Method for improving thick metal wet etch process

Abstract

The application provides a thick metal wet etching process improvement method, and relates to the technical field of wet etching.The method comprises the following steps: performing one-time wet etching on a metal film layer to be etched covered by a photoresist film layer, and continuously monitoring the corrosion width of the sidewall of the etched part; when the corrosion width is greater than a preset value, the present wet etching is terminated; heating the metal film layer to be etched after the present wet etching is completed, so that the photoresist film layer naturally collapses and covers and protects the sidewall of the etched part; after the photoresist film layer is reshaped, the above steps are cyclically executed until the etching is completed, and the metal film layer after the etching is completed is obtained.The method of the application aims to solve the problem that the thick metal wet etching becomes difficult to control due to the increase of the metal film thickness, can ensure that the sidewall corrosion is controllable in the etching process of the thick metal film layer, avoids over-corrosion of the sidewall, thereby ensuring the integrity of the required pattern and avoiding distortion of the appearance.

Description

Technical Field

[0001] This invention relates to the field of wet etching technology, and more specifically, to an improved method for wet etching processes of thick metals. Background Technology

[0002] Metal wet etching technology refers to a process where a wafer already coated with a corresponding metal film is covered with a photoresist protective film using photolithography, and then immersed in a wet chemical solution. The unwanted metal is removed through a chemical reaction, resulting in the desired metal morphology. In traditional wet etching processes, due to the isotropic nature of wet etching, the difficulty of controlling thick metal wet etching increases progressively with the thickness of the metal film, sometimes even becoming uncontrollable, ultimately leading to complete morphology distortion.

[0003] There is currently no effective technical solution to the above problems. Summary of the Invention

[0004] The purpose of this invention is to provide an improved method for thick metal wet etching process, which aims to solve the problem that thick metal wet etching becomes difficult to control due to the increase in metal film thickness. It can ensure that sidewall corrosion is controllable during the etching process of thick metal film, avoid over-corrosion of sidewalls, thereby ensuring the integrity of the required pattern and avoiding morphological distortion.

[0005] In a first aspect, the present invention provides a method for improving a wet etching process for thick metals, comprising the following steps:

[0006] S1. A photoresist film is applied to a predetermined position on the surface of the metal film to be etched, wherein the thickness of the photoresist film is at least twice the thickness of the metal film to be etched;

[0007] S2. Perform a wet etching process on the metal film layer to be etched after covering the photoresist film layer, and continuously monitor the corrosion width of the sidewall of the etched part in the metal film layer to be etched;

[0008] S3. When the corrosion width is greater than the preset value, terminate the current wet etching and rinse and spin dry the metal film layer to be etched;

[0009] S4. Heat the metal film layer to be etched after completing this wet etching process to make the photoresist film layer fluid, and stop heating after the photoresist film layer collapses naturally and covers and protects the sidewalls of the etched part in the metal film layer to be etched.

[0010] S5. After the photoresist film layer is reshaped, return to step S2 until all etched parts in the metal film layer to be etched are completely etched to obtain a metal film layer that has been completely etched.

[0011] The improved method for wet etching of thick metals provided by this invention heats the photoresist during the etching process, causing the photoresist to cover and protect the exposed metal sidewalls. This effectively ensures that these protected sidewalls will not be further eroded in subsequent etching cycles, thereby effectively maintaining the integrity and accuracy of the pattern.

[0012] Furthermore, the specific steps in step S2 include:

[0013] The corrosion width of the sidewall of the etched portion in the metal film to be etched is continuously monitored using optical detection methods or electron microscopy.

[0014] Furthermore, the step of continuously monitoring the corrosion width of the sidewall of the etched portion in the metal film layer using optical detection methods includes:

[0015] S21. Emit a probe beam toward the sidewall region of the etched area;

[0016] S22. Receive the first detection beam reflected by the sidewall region and acquire the spectral data of the first detection beam;

[0017] S23. Determine the corrosion width based on the spectral data.

[0018] It enables non-contact, real-time, and high-precision monitoring of the sidewall corrosion width of the etched area during wet etching of thick metals. This avoids interference with the etching process, improves the automation level of monitoring and the timeliness of data acquisition, thereby enabling more precise control of etching depth and sidewall morphology, effectively suppressing lateral corrosion, and improving the stability and yield of the etching process.

[0019] Furthermore, the specific steps in step S23 include:

[0020] The corrosion width is determined by analyzing the changes in light intensity or the shifts in the positions of spectral peaks and valleys within a specific wavelength range in the spectral data.

[0021] Furthermore, in step S4, the specific steps of heating the metal film layer to be etched after this wet etching to make the photoresist film layer fluid include:

[0022] A hot plate is used to bake and heat the metal film layer to be etched after the wet etching process is completed.

[0023] Furthermore, the baking temperature of the hot plate is 100℃-150℃.

[0024] Furthermore, in step S4, after the photoresist film layer naturally collapses and covers and protects the sidewalls of the etched portion in the metal film layer, the step of stopping heating includes:

[0025] S41. During the heating process of the metal film layer to be etched, a probe beam is continuously emitted towards the boundary region between the edge of the photoresist film layer and the sidewall of the metal film layer to be etched;

[0026] S42. Receive the second detection beam reflected from the boundary region and acquire the optical characteristic data of the second detection beam;

[0027] S43. Based on the optical feature data, determine whether the photoresist film layer has covered the sidewall of the etched part in the metal film layer to be etched;

[0028] S44. When it is determined that the photoresist film has covered the sidewall of the etched part in the metal film to be etched, heating is stopped.

[0029] This ensures that the sidewalls of the etched portion of the metal film are adequately protected during subsequent wet etching processes, thereby improving etching accuracy and yield. Its advantages are even more pronounced for wet etching processes of thick metal films.

[0030] Furthermore, the optical characteristic data includes the ratio of reflected light intensity at a specific wavelength, the polarization rotation angle, and the ratio of the intensity of a specific spectral peak to the background intensity.

[0031] Furthermore, the thickness of the metal film to be etched is greater than or equal to 3.5 μm.

[0032] Furthermore, the metal film to be etched is made of copper, aluminum, or an aluminum alloy.

[0033] As can be seen from the above, the improved wet etching process for thick metals provided by this invention decomposes the wet etching process of thick metals into multiple controlled, iterative "etch-reprotection" cycles. By interrupting the etching process each time a specific sidewall etching amount is reached, and utilizing the flow characteristics of photoresist during heating, the exposed metal sidewalls are dynamically re-covered and protected. This prevents further erosion of the formed sidewalls in subsequent etching cycles, ensuring the integrity of the pattern.

[0034] Other features and advantages of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing embodiments of the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures particularly pointed out in the written description and the accompanying drawings. Attached Figure Description

[0035] Figure 1 This is a flowchart of an improved method for wet etching of thick metals provided in an embodiment of the present invention.

[0036] Figure 2 This is a schematic diagram of the etching process in an embodiment of the present invention.

[0037] 100, Metal film to be etched; 200, Photoresist film; 300, Sidewall. Detailed Implementation

[0038] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0039] It should be noted that similar reference numerals and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. Furthermore, in the description of this invention, terms such as "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0040] Reference Appendix Figure 1 and attached Figure 2 This invention provides an improved method for wet etching of thick metals, comprising the following steps:

[0041] S1. A photoresist film is placed at a predetermined position on the surface of the metal film to be etched, and the thickness of the photoresist film is at least twice the thickness of the metal film to be etched.

[0042] S2. Perform a wet etching process on the metal film to be etched after covering the photoresist film layer, and continuously monitor the corrosion width of the sidewall of the etched part in the metal film layer (different from the preset position, the position not covered by the photoresist film layer is corroded due to the exposed metal, and the corroded metal part is also the etched part). The corrosion width refers to the distance that the sidewall of the etched part is corroded in the lateral direction, which is a key indicator for measuring the degree of lateral corrosion.

[0043] S3. When the corrosion width exceeds the preset value, terminate the wet etching process and rinse and spin dry the metal film to be etched.

[0044] S4. Heat the metal film layer to be etched after completing this wet etching process to make the photoresist film layer fluid, and stop heating after the photoresist film layer collapses naturally and covers and protects the sidewalls of the etched part in the metal film layer.

[0045] S5. After the photoresist film layer is reshaped, return to step S2 until all etched parts in the metal film layer are completely etched, and the etched metal film layer is obtained.

[0046] In step S1, a photoresist film layer 200 is applied to a predetermined location on the surface of the metal film layer 100 to be etched. The thickness of the photoresist film layer 200 is set to be at least twice the thickness of the metal film layer 100 to be etched. For example, the photoresist can be uniformly coated onto the surface of the metal film layer 100 to be etched by spin coating, spraying, or lamination, and the photoresist film layer 200 can be formed at the predetermined location through exposure and development processes. The thickness of the photoresist film layer 200 can be precisely controlled by adjusting parameters such as spin coating speed, photoresist viscosity, or number of coating passes.

[0047] In step S2, a wet etching process is performed on the metal film layer 100 covered with the photoresist film layer 200, and the corrosion width of the sidewall 300 of the etched portion in the metal film layer 100 is continuously monitored. Wet etching can be performed by immersing the wafer in an etching solution. The type and concentration of the etching solution are selected based on the material properties of the metal film layer 100. For example, a ferric chloride solution can be used for copper films; a mixed solution of phosphoric acid, nitric acid, and acetic acid can be used for aluminum films. Continuous monitoring of the corrosion width is crucial during the etching process. Various monitoring methods can be employed; for example, a high-resolution camera can be used to acquire images, and then image processing software can be used to analyze the corrosion status of the sidewall 300.

[0048] In step S3, when the etching width exceeds a preset value, the wet etching process is terminated, and the metal film layer 100 to be etched is rinsed and dried. The preset value can be determined based on experience or experimental data, aiming to control lateral corrosion within an acceptable range. After etching is terminated, the wafer needs to be thoroughly rinsed with deionized water immediately to remove residual etching solution and reaction products, preventing further corrosion. Subsequently, the moisture on the wafer surface is removed by methods such as spin drying or nitrogen purging.

[0049] In step S4, the metal film layer 100 to be etched after this wet etching is heated to make the photoresist film layer 200 fluid. Heating is stopped after the photoresist film layer 200 naturally collapses and covers and protects the sidewalls 300 of the etched area in the metal film layer 100. Heating can be achieved in various ways, such as using a hot air gun to locally heat the wafer, or placing the wafer on a heating stage for overall baking. The heating temperature and time need to be adjusted according to the characteristics of the photoresist to ensure that the photoresist softens and flows without excessive degradation. During the heating process, the flow of the photoresist film layer 200 can be continuously observed. Heating can be stopped when the edge of the photoresist film layer 200 begins to collapse and cover the sidewalls 300 of the etched area.

[0050] In step S5, after the photoresist film layer 200 is reshaped, the process returns to step S2 until all etched areas in the metal film layer 100 are completely etched, resulting in a fully etched metal film layer. After cooling, the photoresist film layer 200 will re-solidify and form a new protective layer, effectively covering and protecting the sidewalls 300 of the etched areas, thereby limiting lateral corrosion in subsequent etching processes. Subsequently, wet etching can be performed again, and the above steps can be repeated until the entire metal film layer is completely etched, forming the desired pattern.

[0051] The improved thick metal wet etching process proposed in this application effectively solves the problem of uncontrollable lateral corrosion in thick metal wet etching by introducing a strategy of step-by-step etching and photoresist sidewall protection. Due to its isotropic nature, traditional wet etching causes lateral corrosion to significantly increase with etching depth when etching thick metal films, leading to distorted etching morphology. This application addresses this by providing step-by-step photoresist protection to the sidewalls of the etched areas during the etching process, decomposing a single deep etching into multiple shallow etching steps, and utilizing the fluidity of the photoresist to "backfill" and protect the sidewalls after each etching step.

[0052] Specifically, after each wet etching step reaches the preset etching width, etching is stopped, and the photoresist film is heated to soften and collapse naturally, covering and protecting the etched sidewalls. This "adaptive" sidewall protection mechanism ensures that subsequent etching processes are primarily concentrated in the vertical direction, significantly suppressing further lateral corrosion. Compared to traditional single-step etching, the method in this application can more precisely control the etching morphology, significantly reducing lateral corrosion and resulting in steeper, more precise metal lines and structures. This combination of step-by-step etching and dynamic sidewall protection enables wet etching of thick metal films to meet the requirements of precise morphology control in high-density, high-performance integrated circuit manufacturing, improving process yield and device reliability.

[0053] In some embodiments, the specific steps in step S2 include:

[0054] The corrosion width of the sidewall of the etched part in the metal film is continuously monitored using optical detection methods or electron microscopy.

[0055] Optical detection methods typically utilize the principle of light-matter interaction to obtain information about the object of measurement by analyzing the characteristics of reflected, transmitted, or scattered light. For example, microscopes and spectrometers can be used to observe the morphology, size, or optical properties of the sidewalls of an etched area in real-time or near real-time. The aim is to provide a non-contact, relatively rapid monitoring method. Electron microscopy, on the other hand, typically involves using a high-energy electron beam to scan the sample surface and obtain information about the sample's surface morphology and composition by detecting secondary electrons and backscattered electrons. For example, scanning electron microscopy (SEM) can be used to perform high-resolution imaging and measurement of the microstructure and corrosion width of the sidewalls of an etched area. The aim is to provide a high-precision, high-resolution monitoring method, particularly suitable for accurately measuring the corrosion width of small-sized or complex-morphological areas.

[0056] In some embodiments, the step of continuously monitoring the corrosion width of the sidewall of the etched portion in the metal film using an optical detection method includes:

[0057] S21. Emit a probe beam toward the sidewall region of the etched area;

[0058] S22. Receive the first detection beam reflected from the sidewall region and acquire the spectral data of the first detection beam;

[0059] S23. Determine the corrosion width based on the spectral data.

[0060] Specifically, the specific steps in step S23 include:

[0061] The corrosion width is determined by analyzing the changes in light intensity or the shifts in the positions of spectral peaks and valleys within a specific wavelength range in the spectral data.

[0062] Specifically, in step S21, the probe beam can be light emitted from a laser, LED light source, or broadband light source. Its wavelength range can be selected based on the optical properties of the metal film and photoresist film to be etched, ensuring effective penetration of the etching solution and interaction with the sidewall surface. The probe beam is directed towards the sidewall region of the etched area, for example, by focusing and guiding it using a fiber optic probe or optical lens system, to ensure the beam accurately illuminates the sidewall surface to be monitored.

[0063] In step S22, the first probe beam reflected from the sidewall region is captured by a receiver (e.g., a spectrometer, photodiode array, or CCD detector). The receiver converts the reflected light signal into an electrical signal and further processes it to obtain spectral data of the first probe beam. The spectral data typically includes information on the distribution of reflected light intensity with wavelength, which contains key optical characteristics such as sidewall surface morphology, roughness, and material composition.

[0064] In step S23, the etching width can be determined by in-depth analysis of the acquired spectral data. Specifically, as wet etching progresses, the sidewalls of the etched portion of the metal film are gradually etched, resulting in changes to their surface morphology, roughness, and any existing etching products. These changes can alter the intensity of reflected light within a specific wavelength range or cause shifts in the positions of characteristic peaks (such as absorption or reflection peaks) or valleys in the spectrum. For example, as the sidewall etching width increases, the tilt angle or roughness of the sidewalls may change, affecting the scattering characteristics of reflected light and causing a decrease or increase in the intensity of reflected light at a specific wavelength. Furthermore, if a new surface layer is formed or the optical constants of the material are altered during etching, it can also cause shifts in spectral peaks and valleys. By using pre-established calibration curves or physical models, these changes in spectral characteristics are correlated with the actual etching width, thereby achieving precise quantification of the etching width.

[0065] This application's solution utilizes optical detection methods to achieve non-contact, real-time monitoring of the sidewall corrosion width during the wet etching process of thick metals. Based on the principle of light-matter interaction, this method indirectly infers the degree of sidewall corrosion by analyzing the spectral characteristics of the light beam reflected from the sidewall. When the metal film is etched, the morphology, roughness, and material composition of its sidewall change. These changes directly affect the sidewall's reflection characteristics of the incident probe light beam, specifically manifested as variations in the intensity of reflected light within a specific wavelength range, or shifts in the positions of spectral peaks and valleys. Real-time monitoring and analysis of these optical characteristic data allows for precise quantification of the sidewall corrosion width, thus providing a reliable basis for subsequent etching termination determination.

[0066] The above technical solution enables non-contact, real-time, and high-precision monitoring of the sidewall corrosion width of the etched area during wet etching of thick metals. Compared to traditional visual inspection or offline measurement methods, this optical detection method avoids interference with the etching process, improves the automation level of monitoring and the timeliness of data acquisition, thereby enabling more precise control of etching depth and sidewall morphology, effectively suppressing lateral corrosion, and improving the stability and yield of the etching process.

[0067] In some embodiments, step S4, which involves heating the metal film layer to be etched after the wet etching process to make the photoresist film layer fluid, includes the following specific steps:

[0068] A hot plate is used to bake and heat the metal film layer to be etched after the wet etching process is completed.

[0069] A hot plate is a commonly used heating device, characterized by its ability to provide a uniform and controllable heating environment. By placing the metal film to be etched on the hot plate for baking, it is ensured that the photoresist film is heated evenly from the bottom, avoiding localized overheating or underheating. The baking temperature and time can be precisely controlled according to the specific material properties of the photoresist film and the required fluidity to achieve the best softening effect.

[0070] The solution proposed in this application employs a hot plate to bake and heat the metal film layer to be etched after wet etching, providing a controlled and uniform heating method. The surface temperature of the hot plate is typically uniformly distributed, and when the metal film layer to be etched is placed on it, heat can be stably transferred to the photoresist film layer via conduction. This uniform heat transfer ensures that the photoresist film layer as a whole reaches the required softening temperature, enabling it to achieve flowability in a predictable manner, thus allowing for natural collapse in subsequent steps and effectively covering and protecting the sidewalls of the etched area. Compared to other heating methods that may lead to localized overheating or uneven heating, hot plate baking can better control the viscosity changes of the photoresist film layer, laying the foundation for its precise flow and shaping.

[0071] The above technical solution, employing a hot plate for baking, effectively solves the problem of uneven heating of the photoresist film layer that may occur with traditional heating methods. This allows the photoresist film layer to achieve fluidity in a more uniform and controllable manner, ensuring that it can completely and effectively cover and protect the sidewalls of the etched areas in the metal film layer during natural collapse. This significantly improves the reliability and consistency of sidewall protection in thick metal wet etching processes, ultimately contributing to more accurate etching patterns and higher yields.

[0072] In some embodiments, the baking temperature of the hot plate is 100°C-150°C.

[0073] In some embodiments, step S4, after the photoresist film layer collapses naturally and covers and protects the sidewalls of the etched portion in the metal film layer, the step of stopping heating includes:

[0074] S41. During the heating process of the metal film to be etched, a probe beam is continuously emitted towards the boundary area between the edge of the photoresist film and the sidewall of the metal film to be etched.

[0075] S42. Receive the second detection beam reflected from the boundary region and acquire the optical characteristic data of the second detection beam;

[0076] S43. Based on optical characteristic data, determine whether the photoresist film has covered the sidewall of the etched part in the metal film to be etched;

[0077] S44. When it is determined that the photoresist film has covered the sidewall of the etched part in the metal film to be etched, stop heating.

[0078] Specifically, in step S41, the probe beam can be a narrowband light source, such as a laser beam or an LED light source within a specific wavelength range, which is directionally emitted to the boundary region between the edge of the photoresist film layer and the sidewall of the metal film layer to be etched. This region is a key location where the photoresist film layer flows and covers the sidewall. In step S42, the second probe beam refers to the light reflected back from this boundary region, and its optical characteristic data may include, but is not limited to, reflected light intensity, polarization state, and spectral distribution. These optical characteristics change as the photoresist film layer gradually flows and covers the sidewall during the heating process. In step S43, by analyzing these optical characteristic data, for example, a correspondence model between the photoresist film layer coverage state and specific optical characteristic data can be established in advance. When the actually monitored optical characteristic data matches the characteristics of the preset coverage completion state, it can be determined that the photoresist film layer has completed coverage. For example, after the photoresist film layer covers the sidewall, the reflectivity or polarization characteristics of this region will change significantly. In step S44, once it is determined that the photoresist film layer has effectively covered the sidewall, heating can be stopped immediately to avoid unnecessary energy consumption and potential overheating risks.

[0079] This application's solution addresses the challenge of accurately determining the completion timing of photoresist film sidewall coverage in traditional methods by introducing a real-time optical monitoring mechanism. During heating, the photoresist film gradually softens and flows towards the sidewalls of the etched portion of the metal film. When the photoresist film begins to cover the sidewalls, significant changes occur in the surface morphology, material composition, and optical interface properties of the region where its edge meets the sidewall. By continuously emitting a probe beam and receiving the reflected second probe beam, these dynamic changes in optical characteristic data can be captured. For example, when the photoresist film completely covers the sidewalls, the previously exposed metal surface is replaced by the photoresist film, resulting in detectable changes in the intensity, spectrum, or polarization characteristics of the reflected light. Based on this real-time acquired optical characteristic data, the system can accurately determine whether the photoresist film has reached the expected coverage state, thereby achieving precise control of the heating process and ensuring that heating is stopped at the optimal time.

[0080] Through the above technical solution, this application enables real-time and precise monitoring and control of the photoresist film sidewall coverage process. Compared to methods relying on experience or timed heating, this solution significantly improves the reliability and consistency of photoresist film sidewall protection, effectively avoiding sidewall protection defects caused by insufficient heating or performance degradation of the photoresist film caused by overheating. Therefore, it ensures that the sidewalls of the etched areas in the metal film are adequately protected during subsequent wet etching, thereby improving etching accuracy and yield. This advantage is particularly pronounced for wet etching processes of thick metal films.

[0081] In some embodiments, the optical characteristic data includes the ratio of reflected light intensity at a specific wavelength, the polarization rotation angle, and the ratio of the intensity of a specific spectral peak to the background intensity.

[0082] In some embodiments, the thickness of the metal film to be etched is greater than or equal to 3.5 μm.

[0083] In some embodiments, the metal film to be etched is made of copper, aluminum, or an aluminum alloy.

[0084] In this document, relational terms such as first and second are used only to distinguish one entity or operation from another entity or operation, without necessarily requiring or implying any such actual relationship or order between these entities or operations.

[0085] The above description is merely an embodiment of the present invention and is not intended to limit the scope of protection of the present invention. For those skilled in the art, the present invention can have various modifications and variations. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for improving the wet etching process for thick metals, characterized in that, Includes the following steps: S1. A photoresist film is applied to a predetermined position on the surface of the metal film to be etched, wherein the thickness of the photoresist film is at least twice the thickness of the metal film to be etched; S2. Perform a wet etching process on the metal film layer to be etched after covering the photoresist film layer, and continuously monitor the corrosion width of the sidewall of the etched part in the metal film layer to be etched; S3. When the corrosion width is greater than the preset value, terminate the current wet etching and rinse and spin dry the metal film layer to be etched; S4. Heat the metal film layer to be etched after completing this wet etching process to make the photoresist film layer fluid, and stop heating after the photoresist film layer collapses naturally and covers and protects the sidewalls of the etched part in the metal film layer to be etched. S5. After the photoresist film layer is reshaped, return to step S2 until all etched parts in the metal film layer to be etched are completely etched to obtain a metal film layer that has been completely etched. Step S2 includes continuously monitoring the corrosion width of the sidewall of the etched portion in the metal film layer using optical detection methods or electron microscopy. The specific steps include: S21. Emit a probe beam toward the sidewall region of the etched area; S22. Receive the first detection beam reflected from the sidewall region of the etched area, and acquire the spectral data of the first detection beam; S23. Based on the spectral data, determine the corrosion width by analyzing the changes in light intensity or the shifts in the positions of spectral peaks and valleys within a specific wavelength range in the spectral data; The thickness of the metal film to be etched is greater than or equal to 3.5 μm.

2. The method for improving the wet etching process for thick metals according to claim 1, characterized in that, In step S4, the specific steps for heating the metal film layer to be etched after this wet etching process to make the photoresist film layer fluid include: A hot plate is used to bake and heat the metal film layer to be etched after the wet etching process is completed.

3. The method for improving the wet etching process for thick metals according to claim 2, characterized in that, The baking temperature of the hot plate is 100℃-150℃.

4. The method for improving the wet etching process for thick metals according to claim 1, characterized in that, In step S4, after the photoresist film layer collapses naturally and covers and protects the sidewalls of the etched portion in the metal film layer, the step of stopping heating includes: S41. During the heating process of the metal film layer to be etched, a probe beam is continuously emitted towards the boundary region between the edge of the photoresist film layer and the sidewall of the metal film layer to be etched; S42. Receive the second detection beam reflected from the boundary region and acquire the optical characteristic data of the second detection beam; S43. Based on the optical feature data, determine whether the photoresist film layer has covered the sidewall of the etched part in the metal film layer to be etched; S44. When it is determined that the photoresist film has covered the sidewall of the etched part in the metal film to be etched, heating is stopped.

5. The method for improving the wet etching process for thick metals according to claim 4, characterized in that, The optical characteristic data includes the ratio of reflected light intensity at a specific wavelength, the polarization rotation angle, and the ratio of the intensity of a specific spectral peak to the background intensity.

6. The method for improving the wet etching process for thick metals according to claim 1, characterized in that, The metal film to be etched is made of copper, aluminum, or aluminum alloy.

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