Flexible PI evaporation mask and preparation method thereof

Abstract

This invention discloses a flexible polyimide (PI) evaporation mask and its preparation method, belonging to the field of evaporation mask preparation technology. In this invention, an aluminum or aluminum alloy sacrificial layer is used as the sacrificial layer for the polyimide (PI) mask, and the PI mask can be efficiently released using an aluminum etching solution. This fundamentally avoids the irreversible substrate damage caused by hydrofluoric acid etching of the silicon substrate. After release, the structural integrity of the silicon wafer remains unaffected, allowing for repeated use. This invention effectively reduces silicon substrate material consumption, significantly lowers substrate consumable costs in mass production, and greatly improves the economics of industrial production.

Description

Technical Field

[0001] This invention belongs to the field of vapor deposition mask preparation technology, specifically relating to a flexible PI vapor deposition mask and its preparation method. Background Technology

[0002] In the field of electronic device manufacturing, patterning for film deposition is one of the core processes for achieving functional and refined devices. The mask, as a key component in this process, directly determines the accuracy, edge quality, and processing efficiency of the deposition pattern, and has a decisive impact on the overall performance and reliability of electronic devices. With the rapid development of flexible electronics, micro-nano optoelectronic devices, and 3D integrated circuit technology, electronic device structures are evolving towards miniaturization, complexity, curvature, and flexibility, placing higher demands on the patterning capabilities of evaporation processes. Especially when performing precise patterning on substrates with special complex structures (such as curved surfaces, irregular shapes, and bendable surfaces), traditional rigid metal masks lack flexible deformation capabilities and cannot conformally fit with complex curved surfaces, resulting in significant shadowing effects and pattern deviations during evaporation, severely restricting the fabrication of high-precision, high-fidelity thin film patterns.

[0003] To overcome the limitations of rigid masks, flexible mask technology based on polymer materials has emerged. Polyimide (PI) has become an ideal substrate material for fabricating flexible masks due to its excellent high-temperature resistance (glass transition temperature is typically above 300°C), good chemical stability, low dielectric constant, and tunable mechanical flexibility. Existing technologies already include flexible mask fabrication schemes based on polyimide. For example, patent application CN101566799A discloses a method for fabricating a perforated polyimide evaporation mask. Using a single-crystal silicon wafer as a temporary support substrate, a polyimide precursor layer and a Cr / Au / Al metal barrier layer are sequentially fabricated. A perforated pattern is formed in the polyimide layer using photolithography and reactive ion etching (RIE) processes. Finally, the silicon substrate is removed using wet etching with hydrofluoric acid (HF) solution, and the metal barrier layer is removed using a removal solution to obtain a flexible polyimide mask. This method achieves flexible mask fabrication to a certain extent and can be used for evaporation patterning of complex substrate structures. However, this technical solution has the following core technical defects. First, it uses hydrofluoric acid wet chemical etching of a single-crystal silicon substrate to release the polyimide mask. Because hydrofluoric acid has isotropic etching properties on silicon, the etching process completely destroys the surface morphology and crystal structure of the silicon substrate, making it unusable. Considering the high cost of single-crystal silicon and the difficulty in obtaining large-size, high-flatness silicon wafers, this single-use strategy results in significant raw material waste, greatly increasing the unit manufacturing cost of the flexible mask and hindering large-scale production. Second, the metal barrier layer used for pattern transfer and the silicon used to release the flexible mask use completely different material systems. Their removal requires separate wet chemical etching to remove the metal barrier layer and hydrofluoric acid etching to remove the silicon substrate, making process integration and simultaneous removal impossible. This step-by-step, material-specific processing strategy leads to a lengthy process flow, high equipment occupancy, difficulty in controlling the process window, and increased risk of cross-contamination between different etching steps, significantly increasing overall processing complexity and manufacturing costs. Summary of the Invention

[0004] To address the above problems, the purpose of this invention is to provide a flexible PI evaporation mask and its preparation method.

[0005] In a first aspect, the present invention provides a method for preparing a flexible PI vapor deposition mask, comprising the following steps: S1. An aluminum or aluminum alloy sacrificial layer is deposited on a silicon wafer. Then, a PI layer is coated on the aluminum or aluminum alloy sacrificial layer. After drying and imidization, an intermediate device with a PI film on the surface is obtained. S2. Deposit an aluminum or aluminum alloy mask layer on the PI film of the intermediate device with a PI film as the surface layer to obtain the intermediate device 2 with an aluminum or aluminum alloy mask layer as the surface layer. S3. Photoresist is spin-coated onto the aluminum or aluminum alloy mask layer of the intermediate device 2, which has an aluminum or aluminum alloy mask layer on the surface, to obtain a photoresist layer. After exposure and development, the photoresist layer forms a photoresist pattern. Using the photoresist pattern as a mask, the aluminum or aluminum alloy mask layer is etched. After etching, the photoresist is removed to obtain a patterned aluminum or aluminum alloy mask layer. Using the patterned aluminum or aluminum alloy mask layer as a mask, the PI film is etched to form a PI mask with the target pattern, thus obtaining the intermediate device 3. S4. The intermediate device 3 is placed in an etching solution for etching to remove the aluminum or aluminum alloy sacrificial layer and the patterned aluminum or aluminum alloy mask layer, while separating the PI mask from the silicon wafer. The separated PI mask is taken out, cleaned, and dried to obtain a flexible PI vapor deposition mask. The silicon wafer is taken out, cleaned, and dried, and then reused for the preparation of flexible PI vapor deposition masks.

[0006] Secondly, the present invention provides a flexible PI evaporation mask prepared using the aforementioned preparation method.

[0007] Thirdly, the flexible PI evaporation mask provided by the present invention is used to deposit metal layers on irregularly shaped substrates.

[0008] Compared with the prior art, one or more of the above technical solutions can achieve at least one of the following beneficial effects: (1) In the method of the present invention, an aluminum or aluminum alloy sacrificial layer is used as the sacrificial layer of the PI mask. The PI mask can be efficiently released by the etching solution, which fundamentally avoids irreversible damage to the substrate caused by hydrofluoric acid etching of the silicon substrate. The integrity of the silicon wafer structure after release is not affected, and it can be reused multiple times, effectively reducing the waste of silicon substrate materials, significantly reducing the cost of substrate consumables in mass production, realizing the reuse of silicon wafers and improving industrial economy.

[0009] (2) In this invention, the aluminum or aluminum alloy sacrificial layer and the aluminum or aluminum alloy mask layer are respectively used as the sacrificial layer and the hard mask plate layer. The aluminum or aluminum alloy material is relatively cheap, which can reduce the material cost. Moreover, the aluminum or aluminum alloy sacrificial layer and the aluminum or aluminum alloy mask layer can be removed at the same time, and the PI mask can be released at the same time. This eliminates the extra precious metal mask removal step in the existing process, effectively simplifies the overall process flow, improves production efficiency and reduces the difficulty of process control.

[0010] (3) The core materials selected in this invention, such as silicon wafers, aluminum, aluminum alloys, and PI, are all conventional and mature materials in the semiconductor processing field. They are easy to obtain and cost-controllable. Key processes such as aluminum deposition, aluminum etching, PI spin coating, and PI imidization can be perfectly adapted to existing conventional semiconductor processing equipment. No new special production equipment is required. The process compatibility is strong, and it can be quickly connected to existing industrial production lines, which is convenient for large-scale mass production. Attached Figure Description

[0011] Figure 1 This is a process flow diagram of the present invention. Detailed Implementation

[0012] To facilitate understanding of the present invention, the invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0013] As mentioned above, in a first aspect, the present invention provides a method for preparing a flexible PI vapor deposition mask, comprising the following steps: S1. An aluminum or aluminum alloy sacrificial layer is deposited on a silicon wafer. Then, a PI layer is coated on the aluminum or aluminum alloy sacrificial layer. After drying and imidization, an intermediate device with a PI film on the surface is obtained. S2. Deposit an aluminum or aluminum alloy mask layer on the PI film of the intermediate device with a PI film as the surface layer to obtain the intermediate device 2 with an aluminum or aluminum alloy mask layer as the surface layer. S3. Photoresist is spin-coated onto the aluminum or aluminum alloy mask layer of the intermediate device 2, which has an aluminum or aluminum alloy mask layer on the surface, to obtain a photoresist layer. After exposure and development, the photoresist layer forms a photoresist pattern. Using the photoresist pattern as a mask, the aluminum or aluminum alloy mask layer is etched. After etching, the photoresist is removed to obtain a patterned aluminum or aluminum alloy mask layer. Using the patterned aluminum or aluminum alloy mask layer as a mask, the PI film is etched to form a PI mask with the target pattern, thus obtaining the intermediate device 3. S4. The intermediate device 3 is placed in an etching solution for etching to remove the aluminum or aluminum alloy sacrificial layer and the patterned aluminum or aluminum alloy mask layer, while separating the PI mask from the silicon wafer. After the PI mask is removed, it is cleaned and dried to obtain a flexible PI vapor deposition mask. After the silicon wafer is removed, it is cleaned and dried, and it is reused for the preparation of flexible PI vapor deposition masks.

[0014] The method of this invention enables the reuse of silicon wafers, significantly reducing production costs: This invention uses an aluminum or aluminum alloy sacrificial layer as the sacrificial layer for the PI mask, and the PI mask can be efficiently released through an etching solution, fundamentally avoiding the irreversible damage to the substrate caused by etching the silicon substrate with hydrofluoric acid; the structural integrity of the released silicon wafer is not affected, and it can be reused multiple times, effectively reducing the waste of silicon substrate materials, significantly reducing the cost of substrate consumables in the mass production process, and improving industrial economics.

[0015] The method of this invention can reduce the consumption of precious metals and simplify the process flow: In this invention, the aluminum or aluminum alloy sacrificial layer and the aluminum or aluminum alloy mask layer serve as the sacrificial layer and the hard mask layer, respectively. Aluminum or aluminum alloy materials are relatively inexpensive, which can reduce the material cost. Moreover, the aluminum or aluminum alloy sacrificial layer and the aluminum or aluminum alloy mask layer can be removed simultaneously, and the PI mask can be released. This eliminates the extra metal mask removal step in the existing process, effectively simplifying the overall process flow, improving production efficiency, and reducing the difficulty of process control.

[0016] The method of this invention has strong compatibility and is easy to implement: the core materials selected in this invention, such as silicon wafers, Al, Al alloys, and PI, are all conventional and mature materials in the semiconductor processing field, which are easy to obtain and have controllable costs; at the same time, the key processes such as Al deposition, Al etching, PI spin coating, and PI imidization can be perfectly adapted to existing conventional semiconductor processing equipment without the need for additional special production equipment. The process compatibility is strong, and it can be quickly connected to existing industrial production lines, which is convenient for large-scale mass production.

[0017] The process of this invention is environmentally friendly and energy-saving, and improves resource utilization: This invention effectively reduces the generation of silicon substrate waste by reusing silicon wafers; in addition, the simplification of the process flow further reduces energy consumption and the amount of chemical reagents used in the production process, taking into account both environmental protection and economy, and improving the sustainable development capability of the industry.

[0018] In some embodiments, in step S1, the silicon wafer is selected as a silicon wafer with a (100) crystal orientation.

[0019] In some embodiments, in step S1, the thickness of the aluminum or aluminum alloy sacrificial layer is 0.5~2μm, including but not limited to: 0.5μm, 0.8μm, 1μm, 1.2μm, 1.5μm, 1.8μm, 2μm, etc.

[0020] In this invention, adjusting the thickness of the aluminum or aluminum alloy sacrificial layer can ensure sufficient resistance to etching while facilitating subsequent corrosion removal and ensuring the accuracy of the PI vapor deposition mask.

[0021] In some embodiments, in step S1, the coating is selected from spin coating and spray coating; more preferably, spin coating is used, and the spin coating speed is 1500~3000 r / min, including but not limited to: 1500 r / min, 1800 r / min, 2000 r / min, 2200 r / min, 2500 r / min, 2800 r / min, 3000 r / min, etc.

[0022] In some embodiments, in step S1, the drying temperature is 90~110℃, including but not limited to: 90℃, 95℃, 100℃, 105℃, 110℃, etc.; the drying time is 20~40min, including but not limited to: 20min, 25min, 30min, 35min, 40min, etc.

[0023] In some embodiments, the heating program for the imidization treatment in step S1 is as follows: heating to 70~90℃ (including but not limited to: 70℃, 75℃, 80℃, 85℃, 90℃, etc.), holding at this temperature for 20~40 min (including but not limited to: 20 min, 25 min, 30 min, 35 min, 40 min, etc.), then heating to 130~150℃ (including but not limited to: 130℃, 135℃, 140℃, 145℃, 150℃, etc.), and holding at this temperature for 50~70 min (including but not limited to: 50 min, 55 min, 60 min, 65 min, etc.). (e.g., 70 min); then raise the temperature to 210~230℃ (including but not limited to: 210℃, 215℃, 220℃, 225℃, 230℃, etc.), hold for 50~70 min (including but not limited to: 50 min, 55 min, 60 min, 65 min, 70 min, etc.); then raise the temperature to 310~330℃ (including but not limited to: 310℃, 315℃, 320℃, 325℃, 330℃, etc.), hold for 50~70 min (including but not limited to: 50 min, 55 min, 60 min, 65 min, 70 min, etc.).

[0024] In some embodiments, in step S1, a tackifier is first applied before coating a layer of PI, and then a layer of PI is applied on the tackifier.

[0025] In this invention, by coating with a tackifier, the bonding strength between the PI layer and the aluminum or aluminum alloy sacrificial layer can be increased.

[0026] In some embodiments, the coating thickness of the tackifier is less than 200 nm, and the tackifier is a compound of 1-methoxy-2-propanol and a silane coupling agent.

[0027] In some embodiments, in step S1, the thickness of the PI film is 2~5μm, including but not limited to: 2μm, 3μm, 4μm, 5μm, etc.

[0028] In this invention, by controlling the thickness of the PI film layer, the prepared flexible PI mask can have both flexibility and strength, and can be bonded to complex structure substrates while ensuring pattern accuracy.

[0029] In some embodiments, in steps S1 and S2, the aluminum alloy is independently selected from aluminum-copper alloy and aluminum-silicon alloy.

[0030] In some embodiments, in steps S1 and S2, the methods for depositing the aluminum or aluminum alloy sacrificial layer and the method for depositing the aluminum or aluminum alloy mask layer are each independently selected from one of magnetron sputtering, chemical vapor deposition, atomic layer deposition, and evaporation; more preferably, magnetron sputtering is used, and the process parameters of magnetron sputtering are: the power of magnetron sputtering is 3~5kW, including but not limited to: 3kW, 3.5kW, 4kW, 4.5kW, 5kW, etc.; the Ar gas flow rate is 50~100sccm, including but not limited to: 50sccm, 60sccm, 70sccm, 80sccm, 90sccm, 100sccm, etc.

[0031] In some embodiments, in step S2, the thickness of the aluminum or aluminum alloy mask layer is 0.5~1μm, including but not limited to: 0.5μm, 0.6μm, 0.7μm, 0.8μm, 0.9μm, 1.0μm, etc.

[0032] In some embodiments, in step S3, the etching process for etching the aluminum or aluminum alloy mask layer is dry etching or wet etching; more preferably, it is dry etching, and the process parameters for dry etching are as follows: the etching gas is a mixture of Cl2 and BCl3 in a volume ratio of (2~5):1, and the volume ratio includes, but is not limited to, 2:1, 3:1, 4:1, 5:1, etc.; the etching power is 80~150W, including but not limited to, 80W, 90W, 100W, 110W, 120W, 130W, 140W, 150W, etc.; the etching time is 20~40s, including but not limited to, 20s, 25s, 30s, 35s, 40s, etc.

[0033] In some embodiments, in step S3, the etching process for etching the PI film is reactive ion etching. The reactive ion etching process involves an etching gas mixture of O2 and CF4 in a volume ratio of (800~1200):(10~20), where the volume ratio includes, but is not limited to, 800:10, 1000:10, 1200:10, 800:15, 1000:15, 1200:15, 800:20, 1000:20, 1200:20, etc. The power is 800~1000W, including but not limited to: 800W, 850W, 900W, 950W, 1000W, etc.; the etching pressure is 0.5~2 torr, more preferably 0.5~1 torr; the etching temperature is 40~60℃, including but not limited to: 40℃, 45℃, 50℃, 55℃, 65℃, etc.; the etching time is 8~12min, including but not limited to: 8min, 9min, 10min, 11min, 12min, etc.

[0034] In some embodiments, in step S3, the spin coating speed is 1500~3000 r / min, including but not limited to: 1500 r / min, 1800 r / min, 2000 r / min, 2200 r / min, 2500 r / min, 2800 r / min, 3000 r / min, etc.; the thickness of the photoresist layer is 1.5~3 μm, including but not limited to: 1.5 μm, 2 μm, 2.5 μm, 3 μm, etc.

[0035] In some embodiments, in step S4, the etching solution is an aluminum metal etching solution, which is a mixture of phosphoric acid, nitric acid, acetic acid, and water in a volume ratio of (7.8~8.2):(0.8~1.2):(0.8~1.2):(1.8~2.2). The volume ratio includes, but is not limited to: 7.8:0.8:0.8:1.8, 7.8:1:1:2, 7.8:1.2:1.2:2.2, 8:0.8:0.8:1.8, 8:1:1:2, 8:1.2:1.2:2.2, 8.2:0.8:0.8:1.8, 8.2:1:1:2, 8.2:1.2:1.2:2.2, etc.; wherein: the concentration of phosphoric acid is 82~85wt%, the concentration of nitric acid is 68~72wt%, and the acetic acid is pure acetic acid.

[0036] In some embodiments, in step S4, the corrosion temperature is 35~45℃, including but not limited to: 35℃, 38℃, 40℃, 42℃, 45℃, etc., and the corrosion time is 30~120min, including but not limited to: 30min, 40min, 50min, 60min, 70min, 80min, 90min, 100min, 110min, 120min, etc., and more preferably 50~100min.

[0037] Secondly, the present invention provides a flexible PI evaporation mask prepared using the aforementioned preparation method.

[0038] Thirdly, the flexible PI evaporation mask provided by the present invention is used to deposit metal layers on irregularly shaped substrates.

[0039] The flexible PI evaporation mask prepared by this invention has excellent performance and is suitable for complex substrate structures. The PI mask prepared by the method of this invention has good flexibility, high temperature resistance and pattern accuracy. The lateral etching amount during processing is small, the mask pattern edge is neat and burr-free, and it can be closely attached to the surface of various special complex structures (irregular shape, curved surface). It effectively solves the technical problem that traditional rigid masks cannot be attached to complex substrates and the coating deviation is large. It ensures the accuracy of coating pattern processing and meets the needs of electronic devices to develop towards miniaturization, complexity and flexibility.

[0040] The process flow diagram for fabricating the flexible PI vapor deposition mask in this invention is as follows: Figure 1 As shown, the specific steps can be found in the embodiments.

[0041] The tackifier used in the embodiments of the present invention is a compound of 1-methoxy-2-propanol and silane coupling agent.

[0042] Example 1 S1. Pretreatment of silicon wafer substrate: Select a silicon wafer with (100) crystal orientation and a thickness of 600μm, and clean it sequentially using the standard RCA cleaning process to remove surface oil, oxide layer and metal particles, so as to obtain a clean and flat silicon wafer substrate.

[0043] S2. Preparation of the first aluminum film layer: An Al film is deposited on the surface of a silicon wafer substrate using a magnetron sputtering process, wherein: the magnetron sputtering power is 4kW, the sputtering time is 5min, the Ar gas flow rate is 80sccm, and the deposition temperature is room temperature, resulting in a first aluminum film layer with a thickness of 1.0μm, which serves as a sacrificial layer for PI release.

[0044] S3. Preparation of PI film: A tackifier was spin-coated onto the first aluminum film at a spin speed of 1800 r / min for 40 s, with a tackifier thickness of <200 nm. Then, a PI solution was spin-coated onto the tackifier at a spin speed of 2500 r / min, with a spin coating thickness of 7 μm. After spin coating, the film was dried at 100 °C for 30 min, followed by imidization curing. The imidization curing temperature program was as follows: heated to 80 °C and held for 30 min, then heated to 140 °C and held for 60 min, then heated to 220 °C and held for 60 min, and finally heated to 320 °C and held for 60 min, resulting in a PI film with a thickness of 3.2 μm.

[0045] S4. Preparation of the second aluminum film layer: An Al film layer is deposited on the surface of the PI film layer by magnetron sputtering, wherein: the magnetron sputtering power is 4kW, the sputtering time is 4min, the Ar gas flow rate is 80sccm, the deposition temperature is room temperature, and a second aluminum film layer with a thickness of 0.8μm is obtained; the second aluminum film layer is used as a mask for etching the PI film layer.

[0046] S5. Patterning of the second aluminum film layer: Positive photoresist is spin-coated onto the surface of the second aluminum film layer at a spin speed of 2500 r / min for 40 s, resulting in a photoresist layer thickness of 2 μm. Then, it is pre-baked in a hot plate at 110℃ for 65 s. After optical exposure for 20 s using a photolithography machine, it is developed in a developer for 50 s to form a photoresist pattern matching the target PI mask pattern. Using the photoresist pattern as a mask, the second aluminum film layer is etched using a dry etching process. The etching gas is a mixture of Cl2 and BCl3 in a volume ratio of 3.5:1, with an etching power of 120 W and an etching time of 30 s. After etching, the photoresist layer is removed to obtain the patterned second aluminum film layer.

[0047] S6. PI film patterning: Using the patterned second aluminum film as a mask, reactive ion etching is used to etch the PI film, wherein: the etching power is 900W, the O2 flow rate is 1000sccm, the CF4 flow rate is 15sccm, the pressure is 0.5~1Torr, the etching temperature is 50℃, and the etching time is 10min; the first aluminum film is etched until the patterned part is completely exposed, and the patterned PI film is obtained.

[0048] S7. Aluminum film removal and PI mask peeling: The device obtained in step S6 is placed in an Al etching solution (the Al etching solution is a mixture of 85wt% phosphoric acid, 70wt% nitric acid, acetic acid and deionized water in a volume ratio of 8:1:1:2), and the etching temperature is controlled at 40℃ for 50min. During the etching process, the two aluminum films are completely etched away, and the PI mask is separated from the Si wafer. After etching, the PI mask is rinsed with deionized water 3 times for 5~10min each time, and then placed in an oven at 80~100℃ to dry for 20min to obtain a flexible PI vapor-deposited mask.

[0049] S8. Silicon Wafer Recycling and Reuse: After the PI mask is released, the silicon wafer undergoes standard RCA cleaning to remove surface oil, oxide layer, and metal particles, resulting in a clean and flat silicon wafer substrate. Steps S1-S7 are repeated for the next batch of flexible PI evaporation masks. Testing shows that this Si wafer can be reused at least 20 times without affecting the pattern accuracy and release effect of subsequent flexible PI evaporation masks.

[0050] Comparative Example 1 The process is basically the same as in Example 1, except that step S2 is omitted, and a PI film layer is directly prepared on the wafer surface. The specific steps are as follows: S1, same as step S1 in Example 1.

[0051] S2, same as step S3 in Example 1.

[0052] S3, same as step S4 in Example 1.

[0053] S4, same as step S5 in Example 1.

[0054] S5. Aluminum film removal: The device obtained in step S4 is placed in an Al etching solution (the Al etching solution is a mixture of 85wt% phosphoric acid, 70wt% nitric acid, acetic acid and deionized water in a volume ratio of 8:1:1:2), and the etching temperature is controlled at 40℃ and the etching time is 50min; during the etching process, the aluminum film is completely etched away, and a silicon wafer containing a PI mask is obtained.

[0055] S6. Release of the PI film: The silicon wafer containing the PI mask is placed in a hydrofluoric acid etching solution (hydrofluoric acid etching solution ratio is HF (50wt%):HNO3 (70wt%):acetic acid = 12:1:2) and etched at room temperature for 10 minutes to release the PI film, thus obtaining the PI mask. In this step S6, the silicon wafer is severely etched and cannot be reused.

[0056] Example 2 S1. Pretreatment of silicon wafer substrate: Select a silicon wafer with (100) crystal orientation and a thickness of 500μm, and clean it sequentially using the standard RCA cleaning process to remove surface oil, oxide layer and metal particles, so as to obtain a clean and flat silicon wafer substrate.

[0057] S2. Preparation of the first aluminum film layer: An Al film is deposited on the surface of a silicon wafer substrate using a magnetron sputtering process, wherein: the magnetron sputtering power is 3kW, the sputtering time is 12min, the Ar gas flow rate is 50sccm, and the deposition temperature is room temperature, resulting in a first aluminum film layer with a thickness of 2μm, which serves as a sacrificial layer for PI release.

[0058] S3. Preparation of PI film: A tackifier is spin-coated onto the first aluminum film at a spin speed of 1500 r / min for 40 s, with a tackifier thickness of <200 nm. Then, a PI solution is spin-coated onto the tackifier at a spin speed of 1500 r / min for a thickness of 5 μm. After spin-coating, the film is dried at 90 °C for 40 min, followed by imidization curing. The imidization curing temperature program is as follows: heat to 70 °C and hold for 40 min, then heat to 130 °C and hold for 70 min, then heat to 210 °C and hold for 70 min, then heat to 310 °C and hold for 70 min. A PI film with a thickness of 2.5 μm is obtained.

[0059] S4. Preparation of the second aluminum film layer: An Al film is deposited on the surface of the PI thin film layer using a magnetron sputtering process, wherein: the magnetron sputtering power is 3kW, the sputtering time is 3min, the Ar gas flow rate is 50sccm, and the deposition temperature is room temperature, resulting in a second aluminum film layer with a thickness of 0.5μm; the second aluminum film layer serves as a mask for etching the PI film layer.

[0060] S5. Patterning of the second aluminum film layer: Positive photoresist is spin-coated onto the surface of the second aluminum film layer at a spin speed of 3000 r / min for 40 s, resulting in a photoresist layer thickness of 1.5 μm. Then, it is pre-baked in a hot plate at 110℃ for 65 s. Optical exposure is performed using a photolithography machine for 20 s, followed by development in a developer for 50 s to form a photoresist pattern matching the target PI mask pattern. Using the photoresist pattern as a mask, the second aluminum film layer is etched using a dry etching process. The etching gas is a mixture of Cl2 and BCl3 in a volume ratio of 5:1, with an etching power of 80 W and an etching time of 20 s. After etching, the photoresist layer is removed to obtain the patterned second aluminum film layer.

[0061] S6. PI film patterning: Using the patterned second aluminum film as a mask, reactive ion etching is used to etch the PI film, wherein: the etching power is 800W, the O2 flow rate is 800sccm, the CF4 flow rate is 10sccm, the pressure is 0.5~1Torr, the etching temperature is 40℃, and the etching time is 8min; the first aluminum film is etched until the patterned part is completely exposed, and the patterned PI film is obtained.

[0062] S7. Aluminum film removal and PI mask release: The device obtained in step S6 is placed in an Al etching solution (the Al etching solution is a mixture of 85wt% phosphoric acid, 72wt% nitric acid, acetic acid and deionized water in a volume ratio of 8.2:1.2:1.2:2.2). The etching temperature is controlled at 45℃ and the etching time is 50min. During the etching process, the two aluminum films are completely etched away, and the PI mask is separated from the Si wafer. After etching, the PI mask is rinsed with deionized water 3 times, each time for 5~10min, and then placed in an oven at 80~100℃ to dry for 20min to obtain a flexible PI vapor-deposited mask.

[0063] S8. Silicon Wafer Recycling and Reuse: After the PI mask is released, the silicon wafer undergoes standard RCA cleaning to remove surface oil, oxide layer, and metal particles, resulting in a clean and flat silicon wafer substrate. Steps S1-S7 are repeated for the next batch of flexible PI evaporation masks. Testing shows that this Si wafer can be reused at least 20 times without affecting the pattern accuracy and release effect of subsequent flexible PI evaporation masks.

[0064] Example 3 S1. Pretreatment of silicon wafer substrate: Select a silicon wafer with (100) crystal orientation and a thickness of 500μm, and clean it sequentially using the standard RCA cleaning process to remove surface oil, oxide layer and metal particles, so as to obtain a clean and flat silicon wafer substrate.

[0065] S2. Preparation of the first aluminum film layer: An Al film is deposited on the surface of a silicon wafer substrate using a magnetron sputtering process, wherein: the magnetron sputtering power is 5kW, the sputtering time is 3min, the Ar gas flow rate is 100sccm, and the deposition temperature is room temperature, resulting in a first aluminum film layer with a thickness of 0.5μm, which serves as a sacrificial layer for PI release.

[0066] S3. Preparation of PI film: A tackifier is spin-coated onto the first aluminum film at a spin speed of 2000 r / min for 40 s, with a tackifier thickness of <200 nm. Then, a PI solution is spin-coated onto the tackifier at a spin speed of 3000 r / min, with a spin coating thickness of 10 μm. After spin coating, the film is dried at 110 °C for 20 min, followed by imidization curing. The imidization curing temperature program is as follows: heat to 90 °C and hold for 20 min, then heat to 150 °C and hold for 50 min, then heat to 230 °C and hold for 50 min, then heat to 330 °C and hold for 50 min, resulting in a PI film with a thickness of 5 μm.

[0067] S4. Preparation of the second aluminum film layer: An Al film is deposited on the surface of the PI thin film layer using a magnetron sputtering process, wherein: the magnetron sputtering power is 5kW, the sputtering time is 6min, the Ar gas flow rate is 100sccm, and the deposition temperature is room temperature, resulting in a second aluminum film layer with a thickness of 1.0μm; the second aluminum film layer serves as a mask for etching the PI film layer.

[0068] S5. Patterning of the second aluminum film layer: Positive photoresist is spin-coated onto the surface of the second aluminum film layer at a spin speed of 1500 r / min for 40 s, resulting in a photoresist layer thickness of 3 μm. Then, it is pre-baked in a hot plate at 110℃ for 80 s. After optical exposure for 20 s using a photolithography machine, it is developed in a developer for 60 s to form a photoresist pattern matching the target PI mask pattern. Using the photoresist pattern as a mask, the second aluminum film layer is etched using a dry etching process. The etching gas is a mixture of Cl2 and BCl3 in a volume ratio of 2:1, with an etching power of 150 W and an etching time of 40 s. After etching, the photoresist layer is removed to obtain the patterned second aluminum film layer.

[0069] S6. PI film patterning: Using the patterned second aluminum film as a mask, reactive ion etching is used to etch the PI film, wherein: the etching power is 1000W, the O2 flow rate is 1200sccm, the CF4 flow rate is 20sccm, the pressure is 0.5~1Torr, the etching temperature is 60℃, and the etching time is 12min; the first aluminum film is etched until the patterned part is completely exposed, and the patterned PI film is obtained.

[0070] S7. Aluminum film removal and PI mask release: The device obtained in step S6 is placed in an Al etching solution (the Al etching solution is a mixture of 83wt% phosphoric acid, 68wt% nitric acid, acetic acid and deionized water in a volume ratio of 7.8:0.8:0.8:1.8), and the etching temperature is controlled at 35℃ for 100min. During the etching process, the two aluminum films are completely etched away, and the PI mask is separated from the Si wafer. After etching, the PI mask is rinsed with deionized water 3 times for 5-10min each time, and then placed in an oven at 80-100℃ to dry for 20min to obtain a flexible PI vapor-deposited mask.

[0071] S8. Silicon Wafer Recycling and Reuse: After the PI mask is released, the silicon wafer undergoes standard RCA cleaning to remove surface oil, oxide layer, and metal particles, resulting in a clean and flat silicon wafer substrate. Steps S1-S7 are repeated for the next batch of flexible PI evaporation masks. Testing shows that this Si wafer can be reused at least 20 times without affecting the pattern accuracy and release effect of subsequent flexible PI evaporation masks.

[0072] The flexible PI evaporation masks prepared in Examples 1-3 and Comparative Example 1 were used for Cr / Au evaporation on irregularly shaped substrates. The specific operation steps are as follows: The flexible PI evaporation mask was attached to the surface of the curved irregularly shaped substrate, ensuring that the mask was in close contact with the substrate; using the PI evaporation mask as a shield, Cr was first evaporated, followed by Au evaporation. After evaporation, the PI evaporation mask was removed to obtain the Cr / Au pattern. The accuracy of the Cr / Au pattern formed on the curved substrate was observed and measured using a 3D laser confocal microscope. The test results are shown in Table 1.

[0073] Table 1 As shown in Table 1, the flexible PI evaporation mask prepared using the method of Example 1 has a precision comparable to that of the flexible PI evaporation mask prepared in Comparative Example 1. Furthermore, because the silicon wafer can be reused multiple times, the preparation cost of Example 1 is reduced by more than 60% compared to Comparative Example 1. Adjustments to the process parameters in Examples 2 and 3, within feasible ranges, resulted in virtually no impact on the pattern precision of the obtained products, with only minor fluctuations in preparation cost.

[0074] 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 principle 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 preparing a flexible PI vapor deposition mask, characterized in that, Includes the following steps: S1. An aluminum or aluminum alloy sacrificial layer is deposited on a silicon wafer. Then, a PI layer is coated on the aluminum or aluminum alloy sacrificial layer. After drying and imidization, an intermediate device with a PI film on the surface is obtained. S2. Deposit an aluminum or aluminum alloy mask layer on the PI film of the intermediate device with a PI film as the surface layer to obtain the intermediate device 2 with an aluminum or aluminum alloy mask layer as the surface layer. S3. Photoresist is spin-coated onto the aluminum or aluminum alloy mask layer of the intermediate device 2, which has an aluminum or aluminum alloy mask layer on the surface, to obtain a photoresist layer. After exposure and development, the photoresist layer forms a photoresist pattern. Using the photoresist pattern as a mask, the aluminum or aluminum alloy mask layer is etched. After etching, the photoresist is removed to obtain a patterned aluminum or aluminum alloy mask layer. Using a patterned aluminum or aluminum alloy mask layer as a mask, the PI film is etched to form a PI mask with the target pattern, thus obtaining the intermediate device 3; S4. The intermediate device 3 is placed in an etching solution for etching to remove the aluminum or aluminum alloy sacrificial layer and the patterned aluminum or aluminum alloy mask layer, while separating the PI mask from the silicon wafer. The separated PI mask is taken out, cleaned, and dried to obtain a flexible PI vapor deposition mask. The silicon wafer is taken out, cleaned, and dried, and then reused for the preparation of flexible PI vapor deposition masks.

2. The method for preparing the flexible PI vapor deposition mask according to claim 1, characterized in that, In step S1, the silicon wafer selected is a (100) oriented silicon wafer; And / or: The thickness of the aluminum or aluminum alloy sacrificial layer is 0.5~2μm; And / or: The thickness of the PI film is 2~5μm.

3. The method for preparing the flexible PI vapor deposition mask according to claim 1, characterized in that, In step S1, the coating is selected from spin coating and spray coating; And / or: The drying temperature is 90~110℃, and the drying time is 20~40min; And / or: The temperature program for imidization treatment is as follows: heat to 70~90℃, hold for 20~40 min, then heat to 130~150℃, hold for 50~70 min; then heat to 210~230℃, hold for 50~70 min; then heat to 310~330℃, hold for 50~70 min.

4. The method for preparing the flexible PI vapor deposition mask according to claim 1, characterized in that, In step S1, before coating a layer of PI, a layer of tackifier is first coated; wherein: the coating thickness of the tackifier is less than 200 nm, and the tackifier is composed of 1-methoxy-2-propanol and silane coupling agent.

5. The method for preparing the flexible PI vapor deposition mask according to claim 1, characterized in that, In steps S1 and S2, the aluminum alloy is independently selected from either aluminum-copper alloy or aluminum-silicon alloy. And / or: The methods for depositing the aluminum or aluminum alloy sacrificial layer and the methods for depositing the aluminum or aluminum alloy mask layer are each independently selected from one of magnetron sputtering, chemical vapor deposition, atomic layer deposition, and evaporation.

6. The method for preparing the flexible PI vapor deposition mask according to claim 1, characterized in that, In step S2, the thickness of the aluminum or aluminum alloy mask layer is 0.5~1μm.

7. The method for preparing the flexible PI vapor deposition mask according to claim 1, characterized in that, In step S3, the spin coating speed is 1500~3000 r / min, and the thickness of the photoresist layer is 1.5~3 μm; And / or: The etching process used to etch the aluminum or aluminum alloy mask layer is either dry etching or wet etching; And / or: The etching process for etching the PI film is reactive ion etching. The reactive ion etching process is as follows: the etching gas is a mixture of O2 and CF4 in a volume ratio of (800~1200):(10~20), the etching power is 800~1000W, the etching pressure is 0.5~2 torr, the etching temperature is 40~60℃, and the etching time is 8~12min.

8. The method for preparing the flexible PI vapor deposition mask according to claim 1, characterized in that, In step S4, the etching solution is an aluminum metal etching solution, which is a mixture of phosphoric acid, nitric acid, acetic acid and water in a volume ratio of (7.8~8.2):(0.8~1.2):(0.8~1.2):(1.8~2.2), wherein: the concentration of phosphoric acid is 82~85wt%, the concentration of nitric acid is 68~72wt%, and the acetic acid is pure acetic acid; And / or: The corrosion temperature is 35~45℃, and the corrosion time is 30~120min.

9. A flexible PI vapor deposition mask, characterized in that, It is prepared by any of the preparation methods described in claims 1 to 9.

10. An application of a flexible PI vapor deposition mask, characterized in that, The flexible PI evaporation mask of claim 9 is used to deposit a metal layer on an irregularly shaped substrate.

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