A polyimide film release method based on wet release
By coating polymethyl methacrylate (PMMA) onto a silicon wafer as a sacrificial layer and swelling it with an organic solvent, combined with photolithography and segmented temperature control, the high-temperature curing compatibility problem of polyimide films was solved, enabling low-damage, high-integrity mass production suitable for flexible electronic devices.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SUZHOU BONA MICROELECTRONICS TECHNOLOGY CO LTD
- Filing Date
- 2026-02-06
- Publication Date
- 2026-05-29
AI Technical Summary
Existing technologies struggle to achieve high-temperature curing, low-damage, and high-integrity release during the demolding process of polyimide films. Furthermore, they are difficult to mass-produce on a large scale or in multiple batches. Laser demolding equipment is expensive and difficult to maintain, while mechanical peeling can easily cause film tearing.
The silicon wafer is cleaned with concentrated sulfuric acid and hydrogen peroxide to form a hydrophilic surface. Polymethyl methacrylate is then coated as a sacrificial layer. The polyimide film is wet-released by swelling with an organic solvent. Combined with photolithography and segmented temperature control, the integrity of the film is ensured.
It achieves low-damage, high-integrity release of polyimide films, reduces equipment costs, supports simultaneous processing of multiple films, is suitable for large-scale production of flexible electronic devices, and avoids carbonization and dielectric degradation.
Smart Images
Figure CN122103632A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of flexible electronic device manufacturing technology, and in particular to a method for releasing and demolding polyimide films based on wet release. Background Technology
[0002] Currently, the mainstream demolding process for polyimide (PI) films is laser demolding, which uses a specific wavelength laser to act on the PI and the substrate, selectively thermally decomposing the substrate to separate the substrate and the PI film. However, during this process, the local temperature of the PI film can rise instantaneously to 600-1000℃, which can easily cause carbonization, cracking, or degradation of dielectric properties, affecting device reliability. In addition, laser demolding is usually only possible for single-piece demolding, and cannot be performed on large areas or in batches. Furthermore, laser equipment is expensive and complex to maintain, making it difficult to meet the needs of large-scale production.
[0003] Furthermore, demolding by mechanical peeling, thermal stress peeling, or other methods can easily cause localized tearing, warping, or stress cracks in the PI film, and it is difficult to precisely control the film shape, thus limiting its application in flexible electronic devices.
[0004] Some studies have attempted to use water-soluble or low-temperature volatile materials as sacrificial layers to achieve wet release and demolding of PI films. However, such materials are difficult to withstand the high-temperature conditions required for PI curing and are prone to decomposition or failure during processing, resulting in film surface contamination or patterning failure.
[0005] In the field of microstructure fabrication (MEMS), the separation strategy of sacrificial layer-structural layer is relatively mature. By introducing an intermediate layer that can be selectively removed from the substrate, interface stability can be maintained during the processing stage, and structural separation can be achieved during the release stage. However, the inorganic sacrificial layer systems commonly used in MEMS mostly rely on strong HF-type etching solutions, which have poor compatibility with the multi-material systems required for flexible electronics and are difficult to use directly in the demolding process of PI thin films.
[0006] Therefore, the existing technology lacks a sacrificial layer system that is compatible with the high-temperature curing process of polyimide, can be completely removed in subsequent wet processes, has moderate interfacial adhesion, and has good material compatibility. Summary of the Invention
[0007] Objective: In order to overcome the shortcomings of the existing technology, the present invention provides a method for releasing and demolding polyimide films based on wet release, which achieves low-damage and high-integrity release of polyimide films after preparation. Based on this method, polyimide films can be prepared in batches.
[0008] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:
[0009] This invention provides a wet-release method for releasing and demolding polyimide films, comprising: Silicon wafers are cleaned with concentrated sulfuric acid and hydrogen peroxide and treated with oxygen plasma to obtain silicon wafers with hydrophilic surfaces, which are then dried. A sacrificial layer material is coated onto a silicon wafer with a hydrophilic surface and then cured to obtain a silicon wafer with a sacrificial layer. A polyimide solution is spin-coated onto the sacrificial layer, and the polyimide film is patterned by photolithography and then cured to obtain a silicon wafer with a polyimide film and a sacrificial layer attached. The silicon wafer with the attached polyimide film and sacrificial layer is placed in an organic solvent and immersed. The sacrificial layer swells until a continuous separation interface is formed at the edge of the polyimide film. When the entire polyimide film separates from the silicon wafer under slight disturbance of the organic solvent, the film can be removed, and the polyimide film is released and demolded to obtain the complete polyimide film. The sacrificial layer material is a polymer material that swells or dissolves in an organic solvent and is resistant to the curing temperature of polyimide.
[0010] Preferably, the sacrificial layer material is polymethyl methacrylate (PMMA). PMMA has excellent thermal stability, with a thermal decomposition temperature exceeding 300°C; it also exhibits good solubility in organic solvents such as acetone, ethanol, and NMP, making it a preferred material in this invention.
[0011] Furthermore, the polyimide is a photosensitive polyimide.
[0012] The wet-release polyimide film release and demolding method provided by this invention is based on microstructure manufacturing technology. It uses polymethyl methacrylate, which has high temperature stability and can be dissolved in organic solvents, as a sacrificial layer. Through wet selective removal, it achieves low-damage and high-integrity release of the polyimide film, thereby overcoming the limitations of the prior art.
[0013] In some embodiments, the cleaning method for the silicon substrate includes cleaning the silicon substrate with a mixture of concentrated sulfuric acid and hydrogen peroxide; wherein the volume ratio of the concentrated sulfuric acid to hydrogen peroxide is 7:3, 2:1, 3:1, 4:1, or 5:1.
[0014] In some embodiments, the drying method for the silicon wafer having a hydrophilic surface includes drying it in a nitrogen atmosphere.
[0015] In some embodiments, the method for coating the sacrificial layer material includes: using a spin coater to spin coat the sacrificial layer material onto a silicon wafer with a hydrophilic surface at a low speed of 500-1000 rpm for 5-10 seconds, and then spin coating it at a high speed of 2000-4000 rpm for 30-60 seconds.
[0016] In some embodiments, the curing method after coating a sacrificial layer material on a silicon wafer with a hydrophilic surface includes: placing the silicon wafer coated with the sacrificial layer material on a hot plate at 150-200°C and baking it for 2-5 minutes.
[0017] In some embodiments, the thickness of the sacrificial layer is 200-1000 nm.
[0018] In some embodiments, the spin-coating method for polyimide includes: spin-coating at 1000-1200 rpm for 8-15 s, spin-coating at 3500-4000 rpm for 25-35 s, and spin-coating at 1500-2000 rpm for 5-8 s.
[0019] In some embodiments, the thickness of the film formed on the sacrificial layer is 2-50 μm.
[0020] In some embodiments, the curing process of the polyimide film adopts a segmented temperature control: first, the solvent is removed in an environment of 80-120°C for 4-5 minutes, then imidization reaction is carried out in a nitrogen environment at 150-200°C, and finally, complete curing is carried out in an environment of 200-280°C for 2-2.5 hours.
[0021] Using segmented temperature-controlled curing of polyimide films can ensure that the mechanical and dielectric properties of polyimide reach their optimal state, and the temperature during this process will not have an adverse effect on the sacrificial layer, allowing the sacrificial layer to maintain structural integrity.
[0022] Optionally, further processing can be performed on the polyimide film, such as metal vapor deposition.
[0023] In some embodiments, the organic solvent is acetone or N-methylpyrrolidone.
[0024] In some embodiments, the swelling rate of the sacrificial layer can be adjusted by regulating the solvent temperature. After the silicon wafer with the attached polyimide film and sacrificial layer is placed in an organic solvent, the temperature of the organic solvent is adjusted to 50-60°C. For example, acetone is used as the organic solvent; since acetone has a boiling point of 56°C, the temperature of the acetone can be adjusted to 50°C. Other organic solvents with boiling points exceeding 60°C, such as N-methylpyrrolidone, can be used to adjust the temperature of the organic solvent to 60°C.
[0025] When a silicon wafer with a polyimide film and a sacrificial layer attached is placed in an organic solvent, the solvent gradually penetrates the sacrificial layer, causing it to swell. During the swelling stage, the interfacial adhesion of the sacrificial layer gradually decreases, and a small gap appears between the polyimide film and the silicon wafer. When the swelling reaches a certain extent, the sacrificial layer begins to dissolve, allowing the polyimide film to detach naturally. By appropriately adjusting the solvent temperature to regulate the swelling rate, tearing or damage to the polyimide film due to stress concentration can be avoided. The final result is a polyimide film with high integrity and no surface residue.
[0026] Beneficial Effects: Compared with traditional technologies such as laser peeling, the wet-release method for releasing polyimide films provided by this invention exhibits greater economic and process advantages. The wet process eliminates the need for expensive laser light sources and optical platforms, significantly reducing equipment investment and maintenance costs, making it suitable for large-scale deployment in flexible electronics manufacturing. Furthermore, since there is no localized high temperature during the release process, the polyimide film can completely avoid problems such as carbonization, microcracks, and dielectric degradation, thereby obtaining a high-quality film with intact structure, smooth surface, and stable performance.
[0027] In terms of process controllability and production efficiency, the demolding mechanism adopted in this invention is based on a controllable reaction between the solvent and the sacrificial layer material. It has a wide process window and is almost independent of sensitive parameters such as laser energy and absorbance, thus exhibiting higher stability and repeatability. This method supports simultaneous processing of multiple silicon wafers, enabling true mass production and significantly improving the large-scale production capacity of polyimide films, providing a reliable path for industrial mass production.
[0028] In terms of process adaptability, the method of this invention is applicable to polyimide films of varying thicknesses, with particular advantages in the complete transfer of ultrathin films. Furthermore, the method is compatible with patterned structures and multilayer composite film systems containing metal interconnect layers, making it suitable for various flexible electronic structures. Its basic principles can also be extended to other polymer film systems requiring high-temperature curing before release, demonstrating good versatility and scalability. Attached Figure Description
[0029] Figure 1 This is a flowchart of a wet-release method for releasing and demolding polyimide films, as described in an embodiment of the present invention. Detailed Implementation
[0030] The technical solutions in 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 following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use.
[0031] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values of the components and steps set forth in these embodiments do not limit the scope of the invention. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may include different values. It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.
[0032] The present invention will be further described below with reference to the embodiments.
[0033] In the following examples, the materials used were sourced as follows: polyimide (PI) was purchased from Asahi Kasei Corporation, model BL-301; polymethyl methacrylate (PMMA) was purchased from Nippon Kayaku Co., Ltd., models 495 PMMA A6 and 950 PMMAA4.
[0034] Example 1
[0035] This embodiment provides a wet-release method for releasing and demolding polyimide films, wherein the polyimide is a photosensitive polyimide; such as Figure 1 As shown, the method includes: The silicon wafers were cleaned with a mixture of concentrated sulfuric acid and hydrogen peroxide in a volume ratio of 3:1, and then treated with oxygen plasma. After oxygen plasma treatment, a surface oxide layer with Si-O bonds as the main component was formed on the surface of the silicon wafer, resulting in a silicon wafer with a hydrophilic surface. The wafers were then dried in a nitrogen atmosphere for later use. Using polymethyl methacrylate (PMMA) A6 (495 PMMA A6) as the sacrificial layer material, a polymethyl methacrylate solution was spin-coated onto the surface of a hydrophilically treated silicon wafer using a spin coater: first, the solution was spread at a low speed of 500 rpm for 5 seconds, followed by a high speed of 2000 rpm for 30 seconds to form a uniform film; then, the silicon wafer was placed on a hot plate at 180°C and baked for 90 seconds to evaporate the solvent and cure the sacrificial layer, resulting in a silicon wafer with a sacrificial layer. The cured sacrificial layer had a smooth surface and a thickness of 450 nm. Polyimide was spin-coated stepwise on the sacrificial layer at 1000 rpm for 10 s, 3600 rpm for 30 s, and 1500 rpm for 5 s, and pre-baked at 100°C for 4 minutes to form a uniform polyimide film with a thickness of 5 μm. The polyimide film was then patterned using a standard photolithography process, including exposure (exposure light source: 365 nm ultraviolet light, intensity: 200 mJ / cm²). 2 The process involves development and curing. The curing process uses a segmented temperature program control: the sample is placed in a nitrogen-protected environment for imidization reaction. The temperature is first raised from 25°C to 200°C within 30 minutes, and then kept at 200°C for 2 hours to achieve full curing. After the curing is completed, the sample is naturally cooled to room temperature in the furnace to obtain a silicon wafer with a polyimide film and a sacrificial layer attached to its surface. Optionally, further processing can be performed on the polyimide film, such as metal vapor deposition.
[0036] After the polyimide patterning and curing are completed, the entire silicon wafer is immersed in acetone at 50°C. The acetone gradually penetrates into the sacrificial layer, causing the sacrificial layer to swell. The sacrificial layer swells until a continuous separation interface is formed at the edge of the polyimide film. When the entire polyimide film separates from the silicon wafer under slight disturbance of the organic solvent, the polyimide film is released and demolded.
[0037] Example 2
[0038] This embodiment provides a wet-release method for releasing and demolding polyimide films, wherein the polyimide is a photosensitive polyimide; such as Figure 1 As shown, the method includes: The silicon wafers were cleaned with a mixture of concentrated sulfuric acid and hydrogen peroxide in a volume ratio of 3:1, and then treated with oxygen plasma. After oxygen plasma treatment, a surface oxide layer with Si-O bonds as the main component was formed on the surface of the silicon wafer, resulting in a silicon wafer with a hydrophilic surface. The wafers were then dried in a nitrogen atmosphere for later use. Polymethyl methacrylate (PMMA) A4 (950 PMMA A4) was used as the sacrificial layer material. The PMMA solution was spin-coated onto the hydrophilically treated silicon wafer surface using a spin coater: first, the solution was spread at a low speed of 500 rpm for 5 seconds, followed by a high speed of 2000 rpm for 30 seconds to form a uniform film. The silicon wafer was then placed on a hot plate at 180°C and baked for 90 seconds to evaporate the solvent and solidify the sacrificial layer, resulting in a silicon wafer with a sacrificial layer. The solidified sacrificial layer had a smooth surface and a thickness of 300 nm. Polyimide was spin-coated stepwise on the sacrificial layer at 1000 rpm for 10 s, 3600 rpm for 30 s, and 1500 rpm for 5 s, and pre-baked at 100°C for 4 minutes to form a uniform polyimide film with a thickness of 5 μm. The polyimide film was then patterned using a standard photolithography process, including exposure (exposure light source: 365 nm ultraviolet light, intensity: 200 mJ / cm²). 2 The process involves developing and curing the sample. The curing process is controlled by a segmented temperature program: the sample is placed in a nitrogen-protected environment for imidization reaction. The temperature is first raised from 25°C to 200°C within 30 minutes, and then kept at 200°C for 2 hours to achieve full curing. After the curing process, the sample is naturally cooled to room temperature in the furnace to obtain a silicon wafer with a polyimide film and a sacrificial layer attached to its surface. Optionally, further processing can be performed on the polyimide film, such as metal vapor deposition.
[0039] After the polyimide patterning and curing are completed, the entire silicon wafer is immersed in N-methylpyrrolidone at 60°C. N-methylpyrrolidone gradually penetrates into the sacrificial layer, causing the sacrificial layer to swell. The sacrificial layer swells until a continuous separation interface is formed at the edge of the polyimide film. When the polyimide film is completely separated from the silicon wafer under slight disturbance of the organic solvent, the polyimide film is released and demolded.
[0040] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.
Claims
1. A method for releasing and demolding polyimide films based on wet release, characterized in that, include: Silicon wafers are cleaned with concentrated sulfuric acid and hydrogen peroxide and treated with oxygen plasma to obtain silicon wafers with hydrophilic surfaces, which are then dried. A sacrificial layer material is coated onto a silicon wafer with a hydrophilic surface and then cured to obtain a silicon wafer with a sacrificial layer. Polyimide is spin-coated onto the sacrificial layer, and the polyimide film is patterned by photolithography and then cured to obtain a silicon wafer with a polyimide film and a sacrificial layer attached. The silicon wafer with the attached polyimide film and sacrificial layer is placed in an organic solvent and immersed. The sacrificial layer swells until a continuous separation interface is formed at the edge of the polyimide film. When the entire polyimide film separates from the silicon wafer under slight disturbance of the organic solvent, the polyimide film is released and demolded. The sacrificial layer material is a polymer material that swells or dissolves in an organic solvent and is resistant to the curing temperature of polyimide.
2. The method for releasing and demolding polyimide films based on wet release according to claim 1, characterized in that, The sacrificial layer material is polymethyl methacrylate; the polyimide is a photosensitive polyimide.
3. The method for releasing and demolding polyimide films based on wet release according to claim 1 or 2, characterized in that, The drying method for the silicon wafer with a hydrophilic surface includes drying it in a nitrogen atmosphere.
4. The method for releasing and demolding polyimide films based on wet release according to claim 1, characterized in that, The method for coating the sacrificial layer material includes: using a spin coater to spin coat the sacrificial layer material onto a silicon wafer with a hydrophilic surface at a low speed of 500-1000 rpm for 5-10 seconds, and then spin coating it at a high speed of 2000-4000 rpm for 30-60 seconds.
5. The method for releasing and demolding polyimide films based on wet release according to claim 1, characterized in that, The curing method for coating a sacrificial layer material on a silicon wafer with a hydrophilic surface includes: placing the silicon wafer coated with the sacrificial layer material on a hot plate at 150-200°C and baking it for 2-5 minutes.
6. The method for releasing and demolding polyimide films based on wet release according to claim 1, 4, or 5, characterized in that, The thickness of the sacrificial layer is 200-1000 nm.
7. The method for releasing and demolding polyimide films based on wet release according to claim 1, characterized in that, The spin-coating method for polyimide includes: spin coating at 1000-1200 rpm for 8-15 seconds, spin coating at 3500-4000 rpm for 25-35 seconds, and spin coating at 1500-2000 rpm for 5-8 seconds.
8. The method for releasing and demolding polyimide films based on wet release according to claim 1, characterized in that, The thickness of the polyimide film formed on the sacrificial layer is 2-50 μm.
9. The method for releasing and demolding polyimide films based on wet release according to claim 1, characterized in that, The curing process of the polyimide film adopts segmented temperature control: first, the solvent is removed in an environment of 80-120℃ for 4-5 minutes, then imidization reaction is carried out in a nitrogen environment at 150-200℃, and finally, it is completely cured in an environment of 200-280℃ for 2-2.5 hours.
10. The method for releasing and demolding polyimide films based on wet release according to claim 1, characterized in that, The organic solvent is acetone or N-methylpyrrolidone; Using acetone as an organic solvent, the process of placing the silicon wafer with the attached polyimide film and sacrificial layer in the organic solvent further includes adjusting the temperature of the organic solvent to 50-55°C. Using N-methylpyrrolidone as an organic solvent, the process of placing the silicon wafer with the attached polyimide film and sacrificial layer in the organic solvent further includes adjusting the temperature of the organic solvent to 50-60°C.