physical quantity conversion, aberration analysis and optimization, and optical transfer function calculation based on the output data of the post-processing module;

[0012] The optical system module is used to optimize the performance of the optical system. The optical system module includes a projection light source sub-module, an optical element sub-module, and an illumination and monitoring sub-module;

[0013] The motion monitoring module is used to drive the displacement stage and optical elements, and to monitor the exposure position and imaging quality of the device in real time;

[0014] The operation control module controls the light source and the software operation interface;

[0015] The user interaction module provides a human-machine interface and simplifies the operation process;

[0016] The system encapsulation and protection module adopts an integrated encapsulation design, and integrally encapsulates the maskless optical system in a customized housing to shield the interference of external stray light.

[0017] Preferably, the CCD image acquisition sub-module captures the field of view image during the lithography process through a CCD detector; the displacement parameter acquisition sub-module uses a 3D piezoelectric displacement stage connected to a translation stage controller that supports closed-loop feedback; the optical parameter acquisition sub-module records and acquires based on the curvature radius and spacing parameters of the lenses in the system during the ZEMAX modeling optimization process.

[0018] Preferably, for the pixel-physical quantity conversion: the image processing and control software running on the PC side converts the pixel coordinates obtained by the user clicking on the target point in the image into the corresponding physical displacement according to the calibrated pixel and spatial distance parameters.

[0019] For the aberration analysis and optimization: the complex relationship between the structural parameters of the optical system and various aberrations is approximated as a set of linear equations by using the mathematical model of automatic optimization of the optical system.

[0020] Preferably, for the calculation of the optical transfer function: based on the principle of Fourier optics, the Fourier transform is performed on the object plane image, and after passing through the imaging system, the image plane image is obtained. The light intensity contrasts K and K' of the object plane and the image plane are calculated respectively. The ratio of the resolution of the corresponding frequencies on the image plane and the object plane is defined as the modulation transfer function, and the phase difference between the corresponding frequencies on the image plane and the object plane is defined as the phase transfer function. The two are collectively referred to as the optical transfer function, and the formula is as follows:

[0021] The definition of the optical transfer function is based on Fourier optics. The image on the object plane is written as:

[0022] I(y) = 1 + a cos(2πvy)

[0023] After passing through the imaging system, the image on the image plane becomes:

[0024] I(y') = 1 + a' cos(2πvy' + θ)

[0025] Then, the light intensity contrasts of the object plane and the image plane are calculated respectively and denoted as K and K'.

[0026]

[0027] The ratio of the resolution of the corresponding frequencies on the image plane and the object plane is denoted as the modulation transfer function:

[0028]

[0029] The phase difference between the corresponding frequencies on the image plane and the object plane is denoted as the phase transfer function:

[0030] PTF(v) = θ v

[0031] The two are collectively referred to as the optical transfer function and are expressed as:

[0032] OTF(v) = MTF(v)e iPTF(v)

[0033] Among them, the higher the image plane contrast, the larger the modulus value of the OTF, indicating the better the imaging quality.

[0034] Preferably, the projection light source sub-module integrates a DMD projector with a positioning light source of weak energy and an exposure light source of strong energy.

[0035] Preferably, the optical element sub-module constructs a coaxial optical system and is configured with a cage cube, a lens fixing bracket with set screws, a stepping motor displacement stage, a vertical optical element fixing bracket, a three-dimensional piezoelectric translation stage, a vertical optical breadboard, a microscope objective, and other optical elements.

[0036] Preferably, the illumination and monitoring sub-module uses a 6500K cold light illumination source to avoid exposing the substrate photoresist during illumination. At the same time, it combines a CCD detector to observe the position of low-contrast samples on the substrate and to monitor the lithography process in real time.

[0037] Preferably, the motion monitoring module includes a 3D piezoelectric displacement stage sub-module and a stepping motor displacement stage sub-module;

[0038] The 3D piezoelectric displacement stage sub-module is used to move the substrate to be exposed to the required position and height, and accurately move the substrate in three degrees of freedom directions according to the displacement command calculated by the data analysis module.

[0039] The stepping motor displacement stage sub-module is connected to the lens fixing bracket with set screws and coaxially moves the lens position through the stepping motor-controlled displacement module.

[0040] Preferably, in the operation control module, the light source control: controls the on / off of the red light source, blue light source, and white light illumination source of the DMD optical engine, and turns on or off the corresponding light source according to different stages of the lithography process;

[0041] The software operation interface in the operation control module: is a control software running on the PC side, provides a user operation interface, and the user imports the pattern to be exposed, sets the blue light exposure intensity and exposure time, and clicks to select the position of the negative film to be exposed on the interface.

[0042] Preferably, the interaction process of the user interaction module:

[0043] S2.1. Pattern import and preview: The PC software loads the design pattern, and the red light is pre-projected onto the substrate;

[0044] S2.2. One-key calibration: The user clicks on the target position in the CCD image, and the system automatically calculates the displacement amount and drives the piezoelectric displacement stage;

[0045] S2.3. Exposure execution: Set the blue light parameters, and the program automatically switches the light source and triggers the exposure;

[0046] S2.4. Result display: Visualize the developed image and the MTF analysis result;

[0047] S2.5, Output Interface: Real-time image display, stage coordinates, OTF curve, and exposure progress bar.

[0048] Compared with the prior art, the present invention provides an automated control system for a maskless lithography process, which has the following beneficial effects:

[0049] 1. By constructing an acquisition module, a post-processing module, an optical analysis module, an optical system module, a motion monitoring module, an operation control module, a user interaction module, and a system encapsulation and protection module, the modules cooperate closely to achieve a maskless lithography process, realizing full-process automation from data acquisition, analysis, optical operation to motion control and process execution. The acquisition module provides detailed parameters and position details of the projection optical path components. At the same time, the optical analysis module uses a dual-modal in-situ monitoring technology, integrating a microscopic and a projection imaging system, to achieve real-time and accurate monitoring of the etching position and exposure conditions. By coupling a 6500K cold light source and zero photoresist activation risk in the optical system module, the weak contrast of two-dimensional materials is enhanced, and a 600nm and ultraviolet coaxial independent low-energy light source is introduced to pre-project the exposure pattern, reducing the time cost caused by inaccurate positioning. A closed-loop feedback system of a stepper motor and a piezoelectric stage is introduced in the motion monitoring module to avoid human interference. The system encapsulation and protection module encapsulates the whole process, making the system have the advantages of real-time monitoring and accurate positioning, low cost and high efficiency, high imaging quality and stability, and solving the problems of the lack of real-time monitoring ability, difficult cost control, and insufficient imaging accuracy in traditional maskless lithography technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 It is a schematic diagram of the basic structure of the DMD projection optical engine of the present invention;

[0051] Figure 2 It is a specific design optical path diagram of the visible light illumination source and the CCD detector of the present invention;

[0052] Figure 3 It is a 3D modeling diagram of the maskless lithography machine system of the present invention;

[0053] Figure 4 It is an optical transfer function diagram of the present invention;

[0054] Figure 5 It is an axial aberration diagram of the present invention;

[0055] Figure 6 It is a spherical aberration diagram of the present invention;

[0056] Figure 7 It is a processing test result diagram of the present invention;

[0057] Figure 8 It is a schematic diagram of the principle of using the maskless lithography machine of the present invention; DETAILED DESCRIPTION OF THE INVENTION

[0058] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0059] Please refer to Figures 1 - 8 , an automated control system for a maskless lithography process, including an acquisition module, a post-processing module, an optical analysis module, an optical system module, a motion monitoring module, an operation control module, a user interaction module, and a system encapsulation and protection module;

[0060] The acquisition module is responsible for acquiring image information, position information, environmental interference information, and light source parameters. The acquisition module includes a CCD image acquisition sub-module, a displacement parameter acquisition sub-module, and an optical parameter acquisition sub-module;

[0061] The post-processing module processes the data acquired by the acquisition module and outputs image pixel coordinates, displacement stage physical coordinates, light source intensity matrix, and environmental parameters;

[0062] The optical analysis module performs pixel-physical quantity conversion, aberration analysis and optimization, and optical transfer function calculation based on the output data of the post-processing module;

[0063] The optical system module is used to optimize the performance of the optical system, reduce the influence of aberration and chromatic dispersion. The optical system module includes a projection light source sub-module, an optical element sub-module, and an illumination and monitoring sub-module;

[0064] The motion monitoring module is used to drive the displacement stage and optical elements to achieve high-precision positioning and dynamic adjustment, and to monitor the exposure position and imaging quality of the device in real time to ensure the accuracy of the exposure position and the stability of the imaging quality;

[0065] The operation control module controls the light source and the software operation interface;

[0066] The user interaction module provides a man-machine interface to simplify the operation process;

[0067] The system encapsulation and protection module adopts an integrated encapsulation design, integrally encapsulates the maskless optical system in a customized shell, shields the interference of external stray light, isolates the intrusion of external dust particles through a multi-layer sealing structure, ensures that the optical elements maintain high light transmittance and low scattering loss for a long time, and improves the environmental adaptability, reliability, and durability of the system;

[0068] The advantages are as follows: The automated control system of the present invention achieves beneficial effects through multi-dimensional innovative design. At the control level, high-precision sensors and closed-loop control algorithms are introduced to completely eliminate the optical path deviation caused by manual operation, effectively improving the stability and repeatability of the optical system and ensuring the accuracy of the lithography process. In terms of structural design, an integrated packaging technology is adopted to encapsulate the maskless optical system in a customized shell. With a sealed structure, external stray light and dust particles are isolated, ensuring high light transmittance and low scattering loss of the optical components, and enhancing the environmental adaptability of the system. In terms of function implementation, each module operates closely in coordination to achieve the maskless lithography process, realizing full-process automation from data acquisition, analysis, optical operation to motion control and process execution. This not only improves production efficiency but also provides reliable physical protection for high-precision optical applications, greatly enhancing the reliability and durability of the system and meeting diverse high-precision lithography requirements.

[0069] The projection light source sub-module integrates DMD projector systems with two frequency bands, namely a positioning light source with a wavelength of 600nm with relatively weak energy and an exposure light source with a wavelength of 406nm with relatively strong energy, to achieve the projection of red light projection patterns and blue light exposure patterns. The basic structural schematic of the DMD projection optical engine Figure 1 。

[0070] The optical element sub-module constructs a 30mm coaxial optical system, configured with two 30mm cage cubes, 5 top screw type lens fixing brackets, two stepper motor displacement stages, several vertical optical element fixing brackets, a three-dimensional piezoelectric translation stage (stacked by two horizontal displacement stages and one vertical displacement stage), a vertical optical breadboard, a microscope objective lens and other optical elements to ensure system stability and eliminate off-axis aberrations and achieve precise imaging.

[0071] The illumination and monitoring sub-module uses a visible light illumination source (6500K cold light illumination source), which avoids exposing the substrate photoresist during illumination. At the same time, combined with a CCD detector, it realizes the observation of the position of low-contrast samples on the substrate and the real-time monitoring of the lithography process. The specific designed optical path diagrams of the visible light illumination source and the CCD detector are as Figure 2 。

[0072] Among them, the lithography light source is an integrated DMD projection optical engine with two bands. In actual optical design, issues such as imaging quality and pattern magnification need to be considered. The basic 3D modeling design of the actual system is carried out using SolidWorks as Figure 3 (Shown in the 3D modeling diagram of the maskless lithography machine system):

[0073] The motion monitoring module includes a three-dimensional piezoelectric displacement stage sub-module and a stepper motor displacement stage sub-module;

[0074] The 3D piezoelectric displacement stage sub-module is used to move the substrate to be exposed to the required position and height, and accurately move the substrate in the three degrees of freedom directions according to the displacement instructions calculated by the data analysis module. The control process is as follows:

[0075] S1.1. Use a CCD to capture the field of view image and fix the pixels;

[0076] S1.2. The 3D piezoelectric displacement stage is connected to a translation stage controller that supports closed-loop feedback;

[0077] S1.3. Run image processing and control software on the PC side;

[0078] S1.4. Calibrate the parameters of pixels and spatial distances;

[0079] S1.5. The user clicks on the target point in the image to obtain its pixel coordinates;

[0080] S1.6. Calculate the offset (pixels) between the target point and the center of the field of view;

[0081] S1.7. Convert it to a physical displacement (μm);

[0082] S1.8. Send instructions to drive the translation stage to move so that the target point moves to the center of the field of view.

[0083] The stepping motor displacement stage sub-module is connected to the setscrew fixing bracket and moves the lens position coaxially through the stepping motor control displacement module to meet the best imaging requirements, and cooperates with the 3D piezoelectric displacement stage to achieve precise adjustment of the optical path.

[0084] Light source control in the operation control module: Realize the on / off control of the red light source, blue light source and white light illumination source of the DMD optical engine, and turn on or off the corresponding light source according to different stages of the lithography process;

[0085] Software operation interface in the operation control module: The control software running on the PC side provides a user operation interface. The user can import the pattern to be exposed, set the blue light exposure intensity and exposure time, click to select the position of the negative film to be exposed, etc. on the interface to realize the control of the entire lithography process.

[0086] Interaction process of the user interaction module:

[0087] S2.1. Pattern import and preview: The PC software loads the designed pattern and projects it onto the substrate in red light for preview;

[0088] S2.2. One-key calibration: The user clicks on the target position in the CCD image, and the system automatically calculates the displacement and drives the piezoelectric displacement stage;

[0089] S2.3. Exposure execution: Set the blue light parameters, and the program automatically switches the light source and triggers the exposure;

[0090] S2.4, Result display: The developed image ( Figure 7 ) and the visualization display of the MTF analysis results;

[0091] S2.5, Output interface: Real-time image display, displacement stage coordinates, OTF curve, exposure progress bar.

[0092] The CCD image acquisition sub-module captures the field of view image during the lithography process through a CCD detector, which is used to monitor the imaging of the projection pattern on the substrate and the substrate surface state information. After fixing the pixels, the image data is transmitted to the post-processing module (for example, when adjusting the height of the 3D piezoelectric displacement stage to make the projection image clearly imaged, the CCD captures images in real time for subsequent analysis); the displacement parameter acquisition sub-module uses a 3D piezoelectric displacement stage connected to a translation stage controller that supports closed-loop feedback to collect the actual displacement parameters of the displacement stage in three degrees of freedom directions (x, y, z), and feeds them back to the operation control module to achieve precise displacement control; the optical parameter acquisition sub-module records and collects based on the curvature radius and spacing parameters of the lenses in the system during the ZEMAX modeling optimization process, providing basic data for the analysis and optimization of the optical system. At the same time, data such as the light intensity contrast between the object plane and the image plane involved in the calculation of the optical transfer function is also collected in this sub-module.

[0093] Based on the output data of the post-processing module, the optical analysis module performs pixel-physical quantity conversion, aberration analysis and optimization, and optical transfer function calculation. Specifically:

[0094] 1. Pixel-physical quantity conversion: The image processing and control software running on the PC converts the pixel coordinates obtained by the user clicking on the target point in the image into the corresponding physical displacement (μm) according to the calibrated pixel and spatial distance parameters. Its principle is based on the analysis of the geometric relationship and optical characteristics of the imaging system, and the coordinate conversion is achieved by establishing a mathematical model;

[0095] 2. Aberration analysis and optimization: Using the mathematical model of automatic optimization of the optical system, the complex relationship between the structural parameters of the optical system (such as curvature radius, lens spacing, and material refractive index) and various aberrations (spherical aberration, chromatic aberration, astigmatism, field curvature) is approximated as a set of linear equations. By introducing weight coefficients to quantify the influence of different aberrations and combining constraint conditions (such as lens size, material characteristics), numerical optimization algorithms (such as gradient descent method or genetic algorithm) are used to solve the global minimum of the aberration within the parameter value range to optimize the imaging quality of the optical system. Finally, this model can output a set of optimal structural parameter combinations on the premise of meeting engineering constraints, thereby achieving the improvement of imaging quality. The various lens parameters are optimized through ZEMAX modeling, and the configuration and parameter table are shown in Table 1:

[0096] Table 1: Lens Structure and Position Parameter Table of Maskless Lithography Imaging System

[0097]

[0098]

[0099] When the optical system is optimized to a better degree, its optical transfer function can be calculated.

[0100] 3. Calculation of Optical Transfer Function: Based on the principle of Fourier optics, the Fourier transform is performed on the object plane image. After passing through the imaging system, the image plane image is obtained. The light intensity contrasts K and K' of the object plane and the image plane are calculated respectively. The ratio of the resolution of the corresponding frequencies on the image plane and the object plane is defined as the modulation transfer function (MTF), and the phase difference between the corresponding frequencies on the image plane and the object plane is defined as the phase transfer function (PTF). The two are collectively referred to as the optical transfer function (OTF), and the formula is as follows:

[0101] (1) The definition of the optical transfer function is based on Fourier optics. The image on the object plane is written as (frequency components) through Fourier transform:

[0102] I(y) = 1 + a cos(2πvy)

[0103] (2) After passing through the imaging system, the image on the image plane becomes:

[0104] I(y) = 1 + a' cos(2πvy' + θ)

[0105] (3) Then, the light intensity contrasts of the object plane and the image plane are calculated respectively and denoted as K and K'.

[0106]

[0107] (4) The ratio of the resolution of the corresponding frequencies on the image plane and the object plane is denoted as the modulation transfer function (Modulation Transfer Function, MTF):

[0108]

[0109] (5) The phase difference between the corresponding frequencies on the image plane and the object plane is denoted as the phase transfer function (Phase Transfer Function, PTF):

[0110] PTF(v) = θ v

[0111] (6) The two are collectively referred to as the optical transfer function (Optics Transfer Function OTF) and are expressed as:

[0112] OTF(v) = MTF(v)e iPTF(v)

[0113] Among them, the higher the object plane contrast, the larger the modulus value of OTF, indicating better imaging quality. Due to the limitation of the diffraction limit, when the spatial frequency ν of the object plane image is too large, it cannot be resolved on the image plane. In terms of the optical transfer function, the modulus value of OTF is 0, and this point is called the cut-off frequency of the imaging system. This is a limitation on imaging quality based on physical principles and cannot make the cut-off frequency reach infinity by optimizing the optical system. Therefore, the optical imaging system is equivalent to a low-pass filter;

[0114] The advantages are: evaluating the performance of the imaging system by calculating OTF. The higher the image plane contrast (i.e., the larger the modulus value of OTF), the better the imaging quality, and the cut-off frequency of the system is determined.

[0115] Under the condition of limited budget, a standard plano-convex lens with a lower purchase cost is purchased, that is, without adding conical curvature correction. Only by adjusting the lens position, the optimized optical transfer function of the system is as Figure 4 (Optical transfer function diagram);

[0116] From the Figure 3 above, its spatial cut-off frequency almost coincides with the diffraction limit cut-off frequency, and the OTFs of the meridional plane and the sagittal plane coincide. This is because in an ideal situation, there are no off-axis aberrations in a coaxial system. For further optimization, surface correction needs to be added, and finally, it can be achieved that the modulus value curve of the system OTF almost coincides with the diffraction limit;

[0117] During use, due to material dispersion, it cannot be determined whether the image plane positions of the red light projection pattern and the blue light exposure pattern are on the same plane. At this time, the chromatic aberration curve of the system can provide a reference, such as Figure 5 (Axial aberration diagram)- Figure 6 (Spherical aberration diagram) shows:

[0118] From the Figure 5 it can be seen that the optical imaging system designed by the present invention can achieve the purpose of achromatism. From the Figure 6 it is found that the image plane distance between red light and blue light is within 5 microns. After the red light projection is clear, the 3D piezoelectric displacement stage Scanner z can be moved forward by a fixed distance (depending on the actual optical system) to accurately project the blue light onto the image plane. After preliminary experimental verification, the image after exposure and development is as Figure 7 (Processing test result diagram) shows;

[0119] The advantages are as follows: The automated control system adopted in the present invention not only has an intuitive human-machine interaction interface to ensure a simple and efficient operation process, but also realizes sub-micron-level stability control through a high-precision closed-loop control algorithm and a real-time feedback adjustment mechanism. After being optimized by modular design, the sensitivity of the system to the use environment is reduced. Especially after encapsulation, the multi-layer sealing structure effectively isolates the intrusion of external stray light and micron-sized dust particles. This design can not only meet the strict requirements of the optical system for environmental cleanliness, but also enhance the reliability of the system under extreme working conditions through vibration isolation and temperature and humidity compensation technologies, providing an ideal solution for industrial-grade optical instruments and precision measurement equipment.

[0120] After the system is built according to the above scheme, the specific usage process is as follows:

[0121] T1. Place a substrate with a relatively high reflectivity (such as a single crystal silicon wafer) on the 3D piezoelectric displacement stage, turn on the red light source of the DMD optical engine, import the pattern to be exposed, project the image onto the substrate, and then adjust the height of the 3D piezoelectric displacement stage and fine-tune it through the stepper motorized displacement module. Figure 3 Fix the support bracket with the 2-5 set screws in the middle, so that the projected image on the negative film can be clearly imaged at the center of the CCD negative film. The PC-side program automatically reads the height h1 of the piezoelectric displacement platform in the z direction at this time.

[0122] T2. Turn off the red light source and turn on the blue light source. It is found that the pattern captured in the CCD becomes blurred. Adjust the height of the 3D piezoelectric displacement stage until the blue light pattern on the negative film captured in the CCD becomes clear. The PC-side program automatically reads the height h2 of the piezoelectric displacement platform in the z direction at this time, and the program automatically locks: H = h1 - h2.

[0123] T3. Turn off the optical engine and turn on the white light illumination source. Place the substrate coated with photoresist on the 3D piezoelectric displacement stage and adjust the height of the 3D piezoelectric displacement stage so that the substrate can be clearly imaged on the CCD.

[0124] T4. Open the CCD image read on the PC-side control software, click the position of the negative film to be exposed with the mouse, and the piezoelectric displacement stage automatically translates the position to the center of the field of view through closed-loop feedback and stabilizes it.

[0125] T5. Turn on the red light source of the optical engine, import the pattern to be exposed, and it is found that the exposed pattern falls on the position to be exposed and can be clearly imaged at the center of the CCD.

[0126] T6. Turn off the red light source. At this time, the program automatically translates the 3D piezoelectric displacement stage upward by a height of H in the z direction to reach the blue light projection image plane. The user sets the blue light exposure intensity and exposure time on the PC side.

[0127] T7. Turn on the blue light, expose the substrate, and take out the substrate after the exposure is completed.

[0128] Develop the substrate, and the desired etching pattern can be obtained at the desired etching position. For the schematic diagram of the use of the maskless lithography machine, please refer to Figure 8 .

[0129] The present invention has many beneficial effects, specifically: in the construction of the optical system, the acquisition module provides detailed parameters and position details of the projection optical path components. After comprehensive image quality evaluation, a high-quality optical system is built or further optimized according to the acquired data; at the monitoring technology level, a dual-modal in-situ monitoring technology is adopted, innovatively integrating a microscopic and a projection imaging system to achieve real-time and accurate monitoring of the etching position and exposure conditions; in the application of two-dimensional material processing, the optical path is coupled with a 6500K cold light source system, with zero risk of photoresist activation, enhancing the weak contrast of two-dimensional materials, and enabling the observation of the positions of low-contrast samples on the substrate at low cost, which is conveniently applied to the research on the transport properties of two-dimensional materials; for lithography positioning, a 600nm and ultraviolet coaxial independent low-energy light source is introduced to pre-project the exposure pattern, effectively reducing the time cost caused by inaccurate positioning; in the selection of optical components and the construction of the system, the parameters of the used spherical plano-convex lens are common and the cost is low. After experimental verification, it has strong practicability and is easy to build; in terms of optical path adjustment and system stability, a closed-loop feedback system of a stepper motor and a piezoelectric displacement stage is introduced to avoid human interference, and the system can be packaged, with excellent stability and anti-interference ability.

[0130] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it is understood that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. An automated control system for a maskless lithography process, characterized in that, It includes a collection module, a post-processing module, an optical analysis module, an optical system module, a motion monitoring module, an operation control module, a user interaction module, and a system encapsulation and protection module; The collection module is responsible for collecting image information, position information, environmental interference information, and light source parameters. The collection module includes a CCD image collection sub-module, a displacement parameter collection sub-module, and an optical parameter collection sub-module; The post-processing module processes the data collected by the collection module and outputs image pixel coordinates, physical coordinates of the displacement stage, light source intensity matrix, and environmental parameters; Based on the output data of the post-processing module, the optical analysis module performs pixel-physical quantity conversion, aberration analysis and optimization, and optical transfer function calculation; The optical system module is used to optimize the performance of the optical system. The optical system module includes a projection light source sub-module, an optical element sub-module, and an illumination and monitoring sub-module; The motion monitoring module is used to drive the displacement stage and optical elements, and to monitor the exposure position and imaging quality of the device in real time; The operation control module controls the light source and the software operation interface; The user interaction module provides a human-machine interface and simplifies the operation process; The system encapsulation and protection module adopts an integrated encapsulation design, and integrally encapsulates the maskless optical system in a customized shell to shield the interference of external stray light.

2. The automated control system of a maskless lithography process according to claim 1, characterized in that: The CCD image collection sub-module captures the field of view image during the lithography process through a CCD detector; the displacement parameter collection sub-module uses a 3D piezoelectric displacement stage connected to a translation stage controller that supports closed-loop feedback; During the ZEMAX modeling and optimization process, the optical parameter collection sub-module records and collects based on the curvature radius and spacing parameters of the lenses in the system.

3. The automated control system for a maskless lithography process according to claim 1, characterized in that: The pixel-physical quantity conversion: The image processing and control software running on the PC, according to the calibrated pixel and spatial distance parameters, converts the pixel coordinates obtained by the user clicking on the target point in the image into the corresponding physical displacement; The aberration analysis and optimization: Using the mathematical model of automatic optimization of the optical system, the complex relationship between the structural parameters of the optical system and various aberrations is approximated as a set of linear equations.

4. The automated control system of a maskless lithography process according to claim 1, wherein: The optical transfer function calculation: Based on the Fourier optical principle, perform Fourier transform on the object plane image, and obtain the image plane image after passing through the imaging system. Calculate the light intensity contrast ratios K and K' of the object plane and the image plane respectively. Define the ratio of the resolutions of the corresponding frequencies on the image plane and the object plane as the modulation transfer function, and define the phase difference between the corresponding frequencies on the image plane and the object plane as the phase transfer function. The two are collectively referred to as the optical transfer function. The formula is as follows: The definition of the optical transfer function is based on Fourier optics. The image on the object plane is written as: I(y) = 1 + a cos(2πvy) After passing through the imaging system, the image on the image plane becomes: I(y') = 1 + a' cos(2πνy' + θ) Then calculate the light intensity contrast ratios of the object plane and the image plane respectively, denoted as K and K'; Denote the ratio of the resolutions of the corresponding frequencies on the image plane and the object plane as the modulation transfer function: Denote the phase difference between the corresponding frequencies on the image plane and the object plane as the phase transfer function: PTF(ν) = θ ν Both are collectively referred to as the optical transfer function, which is expressed as: OTF(v) = MTF(v)e iPTF(v) Among them, the higher the image plane contrast, the larger the modulus value of the 0TF, indicating better imaging quality.

5. The automated control system for a maskless lithography process according to claim 1, wherein: The projection light source sub-module integrates a DMD projector with a positioning light source of weak energy and an exposure light source of strong energy.

6. The automated control system of a maskless lithography process according to claim 1, characterized in that: The optical element sub-module constructs a coaxial optical system, configured with a cage cube, a lens fixing bracket with set screws, a stepping motor displacement stage, a vertical optical element fixing bracket, a three-dimensional piezoelectric translation stage, a vertical optical breadboard, a microscope objective, and other optical elements.

7. The automated control system of a maskless lithography process according to claim 1, characterized in that: The illumination and monitoring sub-module uses a 6500K cold light illumination source to avoid exposing the substrate photoresist during the illumination process. At the same time, it combines a CCD detector to observe the position of low-contrast samples on the substrate and monitor the lithography process in real time.

8. The automated control system for a maskless lithography process according to claim 1, characterized in that: The motion monitoring module includes a 3D piezoelectric displacement stage sub-module and a stepping motor displacement stage sub-module; The 3D piezoelectric displacement stage sub-module is used to move the substrate to be exposed to the required position and height, and accurately move the substrate in three degrees of freedom directions according to the displacement command calculated by the data analysis module. The stepping motor displacement stage sub-module is connected to the set screw fixing bracket and coaxially moves the lens position through the stepping electric control displacement module.

9. The automated control system for a maskless lithography process according to claim 1, characterized in that: In the operation control module, the light source control: controls the on / off of the red light source, blue light source, and white light illumination source of the DMD optical engine, and turns on or off the corresponding light source according to different stages of the lithography process; In the operation control module, the software operation interface: a control software running on the PC side provides a user operation interface. The user imports the pattern to be exposed, sets the blue light exposure intensity and exposure time, and clicks to select the position of the negative film to be exposed on the interface.

10. The automated control system for a maskless lithography process according to claim 1, characterized in that: The interaction process of the user interaction module: S2.

1. Pattern import and preview: The PC software loads the design pattern, and the red light is pre-projected onto the substrate; S2.

2. One-key calibration: The user clicks on the target position in the CCD image, and the system automatically calculates the displacement amount and drives the piezoelectric displacement stage; S2.

3. Exposure execution: Set the blue light parameters, and the program automatically switches the light source and triggers the exposure; S2.

4. Result display: Visual display of the developed image and MTF analysis results; S2.

5. Output interface: Real-time image display, displacement stage coordinates, OTF curve, and exposure progress bar.

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