A photolithography method, system and computer storage medium
By employing gradient dose exposure, dynamic focus scanning exposure, spectral optimization exposure, auxiliary layer exposure enhancement, and development synergistic exposure, the energy distribution inside thick photoresist was controlled, solving the problem of insufficient bottom exposure, achieving uniform exposure and thorough development, and avoiding top overexposure and sidewall erosion.
Patent Information
- Application Number
- CN202610651128.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-05-12
- Publication Date
- 2026-06-12
Smart Images
Figure CN122194586A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of photolithography, and more specifically, to a photolithography method, system, and computer storage medium. Background Technology
[0002] In the photolithography process of thick photoresist layers (thickness greater than 10 μm, even tens to hundreds of micrometers), the absorption and diffraction effects of light within the photoresist often lead to insufficient exposure at the bottom of the layer, resulting in incomplete photochemical reactions. This can cause problems such as bottom residue after development, rough sidewalls, bottom linewidth greater than top (inverted trapezoidal structure), or even no opening at the bottom. Traditional solutions include increasing the exposure dose, extending the development time, using special developers, or multilayer photoresist processes. However, these methods often come with drawbacks such as top overexposure, pattern sidewall erosion, process complexity, and increased costs.
[0003] Therefore, there is an urgent need for a photolithography method and system that can effectively improve the uniformity of exposure and thorough development of the bottom of thick resist without significantly increasing process complexity or damaging the top contour of the pattern. Summary of the Invention
[0004] The technical problem to be solved by the embodiments of this application is that in thick-layer photoresist lithography, insufficient exposure at the bottom can easily lead to development defects. Traditional solutions will result in overexposure at the top, sidewall erosion, and increased process costs.
[0005] To address the aforementioned technical problems, this application provides a photolithography method, employing the following technical solution: A photolithography method, comprising: Control the initialization of the lithography system; Select an exposure method and use the exposure method to adjust the energy distribution inside the photoresist so that the bottom of the photoresist reaches the specified exposure state; The exposure method includes one or more of the following: gradient dose exposure method, dynamic focus scanning exposure method, spectral optimization exposure method, auxiliary layer exposure enhancement method, and development synergistic exposure method; The photolithography process is completed through development.
[0006] Furthermore, the gradient dose exposure method includes: dynamically adjusting the exposure dose during a single or step-by-step exposure process, with the exposure dose increasing in a gradient from the top to the bottom of the photoresist.
[0007] Furthermore, the stepwise increase in exposure dose from the top to the bottom of the photoresist includes: firstly, performing top patterning exposure of the photoresist with the first dose, wherein the first dose is 70%-90% of the dose required for the complete formation of the top pattern of the photoresist; The lower middle portion of the photoresist is then subjected to enhanced exposure using the second dose, which is 150%-300% of the first dose.
[0008] Furthermore, the dynamic focus scanning exposure method includes the following steps: dynamically adjusting the position of the focal plane of the exposure operation in the photolithography system, so that the focal plane is scanned stepwise or continuously along the thickness direction of the photoresist, and allocating the dwell time of the focal plane at different positions according to the thickness of the photoresist and the pattern requirements to control the local exposure dose. The dynamic adjustment of the focal plane position for exposure operations in the photolithography system includes: The photolithography system's moving stage is moved longitudinally, causing the photoresist to sequentially enter the focal plane at different depths; and / or, Adjust the adjustable lens group of the photolithography system to change the position of the focal plane of the photolithography system.
[0009] Furthermore, the spectral optimization exposure method includes the following steps: exposing the photoresist from top to bottom using multiple specified wavelengths of light with gradually increasing penetrating power; The process of forming multiple specified wavelengths of light is as follows: multiple original wavelengths of light are provided by a broadband light source, and the desired specified wavelength of light is selected or combined from the original wavelengths of light by a filtering system.
[0010] Further, the auxiliary layer exposure enhancement method includes the following steps: coating an auxiliary layer on the substrate, the auxiliary layer being located below the photoresist, n 辅助层 =(n 光刻胶 *n 基底 )^0.5, where n is the refractive index.
[0011] Further, the development-co-exposure method includes: during the exposure stage, controlling the edge exposure amount at the bottom of the patterned sidewalls of the photoresist through spatially selective dose control to form a modified resist layer region; the control of the edge exposure amount at the bottom of the patterned sidewalls of the photoresist through spatially selective dose control includes: adding sub-resolution auxiliary patterns around the main pattern on the mask, and using diffraction or scattering effects to add additional exposure at the bottom of the sidewalls; and / or, After the main body of the photoresist is exposed, a global exposure operation or a thermal baking operation is introduced to promote the reaction of photosensitive components in the bottom residue of the photoresist. Wherein, the wavelength of the global exposure is not less than the wavelength of the subject exposure, the dose of the global exposure is 10%-50% of the dose of the subject exposure, and the time of the global exposure is 1-10s; The baking temperature is 80-120℃, and the time is 60-300s.
[0012] To address the aforementioned technical problems, this application also provides a photolithography system, comprising a control device and a dose and timing control unit electrically connected to the control device; the dose and timing control unit includes a dynamic focusing device and a dose modulation device, both of which are electrically connected to and controlled by the control device; wherein... A control device for generating control commands based on the thickness of the photoresist and the target pattern; A dynamic focusing device includes a movable workpiece stage and an adjustable lens group. The dynamic focusing device uses the movable workpiece stage and the adjustable lens group to position and scan the focal plane in the thickness direction of the photoresist. A dose modulation device is used in conjunction with the dynamic focusing device to control the exposure energy of the photoresist.
[0013] Furthermore, the dose modulation device is used to adjust the light intensity; and / or, The dose modulation device performs time integration using a spatial light modulator pattern to deliver a local dose to the photoresist.
[0014] To address the aforementioned technical problems, this application also provides a computer-readable storage medium storing computer-readable instructions, which, when executed by a processor, implement the steps of the aforementioned photolithography method.
[0015] Compared with the prior art, the embodiments of this application have the following main advantages: This application utilizes one or more of the following methods to regulate the internal energy distribution of photoresist: gradient dose exposure, dynamic focus scanning exposure, spectral optimization exposure, auxiliary layer exposure enhancement, and development synergistic exposure. This allows the bottom of a thick photoresist layer to receive sufficient and uniform exposure without significantly increasing process complexity or damaging the top contour of the pattern. This effectively reduces bottom residue, sidewall roughness, and inverted trapezoidal structure after development, while also reducing top overexposure, sidewall erosion, and cost increases. Attached Figure Description
[0016] To more clearly illustrate the solutions in this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.
[0017] Figure 1 This is a schematic diagram of the structure of the photolithography system in the embodiments of this application.
[0018] Figure 2This is a schematic flowchart of the photolithography method in the embodiments of this application.
[0019] Figure 3 This is an SEM image of the photoresist obtained in Example 1 of the photolithography method.
[0020] Figure 4 This is a SEM image of the photoresist obtained in Comparative Example 1 using the photolithography method.
[0021] Reference numerals: 1. Control device; 2. Dosage and timing control unit; 21. Dynamic focusing device; 22. Dosage modulation device; 3. Developing device. Detailed Implementation
[0022] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terminology used herein in the specification of the application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application; the terms "comprising" and "having," and any variations thereof, in the specification, claims, and foregoing drawings of this application are intended to cover non-exclusive inclusion. The terms "first," "second," etc., in the specification, claims, or foregoing drawings of this application are used to distinguish different objects, not to describe a particular order.
[0023] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.
[0024] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings.
[0025] A photolithography method includes the following steps: Control the initialization of the lithography system; Select an exposure method and adjust the energy distribution inside the photoresist to make the bottom of the photoresist reach a specified exposure state, wherein the specified exposure state is to obtain sufficient and uniform exposure; The exposure method includes one or more of the following: gradient dose exposure method, dynamic focus scanning exposure method, spectral optimization exposure method, auxiliary layer exposure enhancement method, and development synergistic exposure method; The photolithography process is completed through development.
[0026] By employing one or more of the following methods—gradient dose exposure, dynamic focus scanning exposure, spectral optimization exposure, auxiliary layer exposure enhancement, and development synergistic exposure—the energy distribution inside the photoresist can be controlled, ensuring sufficient and uniform exposure dose at the bottom of the photoresist layer. This effectively avoids problems such as bottom residue and lack of opening at the bottom after development, thus improving the uniformity of bottom exposure and thorough development of thick photoresist.
[0027] In addition, unlike traditional methods that simply increase the overall exposure dose, this method enhances the bottom exposure without significantly increasing the top exposure dose by finely controlling the energy distribution (such as gradient dose, focus scanning, spectral optimization, etc.), thus making it less likely to cause overexposure or distortion of the top outline of the image.
[0028] Because the bottom is fully exposed and the energy distribution is more uniform, the sidewalls of the developed film are steeper and smoother, which can effectively eliminate the "inverted trapezoidal structure" (bottom line width is greater than top) and rough sidewalls caused by insufficient bottom dose.
[0029] The exposure method used can be achieved on existing photolithography equipment by adjusting the exposure strategy (such as dose gradient, focus scanning, spectral selection, etc.), without the need to introduce complex multilayer photoresist processes or special developing solutions, thus avoiding significant changes to the existing process flow.
[0030] Among them, gradient dose exposure method: is often used in scenarios with a photoresist thickness of 10-50um, a medium photoresist absorption coefficient (such as i-line photoresist), and a relatively wide top pattern line (>2μm); Dynamic focus scanning exposure method: commonly used in scenarios with adhesive thickness of 30~200um, deep holes, trenches and other high aspect ratio structures; Spectral optimization exposure method: It is often used in scenarios where the photoresist thickness is 20~100μm and the photoresist has a broad spectrum response (such as AZ series, SU-8), and it is necessary to take into account both small features at the top and large openings at the bottom. Auxiliary layer exposure enhancement method: Commonly used in scenarios where the resist thickness is >30μm, the substrate has strong reflection (such as silicon or metal), and it is necessary to eliminate the bottom "foot" or "root" phenomenon; it works best in combination with the spectral optimization method; Developing and exposure method: often used in scenarios with narrow process windows and large fluctuations in resist thickness.
[0031] This application organically combines various energy control techniques, such as gradient dose exposure, dynamic focus scanning exposure, spectral optimization exposure, auxiliary layer exposure enhancement, and development-assisted exposure, according to the physical requirements of thick resist lithography. For example, gradient dose exposure compensates for light absorption attenuation, and dynamic focus scanning exposure corrects defocus blur; the coupling of the two can achieve clear and uniform energy exposure of thick resist. Furthermore, the auxiliary layer exposure enhancement method is added, utilizing its reflection / fluorescence effect to enhance the long-wavelength energy at the bottom. Finally, the global exposure or thermal baking coordinated by the development-assisted exposure method serves as a "safety net," helping to completely eliminate residue at the bottom.
[0032] By optimizing the energy distribution within the adhesive layer through the exposure method itself, ideal pattern transfer effects can be obtained through conventional development processes without excessively extending the development time or using highly corrosive special developers, thereby reducing the risk of sidewall erosion.
[0033] By avoiding multi-layer photoresist processes, special materials, or additional auxiliary equipment, the problem of insufficient bottom exposure in thick photoresist lithography can be solved without significantly increasing manufacturing costs, resulting in good economic efficiency and mass production feasibility.
[0034] Furthermore, the gradient dose exposure method includes: dynamically adjusting the exposure dose during a single or step-by-step exposure process, with the exposure dose increasing in a gradient from the top to the bottom of the photoresist.
[0035] By increasing the exposure dose from top to bottom along the photoresist thickness direction, the absorption attenuation of light during propagation in the photoresist layer is compensated, resulting in higher actual deposition energy at the bottom of the photoresist layer than at the top. This helps to ensure sufficient photochemical reaction at the bottom without significantly increasing the risk of overexposure at the top. It can effectively eliminate bottom residue and unopened defects after development, suppress the formation of inverted trapezoidal structures, improve sidewall steepness, and avoid top pattern deformation or linewidth loss due to excessive overall dose. Moreover, it does not require changes to the existing development process or the addition of additional film layers.
[0036] Furthermore, the stepwise increase in exposure dose from the top to the bottom of the photoresist includes: firstly, performing top patterning exposure of the photoresist with the first dose, wherein the first dose is 70%-90% of the dose required for the complete formation of the top pattern of the photoresist; The lower middle portion of the photoresist is then subjected to enhanced exposure using the second dosage, which is 150%-300% of the first dosage. This achieves the following technical effects: Precisely control the top graphic outline to avoid overexposure damage: The first dose is slightly lower than 70%-90% of the amount required for full molding, so that the top photochemical reaction reaches the "pre-defined" state rather than over-reaction, effectively avoiding overexposure defects such as top linewidth shrinkage, edge rounding, or adhesive layer deformation.
[0037] Compensating for insufficient energy at the bottom by using a second exposure enhancement: The second dose is 150%-300% higher than the first dose, significantly enhancing the energy input in the middle and lower parts, compensating for the absorption and attenuation of light in the thick adhesive layer, helping the bottom of the adhesive layer to obtain sufficient photochemical reaction energy, and helping to eliminate the problems of bottom residue and unopened areas after development.
[0038] Forming a steep or trapezoidal sidewall structure: By distributing the dosage from low to high, the actual deposition energy distribution of the adhesive layer from top to bottom tends to be uniform. During development, the dissolution rate is consistent along the thickness direction, effectively suppressing the inverted trapezoidal structure (bottom linewidth is greater than top) caused by insufficient dosage at the bottom, and obtaining a near-vertical sidewall morphology.
[0039] Avoid the drawbacks of traditional single high-dose exposure: Unlike the approach of directly increasing the overall dose to 150%-300%, this scheme is implemented in stages: the top only receives a lower dose, so there will be no overexposure at the top; while the high dose in the middle and lower parts can be independently controlled, thus resolving the contradiction of "protecting the bottom while damaging the top".
[0040] Improve sidewall smoothness: Two-step dose exposure allows energy to transition smoothly along the depth of the photoresist layer, which helps to avoid instability at the development front caused by dose abrupt changes and reduces sidewall roughness and standing wave effect traces.
[0041] Highly adaptable to various processes and has a wide application window: Both the first dose (70%-90%) and the second dose (150%-300%) are given a wide range, which can be flexibly adjusted according to the actual adhesive thickness, light absorption coefficient and other parameters, to be compatible with different materials and thickness requirements without changing the development conditions or adding additional process layers.
[0042] Furthermore, the dynamic focus scanning exposure method includes the following steps: dynamically adjusting the position of the focal plane of the exposure operation in the photolithography system, so that the focal plane is scanned stepwise or continuously along the thickness direction of the photoresist, and allocating the dwell time of the focal plane at different positions according to the thickness of the photoresist and the pattern requirements to control the local exposure dose. The dynamic adjustment of the focal plane position for exposure operations in the photolithography system includes: The photolithography system's moving stage is moved longitudinally, causing the photoresist to sequentially enter the focal plane at different depths; and / or, Adjust the adjustable lens group of the photolithography system to change the position of the focal plane of the photolithography system.
[0043] In traditional fixed focal plane exposure, only the film layer near the focal plane obtains high-resolution imaging, while the area far from the focal plane becomes out of focus, resulting in diffused light intensity distribution and decreased energy density.
[0044] This method scans along the thickness direction using the focal plane, ensuring that every depth position of the adhesive layer has the opportunity to be near the optimal focal plane, thereby obtaining a uniform high energy density throughout the entire adhesive thickness range and improving the underexposure caused by defocusing at the bottom.
[0045] Different depth locations can be assigned different scanning dwell times (or scanning speeds), thereby independently controlling the equivalent exposure dose for each depth region. For example, extending the dwell time at the bottom of the adhesive layer (the area with the most severe light attenuation and the greatest risk of defocusing) increases the equivalent dose; shortening the dwell time at the top of the adhesive layer avoids overexposure; and maintaining a normal dwell time in the middle. This allows the actual deposited energy to precisely compensate for absorption attenuation along the thickness direction, helping to achieve ideal homogenization or a specific distribution.
[0046] Traditional fixed focal plane exposure, if a lower numerical aperture (increasing depth of focus) is used to accommodate the bottom, sacrifices lateral resolution. This solution, under high numerical aperture (high resolution) conditions, can achieve clear imaging at all depths through focal plane scanning. At the same time, by adjusting the dose through residence time allocation, it achieves both high resolution and uniform exposure of thick film, which is difficult to achieve with traditional methods.
[0047] Traditional fixed-focal-plane exposure and defocusing can cause blurring of the edges of the lithographic pattern, resulting in non-perpendicular (tilted) sidewalls and rough edges (increased line edge roughness (LER)) after development. The focal-plane scanning in this application ensures clear exposure of patterns at all depths, significantly improving sidewall perpendicularity and reducing roughness after development.
[0048] Traditional fixed focal plane exposure easily forms standing waves (interference between incident light and reflected light from the substrate) within the resist layer, resulting in periodic energy fluctuations and "ripples" or serrated structures on the sidewalls after development. The focal plane scanning in this application is equivalent to time averaging of the interference pattern in the thickness direction, smoothing out the periodic fluctuations in energy distribution and significantly suppressing the standing wave effect.
[0049] This application achieves this by adjusting the focal plane trajectory and dwell time, without involving special developing solutions, multilayer adhesives, or additional process steps, and can be implemented through software control in existing stepper or scanning lithography machines.
[0050] For high aspect ratio structures such as deep holes and trenches, traditional exposure methods struggle to guarantee bottom sharpness and dose. The dynamic focus scanning method in this application allows for flexible allocation of dwell time strategies for different graphic regions (such as densely packed hole areas and isolated line areas), adapting to diverse design needs.
[0051] Furthermore, the spectral optimization exposure method includes the following steps: exposing the photoresist from top to bottom using multiple specified wavelengths of light with gradually increasing penetrating power; The process of forming multiple specified wavelengths of light is as follows: multiple original wavelengths of light are provided by a broadband light source, and the desired specified wavelength of light is selected or combined from the original wavelengths of light by a filtering system.
[0052] By taking advantage of the differences in the absorption characteristics of photoresist to different wavelengths of light sources (such as i-line, g-line, and h-line, i.e., blue light, violet light, and near-ultraviolet light), a wavelength with stronger penetrating power or a combination of multiple wavelengths can be selected for exposure in order to optimize the longitudinal distribution of light energy within the photoresist layer.
[0053] Short-wavelength light (such as ultraviolet light) has high photon energy and high lithographic resolution, but shallow penetration depth and is easily absorbed by the top of the adhesive layer; long-wavelength light (such as near-ultraviolet light) has strong penetrating power and can reach deep into the adhesive layer, but its photon energy is lower and its single reaction efficiency is lower.
[0054] This solution employs a layered wavelength exposure strategy: "high-precision shaping with short wavelengths at the top and deep energy replenishment with long wavelengths at the bottom." Utilizing the inherent differences in penetration ability among different wavelengths, it naturally compensates for light absorption attenuation at a physical level, eliminating the need for large doses or complex motion control. It achieves natural energy compensation by leveraging the physical properties of wavelength and penetration depth.
[0055] Furthermore, by controlling the exposure sequence and relative dose ratio of different wavelengths, the photochemical reaction efficiency in each depth region can be independently optimized. First, a high-resolution pattern is defined at the top using a short wavelength (e.g., 365nm or 248nm). Then, a medium wavelength (e.g., 405nm) is used to compensate for the energy in the middle. Finally, a long wavelength (e.g., 550nm or longer) is used to enhance the exposure at the bottom, which helps to ensure complete reaction at the bottom. This makes the actual chemical reaction degree of the adhesive layer more consistent from top to bottom, resulting in no bottom residue or unopened areas after development, and precisely controlling the degree of photochemical reaction at different depths of the adhesive layer.
[0056] Traditional single-wavelength (especially short-wavelength) exposure, while offering high resolution, suffers from poor penetration, resulting in extremely poor performance on the bottom of thick resist. While using a long-wavelength single light source provides deeper penetration, it reduces lateral resolution and blurs the edges of the top pattern. This solution achieves a balance between high resolution (top) and deep penetration (bottom) through multi-wavelength combination, overcoming the physical limitations of single-wavelength lithography in thick resist lithography and mitigating the trade-offs caused by fixed single-wavelength exposure.
[0057] Different photoresists have different light absorption spectra (such as i-line photoresist, g-line photoresist, and broadband photoresist). The filtering system can dynamically screen or combine wavelengths in real time, and customize the optimal wavelength combination for specific photoresist types and thicknesses (e.g., 2-3 main wavelengths, or gradually changing continuous spectrum), which has high process adaptability.
[0058] Secondly, in traditional single-wavelength exposure, the interference between substrate reflection and incident light easily forms standing waves, leading to periodic energy fluctuations within the adhesive layer. This application utilizes multi-wavelength exposure, where the interference patterns formed by different wavelengths have different phases. After superposition, these patterns cancel each other out or smooth out the interference, effectively suppressing the standing wave effect. After development, the sidewalls are smoother and free of periodic tooth-like stripes, which helps to suppress the standing wave effect and sidewall ripples.
[0059] Broadband light sources have been widely used in lithography equipment. Filtering systems (such as tunable filters, acousto-optic tunable filters (AOTF), liquid crystal tunable filters (LCTF), etc.) can achieve rapid wavelength switching or combination. This can be achieved through software control without replacing the core lithography hardware. By utilizing existing broadband light sources and filtering systems, the method can be cost-effective.
[0060] Furthermore, the auxiliary layer exposure enhancement method includes the following steps: coating an auxiliary layer on the substrate, the auxiliary layer being located below the photoresist, the optical parameters (such as refractive index n) of the auxiliary layer being adapted to the optical parameters of the photoresist, n_auxiliary_layer = (n_photoresist * n_substrate)^0.5, where n is the refractive index.
[0061] An auxiliary layer with specific optical properties (such as low absorption and high reflection) (e.g., a customized anti-reflective coating ARC) is coated on the bottom of the photoresist or the surface of the substrate to reduce light absorption by the substrate and enhance the exposure intensity of the bottom region by utilizing interference effects.
[0062] The optical parameters (refractive index, extinction coefficient, thickness, etc.) of the auxiliary layer are designed to be compatible with the photoresist, and can serve one or more of the following functions: Reduce interface reflection: Match the refractive index to reduce reflection loss at the photoresist-substrate interface, allowing more light energy to remain at the bottom of the photoresist layer; Standing wave manipulation: By changing the thickness and refractive index of the auxiliary layer, the antinodes (energy maxima) of the interference pattern are transferred to the bottom region of the adhesive layer; Refresh exposure is generated: the auxiliary layer itself can absorb light and generate secondary radiation (such as fluorescence, scattered light) or reflection, so as to "refresh" the adhesive layer from the bottom up.
[0063] Without increasing the top dose, the actual received energy at the bottom of the adhesive layer is significantly improved.
[0064] Furthermore, in traditional thick resist lithography, insufficient energy is caused by reflection loss and interference dark areas at the bottom, resulting in slow dissolution or excessive lateral dissolution at the bottom during development, forming an inverted trapezoid with a bottom linewidth greater than the top. The auxiliary layer adapted in this application can distribute energy more evenly to the bottom of the resist layer, making the dissolution rate consistent in the thickness direction during development, and obtaining steep or slightly positive trapezoidal sidewalls.
[0065] In traditional exposure, standing waves are generated by the interference of incident light and reflected light from the substrate, causing periodic fluctuations in energy within the resist layer and resulting in ripples on the sidewalls after development. In this application, the auxiliary layer can function as an anti-reflective layer (ARC) or a bottom anti-reflective coating (BARC), significantly reducing reflectivity through destructive interference or absorption of reflected light, thereby suppressing or eliminating standing waves and resulting in smoother sidewalls.
[0066] For deep holes, through holes, or trenches with high aspect ratios, light has difficulty reaching the bottom corner areas, easily resulting in a thin layer residue or a completely unopened bottom. In this application, the auxiliary layer "diffuses" or "supplements" light energy to these areas that are difficult to be directly illuminated by reflection, scattering, or re-radiation, which helps to ensure a full photochemical reaction at the bottom, resulting in a completely open bottom without any residue after development.
[0067] Traditional methods increase the overall exposure dose to enhance the bottom energy, resulting in the top receiving far more energy than required, causing deformation. In this application, the auxiliary layer method only enhances the bottom energy, while the top dose remains at a normal level, thus resulting in a clear top pattern outline and precise line width.
[0068] The auxiliary layer can be used in conjunction with gradient dosing, dynamic focal scanning, and spectral optimization methods to further optimize energy distribution. For example, the auxiliary layer provides basic reflection / scattering enhancement, which, combined with gradient dosing, finely compensates for remaining inhomogeneities.
[0069] The auxiliary layer is usually a spin-coated organic or inorganic material (such as anti-reflective coating material, polymer, metal oxide film), which is formed by spin coating, deposition and other methods before photoresist coating. It does not increase the complexity of the development or exposure steps, has a high degree of process integration, and can be coated in one step.
[0070] The auxiliary layer can be removed along with the photoresist during the development process (or partially retained as the underlying structure), without adding any extra burden to subsequent processes.
[0071] Further, the development-co-exposure method includes: during the exposure stage, controlling the edge exposure amount at the bottom of the patterned sidewalls of the photoresist through spatially selective dose control to form a modified resist layer region; the control of the edge exposure amount at the bottom of the patterned sidewalls of the photoresist through spatially selective dose control includes: adding sub-resolution auxiliary patterns around the main pattern on the mask, and using diffraction or scattering effects to add additional exposure at the bottom of the sidewalls; and / or, After the main body of the photoresist is exposed, a global exposure operation or a thermal baking operation is introduced to promote the reaction of photosensitive components in the bottom residue of the photoresist. Wherein, the wavelength of the global exposure is not less than the wavelength of the subject exposure, the dose of the global exposure is 10%-50% of the dose of the subject exposure, and the time of the global exposure is 1-10s; The baking temperature is 80-120℃, and the time is 60-300s.
[0072] By precisely controlling the edge exposure, a modified region with a certain width and different properties from the bulk adhesive layer can be formed at the bottom of the pattern sidewall.
[0073] For positive photoresist: the modified region can be designed to be more soluble in the developer, and the bottom of the sidewall will dissolve preferentially during development, forming an undercut or smooth transition, effectively eliminating the "root" phenomenon remaining at the bottom.
[0074] For negative photoresists: the modified region can be designed with a higher degree of cross-linking to enhance the development resistance of the bottom sidewall and prevent sidewall collapse or bottom line retraction due to insufficient bottom dose.
[0075] The common defect in thick photoresist patterns, known as "footing" (i.e., residual photoresist feet extending outwards from the bottom of the sidewalls), is caused by insufficient exposure at the bottom corners. This application addresses this by adding appropriate exposure to the edge areas to match the degree of photochemical reaction at the bottom corners with the upper sidewalls and the bottom planar area, resulting in a smooth, steep bottom profile without footing after development.
[0076] In addition, after the main body is exposed (before development), there may be areas at the bottom of the adhesive layer where only a portion of the photochemical reaction occurs due to a slightly insufficient dose (i.e., "latent insufficiency areas"). These areas may not completely dissolve during conventional development, forming a residual thin layer.
[0077] At this point, global exposure (uniform exposure of the entire adhesive surface without a mask) is introduced: light is used to continue activating the photosensitive components (photoacid generators / photoinitiators) remaining at the bottom, enabling them to complete the required chemical reaction without relying on the patterning capabilities of a high-transmittance light source.
[0078] Alternatively, thermal baking (such as an enhanced version of post-exposure baking for PEB) can be introduced: thermal energy can be used to allow the photosensitive components to continue to diffuse or catalyze the reaction, so that the bottom half-reaction region can reach a fully reactive state.
[0079] Furthermore, traditional methods often result in overexposure of the top by significantly increasing the exposure dose of the main body to improve the bottom dose. This solution adopts a two-stage strategy of "moderate exposure of the main body + global exposure / heat baking in the later stages": the exposure of the main body only needs to ensure accurate shaping of the top and complete reaction of the upper and middle parts; the later stages are used to treat the bottom residue without damaging the already shaped top contour.
[0080] Global exposure or thermal baking can be applied indiscriminately to the entire bottom of the adhesive layer, especially for large areas with dense patterns, effectively eliminating the "incomplete development" phenomenon that is difficult to eradicate with traditional methods. After development, a completely open pattern can be obtained (the bottom of the through-hole is fully exposed and the bottom of the trench is clean), without thin layer residue or flocculent matter.
[0081] When there are slight fluctuations in the photoresist coating thickness (such as thicker at the edges and thinner in the center), setting the main exposure to the average thickness often results in insufficient dose at the bottom of the thick area. Global exposure or thermal baking in subsequent processes can compensate for the deficiency at the bottom of the thick area, while keeping the impact on the thin area controllable (because its bottom may have already fully reacted), thereby improving the overall process yield.
[0082] Global exposure can be performed on the same lithography machine after mask removal, or it can be completed using a separate UV exposure system (such as a photomask or UV oven), resulting in low equipment modification costs. Thermal baking utilizes existing baking equipment (hot plate or oven), requiring only an additional temperature / time-controlled post-baking step. It does not change the core exposure and development parameters, simplifying process integration. Furthermore, it synergizes well with gradient dosing and auxiliary layers. For example, auxiliary layers enhance the initial energy at the bottom, gradient dosing provides depth compensation, and development-assisted exposure (post-process global exposure) serves as a final safeguard, forming a three-layer progressive protection that significantly improves the reliability of leaving no residue at the bottom of thick resist lithography.
[0083] To address the aforementioned technical problems, this application also provides a photolithography system, comprising a control device and a dose and timing control unit electrically connected to the control device; the dose and timing control unit includes a dynamic focusing device and a dose modulation device, both of which are electrically connected to and controlled by the control device; wherein... A control device for generating control commands based on the photoresist thickness and the target pattern; A dynamic focusing device includes a movable workpiece stage and an adjustable lens group. The dynamic focusing device uses the movable workpiece stage and the adjustable lens group to position and scan the focal plane in the thickness direction of the photoresist. A dose modulation device is used in conjunction with the dynamic focusing device to control the exposure energy of the photoresist.
[0084] Furthermore, the dose modulation device adjusts the light intensity by controlling the shutter speed of the exposure light source; and / or, The dose modulation device performs time integration using a spatial light modulator pattern to deliver a local dose to the photoresist.
[0085] When the focal plane of the dynamic focusing device scans to each predetermined position of the photoresist, the exposure time of the photoresist at that position is precisely controlled according to the allocated dwell time, thereby achieving differentiated local dose delivery at different thicknesses of the photoresist.
[0086] Under the command of the control device, the dynamic focusing device and the dose modulation device work together to achieve local optimal focusing and apply customized dose at different thicknesses of photoresist, thereby forming complex three-dimensional or high aspect ratio structures in a single exposure.
[0087] To address the aforementioned technical problems, this application also provides a computer-readable storage medium storing computer-readable instructions, which, when executed by a processor, implement the steps of the aforementioned photolithography method.
[0088] The readable storage medium includes flash memory, hard disk, multimedia card, card-type memory (e.g., SD or DX memory), random access memory (RAM), static random access memory (SRAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), programmable read-only memory (PROM), magnetic memory, magnetic disk, optical disk, etc. In some embodiments, the memory may be an internal storage unit of the computer device, such as the hard disk or RAM of the computer device. In other embodiments, the memory may also be an external storage device of the computer device, such as a plug-in hard disk, smart media card (SMC), secure digital card (SD), flash card, etc., equipped on the computer device. Of course, the memory may include both internal storage units and external storage devices of the computer device. In this embodiment, the memory is typically used to store the operating system and various application software installed on the computer device, such as computer-readable instructions obtained by photolithography. In addition, the memory may also be used to temporarily store various types of data that have been output or will be output.
[0089] The present application will be specifically described below through specific embodiments. The following embodiments are only some embodiments of the present application and are not intended to limit the present application.
[0090] Photolithography System Example 1 like Figure 1As shown, the photolithography system of this embodiment includes a control device 1, a dose and timing control unit 2, and a developing device 3; the dose and timing control unit 2 includes a dynamic focusing device 21 and a dose modulation device 22, and the dynamic focusing device 21, the dose modulation device 22, and the developing device 3 are all electrically connected to the control device 1 and controlled by the control device 1; wherein, Control device 1 is used to generate control commands based on the thickness of the photoresist and the target pattern; The dynamic focusing device 21 includes a high-precision Z-axis moving workpiece stage and an adjustable lens group, used for positioning and scanning the focal plane in the photoresist thickness direction. The dose modulation device 22 is synchronized with the focusing action of the dynamic focusing device 21 and is used to cooperate with the dynamic focusing device 21 to control the exposure energy of different parts of the photoresist.
[0091] The developing device 3 is used to develop the exposed photoresist to complete the photolithography process.
[0092] Photolithography Method Example 1 like Figure 2 As shown, in order to improve the exposure effect, the exposure method of this application embodiment adopts gradient dose exposure method and dynamic focus scanning exposure method, which is implemented by photolithography system embodiment 1.
[0093] The photolithography method of this application includes the following steps: S1. Initialize the control lithography system.
[0094] S2. Exposure Operation: Select the exposure method and exposure mode; The exposure mode includes single-exposure gradient dose loading or step-exposure setting parameters: The single-exposure gradient dose loading refers to the process where, during a single continuous exposure, the exposure dose is controlled by the photolithography system to change in a gradient with time or position. This method does not require interrupting the exposure or changing the mask; instead, the dose switching is automatically completed by the dose and timing control unit.
[0095] In subsequent exposure operations: the low dose E1 in step (1) and the high dose E2 in step (3) are actually different stages of the same exposure, and the dose is automatically switched by the control unit according to the set timing.
[0096] The step-by-step exposure setting parameters refer to dividing the exposure into two independent sub-steps, each with different dose parameters set (for example, performing an exposure E1 first, followed by a second exposure E2 after a certain interval). This may require realigning, changing the mask, or manually adjusting the parameters.
[0097] In this embodiment, the exposure method uses gradient dose exposure and dynamic focus scanning exposure, controlled by a dose and timing control unit. The dose and timing control unit includes a dose modulation device and a dynamic focusing device. The gradient dose exposure and dynamic focus scanning exposure are performed by the dose modulation device and the dynamic focusing device, respectively. The exposure method regulates the energy distribution inside the photoresist to ensure sufficient and uniform exposure at the bottom of the photoresist. The exposure mode uses a single exposure with gradient dose loading.
[0098] The specific steps of the exposure operation are as follows: (1) Provide a silicon substrate, spin-coate AZ4620 photoresist, control the film thickness to be 10 μm, and pre-baking conditions to be 110℃ and 80s. The exposure dose required for complete curing of the top of the photoresist is 200 mJ / cm². In the dose and timing control unit, the local dose of the photoresist is adjusted to the first dose E1 = 180 mJ / cm² (90% of the dose required for complete curing of the top of the photoresist, 200 mJ / cm²) by time integration of the pattern of the spatial light modulator of the dose modulation device. (2) Perform top pattern shaping exposure: The top of the photoresist is exposed for the first time using a mask with the first dose E1 = 180 mJ / cm² to complete the shaping of the top pattern of the photoresist; (3) The dose modulation device is adjusted to switch to a higher second dose E2 = 360 mJ / cm² (200% of E1); (4) The dynamic focusing device positions and scans the focal plane by moving the workpiece stage and the adjustable lens group, and moves it to the lower middle part of the photoresist; (5) Perform "enhanced exposure" on the lower middle part of the photoresist; The total dose of the first and second doses is 540 mJ / cm², which is higher than the critical dose required for complete reaction at the bottom of the photoresist.
[0099] S3. Use developer AZ400K (dilution ratio 1:2), shake and develop for 120s at 23℃ to complete the photolithography.
[0100] The photoresist after photolithography using the method described in this application was observed under a microscope and by SEM, and the results are as follows: Figure 3 As shown, the sidewalls of the graphic are steep, the bottom opening is complete, and there are no residues.
[0101] Comparative Example 1 of Photolithography Method In Comparative Example 1, the traditional exposure method is used for photolithography. The specific steps of this photolithography method are as follows: S1. Provide a silicon substrate, spin-coate AZ4620 photoresist, control the film thickness to 10μm, and pre-baking conditions are 110℃ for 80s.
[0102] S2. Perform proximity exposure with an exposure gap of 5µm, an exposure power of 30mw / cm², and an exposure energy of 650mj / cm². 2 .
[0103] S3. After exposure, let stand for 1 hour.
[0104] S4. Use developer AZ400K (dilution ratio 1:2), shake and develop for 120s at 23℃ to complete the photolithography.
[0105] The photoresist after photolithography using the method in Comparative Example 1 was observed under a microscope and by SEM. The results are as follows: Figure 4 As shown, there is residual developer at the bottom.
[0106] In summary, this application is able to: 1) Significantly improves the uniformity of exposure at the bottom of thick photoresist layers and eliminates developer residue; 2) Improve the verticality of the sidewalls, reduce the inverted trapezoidal phenomenon, and improve the accuracy of graphic transfer; 3) Expand the process window to accommodate a wider range of adhesive thicknesses (e.g., 10μm to 200μm) and different adhesive types (e.g., AZ series). 4) It is mainly achieved through exposure method strategies and parameter adjustments, and is compatible with existing lithography equipment, requiring no expensive hardware modifications; 5) Exposure parameters can be flexibly adjusted through software control, quickly adapting to different process requirements and pattern structures.
[0107] Obviously, the embodiments described above are only some embodiments of this application, not all embodiments. The accompanying drawings show preferred embodiments of this application, but do not limit the patent scope of this application. This application can be implemented in many different forms; rather, the purpose of providing these embodiments is to provide a more thorough and comprehensive understanding of the disclosure of this application. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing specific embodiments, or make equivalent substitutions for some of the technical features. Any equivalent structures made using the content of this application's specification and drawings, directly or indirectly applied to other related technical fields, are similarly within the scope of patent protection of this application.
Claims
1. A photolithography method, characterized in that, include: Control the initialization of the lithography system; Select an exposure method and use the exposure method to adjust the energy distribution inside the photoresist so that the bottom of the photoresist reaches the specified exposure state; The exposure method includes one or more of the following: gradient dose exposure method, dynamic focus scanning exposure method, spectral optimization exposure method, auxiliary layer exposure enhancement method, and development synergistic exposure method; The photolithography process is completed through development.
2. The photolithography method according to claim 1, characterized in that, The gradient dose exposure method includes: dynamically adjusting the exposure dose during a single or step-by-step exposure process, with the exposure dose increasing in a gradient from the top to the bottom of the photoresist.
3. The photolithography method according to claim 2, characterized in that, The stepwise increase in exposure dose from the top to the bottom of the photoresist includes: first, performing top patterning exposure of the photoresist with the first dose, where the first dose is 70%-90% of the dose required for the complete formation of the top pattern of the photoresist; The lower middle portion of the photoresist is then subjected to enhanced exposure using the second dose, which is 150%-300% of the first dose.
4. The photolithography method according to claim 1, characterized in that, The dynamic focus scanning exposure method includes: dynamically adjusting the position of the focal plane of the exposure operation in the photolithography system, so that the focal plane is scanned stepwise or continuously along the thickness direction of the photoresist, and allocating the dwell time of the focal plane at different positions according to the thickness of the photoresist and the pattern requirements to control the local exposure dose. The dynamic adjustment of the focal plane position for exposure operations in the photolithography system includes: The photolithography system's moving stage is moved longitudinally, causing the photoresist to sequentially enter the focal plane at different depths; and / or, Adjust the adjustable lens group of the photolithography system to change the position of the focal plane of the photolithography system.
5. The photolithography method according to claim 1, characterized in that, The spectral optimization exposure method includes the following steps: exposing the photoresist from top to bottom using multiple specified wavelengths of light with gradually increasing penetrating power; The process of forming multiple specified wavelengths of light is as follows: multiple original wavelengths of light are provided by a broadband light source, and the desired specified wavelength of light is selected or combined from the original wavelengths of light by a filtering system.
6. The photolithography method according to claim 1, characterized in that, The auxiliary layer exposure enhancement method includes the following steps: coating an auxiliary layer on a substrate, the auxiliary layer being located below the photoresist, n 辅助层 =(n 光刻胶 *n 基底 )^0.5, where n is the refractive index.
7. The photolithography method according to claim 1, characterized in that, The development-co-exposure method includes: during the exposure stage, controlling the edge exposure amount at the bottom of the patterned sidewalls of the photoresist through spatially selective dose control to form a modified photoresist layer region; the control of the edge exposure amount at the bottom of the patterned sidewalls of the photoresist through spatially selective dose control includes: adding sub-resolution auxiliary patterns around the main pattern on the mask, and using diffraction or scattering effects to add additional exposure at the bottom of the sidewalls; and / or, After the main body of the photoresist is exposed, a global exposure operation or a thermal baking operation is introduced to promote the reaction of photosensitive components in the bottom residue of the photoresist. Wherein, the wavelength of the global exposure is not less than the wavelength of the subject exposure, the dose of the global exposure is 10%-50% of the dose of the subject exposure, and the time of the global exposure is 1-10s; The baking temperature is 80-120℃, and the time is 60-300s.
8. A photolithography system, characterized in that, The system includes a control device and a dose and timing control unit electrically connected to the control device; the dose and timing control unit includes a dynamic focusing device and a dose modulation device, both of which are electrically connected to and controlled by the control device; wherein... A control device for generating control commands based on the photoresist thickness and the target pattern; A dynamic focusing device includes a movable workpiece stage and an adjustable lens group. The dynamic focusing device uses the movable workpiece stage and the adjustable lens group to position and scan the focal plane in the thickness direction of the photoresist. A dose modulation device is used in conjunction with the dynamic focusing device to control the exposure energy of the photoresist.
9. The photolithography system according to claim 8, characterized in that, The dose modulation device is used to adjust the light intensity; and / or, The dose modulation device performs time integration using a spatial light modulator pattern to deliver a local dose to the photoresist.
10. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores computer-readable instructions, which, when executed by a processor, implement the steps of the photolithography method as described in any one of claims 1 to 7.