Method for manufacturing high aspect ratio MEMS free-standing gas permeable membrane and device

Abstract

The application relates to a preparation method of a high-depth-width-ratio MEMS suspended air permeable membrane and a device. The preparation method comprises the following steps: providing a support substrate and a plurality of air-permeable hole positioning columns prepared on the support substrate; preparing an air permeable membrane layer covering the front surface of the support substrate on the support substrate, wherein the air-permeable hole positioning columns are embedded in the air permeable membrane layer, and the upper end of the air-permeable hole positioning columns is exposed from the air permeable membrane layer; performing back cavity etching process on the back surface of the support substrate to form a required back cavity, wherein the formed back cavity is in direct correspondence with the air-permeable hole positioning columns in the air permeable membrane layer; and removing the air-permeable hole positioning columns in the air permeable membrane layer to form air permeable holes penetrating through the air permeable membrane layer in the air permeable membrane layer, wherein the air permeable holes are communicated with the back cavity. The application can effectively prepare the suspended air permeable membrane with high-depth-width-ratio air permeable holes, reduces the complexity of the process, and improves the performance of the suspended air permeable membrane.

Description

Technical Field

[0001] This invention relates to a fabrication method and device, and more particularly to a fabrication method and device for a high aspect ratio MEMS suspended permeable membrane. Background Technology

[0002] Micro-mechanical systems (MEMS) fabrication is a means of manufacturing microstructures, microsensors, and systems. Among them, suspended thin-film structures are one of the most commonly used structures for MEMS devices.

[0003] Currently, MEMS devices with suspended structures are generally fabricated using thermal oxidation or deposition processes. The specific process includes: forming a sacrificial layer on the substrate; forming a suspended structure on the sacrificial layer; and finally removing the sacrificial layer by selective etching.

[0004] In the above process, if the sacrificial layer is too thin, it cannot meet the requirement of high aspect ratio; if the sacrificial layer is too thick, the internal stress of the fabrication process will cause the suspended structure to warp or be compressed, thereby affecting the device performance and making it difficult to meet the actual application requirements. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the existing technology and provide a method and device for preparing a high aspect ratio MEMS suspended breathable membrane, which can effectively prepare a suspended breathable membrane with high aspect ratio pores, reduce the complexity of the process, and improve the performance of the suspended breathable membrane.

[0006] According to the technical solution provided by the present invention, a method for preparing a high aspect ratio MEMS suspended breathable membrane includes: A support substrate and a plurality of vented positioning posts prepared on the support substrate are provided; A breathable membrane layer covering the front side of the support substrate is prepared on the above-mentioned support substrate, wherein the vent positioning post is embedded in the breathable membrane layer, and the upper end of the vent positioning post is exposed from the breathable membrane layer. A back cavity etching process is performed on the back side of the above-mentioned support substrate to form the required back cavity, wherein the formed back cavity corresponds to the vent positioning post in the vent membrane layer. Remove the vent positioning posts in the above-mentioned breathable membrane layer to form a vent that penetrates the breathable membrane layer, and the vent is connected to the back cavity.

[0007] When fabricating a breathable film layer on the front side of the supporting substrate, the following steps are included: A breathable membrane base material is provided for preparing a breathable membrane layer, the breathable membrane base material being formed by mixing an initiator, a leveling agent, an antifoaming agent, and an organic film-forming resin; The breathable membrane base material is placed on the front side of the support substrate to form a breathable membrane layer after drying and curing. The above-mentioned breathable membrane layer is thinned so that the upper end of the vent positioning post embedded in the breathable membrane layer is exposed.

[0008] Organic film-forming resins include one of acrylic resins, epoxy resins, polyurethanes, PP, PET, PE, cellulose acetate, polyethersulfone, or polyvinylidene fluoride; Initiators include one of maleic anhydride, benzidine, or isophorone diamine; Leveling agents include either thermosetting leveling agents or UV-curing leveling agents; Defoamers include one of the following: fluorocarbon defoamers, acrylic resin defoamers, or epoxy resin defoamers.

[0009] When the organic film-forming resin used in the preparation of the breathable membrane base material is a non-epoxy resin, the amount of initiator is 1% to 3% of the weight of the organic film-forming resin, the amount of leveling agent is 0.1% to 1% of the weight of the organic film-forming resin, and the amount of defoamer is 0.1% to 0.6% of the weight of the organic film-forming resin. When epoxy resin is used as the organic film-forming resin and maleic anhydride is used as the initiator, the relationship between the weight of the initiator and the epoxy resin satisfies: W1=AE*E1*K, where W1 is the content of initiator required per 100g of epoxy resin, AE is the molar mass of maleic anhydride, E1 is the epoxy content of the epoxy resin, and K is the mass of maleic anhydride required per mole of epoxy group in the epoxy resin. When epoxy resin is used as the organic film-forming resin and benzidine or isophorone diamine is used as the initiator, the relationship between the weight of the initiator and the epoxy resin satisfies: W2 = (M / Hn) * E2, where M is the molecular weight of the initiator, Hn is the number of active hydrogen atoms on the amine group in the initiator molecule, and E2 is the epoxy content of the epoxy resin.

[0010] For the vent positioning posts fabricated on the support substrate, including: A pre-filled pre-compartment is prepared on the front side of a support substrate, wherein the pre-filled pre-compartment includes a plurality of pre-filled pre-compartment grooves with a high aspect ratio, the pre-filled pre-compartment grooves penetrating the pre-filled pre-compartment; Ventilation hole positioning posts are prepared in the aforementioned pre-filled groove, and after the ventilation hole positioning posts are prepared, the pre-filled material on the support substrate is removed to form a plurality of ventilation hole positioning posts on the front side of the support substrate.

[0011] For the filling pre-ligand prepared on the front side of the support substrate, the material of the filling pre-ligand includes positive photoresist or negative photoresist SU-8.

[0012] The vent positioning posts are filled into the pre-filled tank by electroplating, wherein, The material of the vent positioning post includes Ni or copper.

[0013] The vent positioning post was removed using a wet etching method. When the material of the vent positioning post is silicon, the etching solution used in the wet etching includes KOH solution, NaOH solution, or a mixture of HF solution and HNO3 solution; When the material of the vent positioning post is metal, the corrosion liquid used in the wet corrosion is a metal corrosion liquid that is compatible with the material of the vent positioning post.

[0014] The supporting substrate includes a silicon substrate, an SOI substrate, or a photosensitive glass substrate; The depth-to-width ratio of the pre-mixed filling groove is greater than 10.

[0015] A high aspect ratio MEMS suspended permeable membrane device includes a MEMS suspended permeable membrane, wherein, The MEMS suspended breathable membrane was prepared using the method described above.

[0016] Advantages of this invention: A breathable membrane layer is prepared on a support substrate using a breathable membrane substrate. After the support substrate is etched to form a back cavity, the vent positioning posts are removed, and vent holes are formed in the breathable membrane layer, thus realizing the preparation of a suspended breathable membrane. Based on the characteristics of the breathable membrane substrate, the film-forming material of the suspended breathable membrane is unconstrained. The breathable membrane layer can be patterned according to requirements, and the depth and diameter of the vent holes are controllable. It has excellent performance, low cost, and can be mass-produced, thereby expanding the application fields of MEMS suspended breathable membranes. Attached Figure Description

[0017] Figure 1 This is a flowchart of one embodiment of the preparation method of the present invention.

[0018] Figures 2-9 This is a cross-sectional view of the process steps in Embodiment 1 of the present invention, wherein, Figure 2 This is a cross-sectional view of the seed layer prepared on the basic substrate according to the present invention.

[0019] Figure 3 This is a cross-sectional view of the first photoresist layer prepared on the seed layer according to the present invention.

[0020] Figure 4 This is a cross-sectional view of the patterned first photoresist layer according to the present invention.

[0021] Figure 5 This is a cross-sectional view of the first vent positioning post prepared according to the present invention.

[0022] Figure 6 This is a cross-sectional view of the first breathable membrane layer prepared according to the present invention.

[0023] Figure 7This is a cross-sectional view of the first breathable membrane layer after thinning according to the present invention.

[0024] Figure 8 This is a cross-sectional view of the back side of the basic substrate after cavity etching according to the present invention.

[0025] Figure 9 This is a cross-sectional view of the present invention after the first vent positioning post has been removed.

[0026] Figures 10-16 This is a cross-sectional view of the process steps in Embodiment 2 of the present invention, wherein, Figure 10 This is a cross-sectional view of the support substrate of the present invention when an SOI substrate is used.

[0027] Figure 11 This is a cross-sectional view of the patterned second photoresist layer coated on an SOI substrate according to the present invention.

[0028] Figure 12 This is a cross-sectional view of the SOI substrate being etched using a patterned second photoresist layer according to the present invention.

[0029] Figure 13 This is a cross-sectional view of the second breathable membrane layer prepared according to the present invention.

[0030] Figure 14 This is a cross-sectional view of the second breathable membrane layer after thinning according to the present invention.

[0031] Figure 15 This is a cross-sectional view of the back side of the SOI substrate after etching according to the present invention.

[0032] Figure 16 This is a cross-sectional view of the present invention after the second vent positioning post has been removed.

[0033] Explanation of reference numerals in the attached figures: 1-basic substrate, 2-seed layer, 3-first photoresist layer, 4-pre-filled trench in the first photoresist layer, 5-first vent positioning post, 6-first vent film layer, 7-basic substrate trench, 8-seed layer trench, 9-first vent film hole, 10-SOI substrate, 11-second photoresist layer, 12-second photoresist layer window, 13-back substrate, 14-intermediate insulating layer, 15-top silicon, 16-second vent positioning post, 17-second vent film, 18-back substrate trench, 19-intermediate insulating layer trench, and 20-second vent film hole. Detailed Implementation

[0034] The present invention will be further described below with reference to specific accompanying drawings and embodiments.

[0035] In order to effectively prepare a suspended permeable membrane with high aspect ratio pores, in one embodiment of the present invention, the preparation method for a high aspect ratio MEMS suspended permeable membrane includes: A support substrate and a plurality of vented positioning posts prepared on the support substrate are provided; A breathable membrane layer covering the front side of the support substrate is prepared on the above-mentioned support substrate, wherein the vent positioning post is embedded in the breathable membrane layer, and the upper end of the vent positioning post is exposed from the breathable membrane layer. A back cavity etching process is performed on the back side of the above-mentioned support substrate to form the required back cavity, wherein the formed back cavity corresponds to the vent positioning post in the vent membrane layer. Remove the vent positioning posts in the above-mentioned breathable membrane layer to form a vent that penetrates the breathable membrane layer, and the vent is connected to the back cavity.

[0036] Specifically, the support substrate can take the form commonly used in the present, such as a silicon substrate, an SOI (Silicon-On-Insulator) substrate, or a photosensitive glass substrate; generally, the support substrate has a front side and a back side corresponding to the front side, and the vent positioning post is generally located on the front side of the support substrate or corresponds to the front side of the support substrate.

[0037] Depending on the type of support substrate, the fabrication process and method for the vent positioning posts on the support substrate vary. For example, when the support substrate is a silicon substrate or a photosensitive glass substrate, the fabrication process for the vent positioning posts on the support substrate includes: A pre-filled pre-compartment is prepared on the front side of a support substrate, wherein the pre-filled pre-compartment includes a plurality of pre-filled pre-compartment grooves with a high aspect ratio, the pre-filled pre-compartment grooves penetrating the pre-filled pre-compartment; Ventilation hole positioning posts are prepared in the aforementioned pre-filled groove, and after the ventilation hole positioning posts are prepared, the pre-filled material on the support substrate is removed to form a plurality of ventilation hole positioning posts on the front side of the support substrate.

[0038] In specific implementation, the filling pre-ligand prepared on the front side of the support substrate is made of a material including positive photoresist or negative photoresist SU-8. When using positive or negative photoresist SU-8, it is necessary to first coat the positive or negative photoresist SU-8 onto the front side of the support substrate, and then pattern the coated photoresist layer. The filling pre-ligand groove can be formed by using the window that penetrates the patterned photoresist layer. For the specific process of preparing the filling pre-ligand and the filling pre-ligand groove, please refer to [reference needed]. Figure 3 and Figure 4 The process.

[0039] When the pre-filling material is photoresist, in one embodiment of the present invention, the vent positioning post is filled into the pre-filling groove by electroplating, wherein... The material of the vent positioning post includes Ni or copper.

[0040] In practice, the thickness of the pre-filled compound and the patterning process conditions for the pre-filled compound are selected to obtain a depth-to-width ratio of the pre-filled groove greater than 10. The depth-to-width ratio of the pre-filled groove can be obtained by selecting the process according to actual needs, specifically to meet the actual application requirements. After the pre-filled groove is prepared, an vent positioning post is formed in the pre-filled groove using an electroplating process. The height of the vent positioning post is generally less than the depth of the pre-filled groove. At this time, the vent positioning post is a metal post.

[0041] As explained above, since the pre-filled groove passes through the pre-filled material, after the vent positioning post is electroplated within the pre-filled groove, its lower end corresponds directly to or rests on the support substrate. Generally, the material of the vent positioning post can be Ni or copper. The material for the vent positioning post should generally be one that does not interfere with the removal of the pre-filled material and the back cavity etching process on the support substrate; the specific material type can be selected as needed.

[0042] When the support substrate is an SOI substrate, the specific method for fabricating the vent positioning posts will be described in detail below with reference to Example 2.

[0043] After the vent positioning post is prepared, a vent membrane layer for forming a vent membrane needs to be prepared on the front side of the support substrate. Specifically, the prepared vent membrane layer covers the front side of the support substrate and also covers the vent positioning post. However, in order to form a vent, the upper end of the vent positioning post needs to be exposed from inside the vent membrane.

[0044] In one embodiment of the present invention, the preparation of a breathable film layer on the front side of a supporting substrate includes: A breathable membrane base material is provided for preparing a breathable membrane layer, the breathable membrane base material being formed by mixing an initiator, a leveling agent, an antifoaming agent, and an organic film-forming resin; The breathable membrane base material is placed on the front side of the support substrate to form a breathable membrane layer after drying and curing. The above-mentioned breathable membrane layer is thinned so that the upper end of the vent positioning post embedded in the breathable membrane layer is exposed.

[0045] Specifically, in the breathable membrane base material, the initiator promotes the curing of the organic film-forming resin, and the leveling agent is used to obtain a relatively smooth and even breathable membrane layer. During the mixing and preparation process, many air bubbles are introduced. The defoamer is used to shorten the defoaming time, improve the film quality, and reduce the possibility of performance being affected by air bubbles.

[0046] In preparation, an organic film-forming resin is typically added to a solvent first, followed by leveling agents and defoamers in a specific ratio. The mixture is then stirred evenly using a high-speed disperser, and finally, an initiator is added and stirred until homogeneous. The solvent can be a volatile, low-boiling-point solvent, such as ethanol or acetone.

[0047] In one embodiment of the present invention, the organic film-forming resin includes one of acrylic resin, epoxy resin, polyurethane, PP, PET, PE, cellulose acetate, polyethersulfone, or polyvinylidene fluoride. Initiators include one of maleic anhydride, benzidine, or isophorone diamine; Leveling agents include either thermosetting leveling agents or UV-curing leveling agents; Defoamers include one of the following: fluorocarbon defoamers, acrylic resin defoamers, or epoxy resin defoamers.

[0048] In practice, the initiator, leveling agent, defoamer and organic film-forming resin are uniformly mixed and prepared. The uniformly mixed liquid is then applied to the front side of the support substrate by spraying or spin coating, and a breathable film layer is formed by drying and curing.

[0049] In the above-mentioned organic film-forming resins, when a non-epoxy resin is used as the organic film-forming resin to form the breathable membrane base material, the amount of initiator is 1% to 3% of the weight of the organic film-forming resin, the amount of leveling agent is 0.1% to 1% of the weight of the organic film-forming resin, and the amount of defoamer is 0.1% to 0.6% of the weight of the organic film-forming resin. When epoxy resin is used as the organic film-forming resin and maleic anhydride is used as the initiator, the relationship between the weight of the initiator and the epoxy resin satisfies: W1=AE*E1*K, where W1 is the content of initiator required per 100g of epoxy resin, AE is the molar mass of maleic anhydride, E1 is the epoxy content of the epoxy resin, and K is the mass of maleic anhydride required per mole of epoxy group in the epoxy resin. When epoxy resin is used as the organic film-forming resin and benzidine or isophorone diamine is used as the initiator, the relationship between the weight of the initiator and the epoxy resin satisfies: W2 = (M / Hn) * E2, where M is the molecular weight of the initiator, Hn is the number of active hydrogen atoms on the amine group in the initiator molecule, and E2 is the epoxy content of the epoxy resin.

[0050] When epoxy resin is used as the organic film-forming resin, the amount of leveling agent and defoamer can be the same as when non-epoxy resin is used as the organic film-forming resin. Please refer to the above instructions for details, which will not be repeated here.

[0051] In the leveling agent, the thermosetting agent and UV curing agent can be the commonly used curing agent forms, and can be selected according to the needs. Therefore, as can be seen from the above description, based on the characteristics of the breathable membrane base material, the suspended breathable film forming material is unconstrained. The unconstrained nature specifically means that the breathable membrane base material can be cured by light or heat, and has strong compatibility with materials. It is not unique, as long as it does not react with the reagents used in the subsequent wet etching.

[0052] To effectively enclose the vent positioning posts, the thickness of the vent membrane layer is generally greater than the height of the posts. Therefore, the vent membrane layer needs to be thinned to expose the upper end of the vent positioning posts. Specifically, the upper end of the vent positioning posts refers to the end furthest from the supporting substrate. Commonly used methods, such as grinding, can be used to thin the vent membrane layer, and the appropriate method can be selected based on the specific needs.

[0053] To create the suspended form, a cavity etching process is required on the back side of the supporting substrate. After the cavity etching process, a cavity is formed, which generally penetrates the substrate, meaning the depth of the cavity is not less than the thickness of the supporting substrate. The process conditions for the cavity etching process can be selected as needed, based on the requirement of being able to perform cavity etching on the supporting substrate.

[0054] In order to form a breathable structure, the vent positioning posts need to be removed. In one embodiment of the present invention, a wet etching method is used to remove the vent positioning posts. When the material of the vent positioning post is silicon, the etching solution used in the wet etching includes KOH solution, NaOH solution, or a mixture of HF solution and HNO3 solution; When the material of the vent positioning post is metal, the corrosion liquid used in the wet corrosion is a metal corrosion liquid that is compatible with the material of the vent positioning post.

[0055] In practical implementation, during wet etching, the etching solution used should be sufficient to remove the vent positioning posts without affecting the vent membrane layer and the supporting substrate. If the vent positioning posts are made of silicon, the etching solution can be a mixture of KOH, NaOH, HF, and HNO3 solutions. If the vent positioning posts are made of metal, a metal etching solution capable of etching the metal vent positioning posts should be used. The concentration of the etching solution can be selected as needed or according to industry standards, specifically to remove the vent positioning posts. When mixing HF and HNO3 solutions, the volume ratio of HNO3 to HF can be selected as 2:6, the concentration of HNO3 can be selected as 68%, and the concentration of HF solution can be selected as 49%. During the process, water or acetic acid can be added to dilute the mixture and slow down the etching rate.

[0056] After removing the vent positioning posts, as described above, several vent holes can be formed within the vent membrane layer. These vent holes penetrate the vent membrane layer. Since the back cavity corresponds to the vent positioning posts, the vent holes can then correspond to and communicate with the back cavity. The entire vent membrane is supported on a supporting substrate. As can be seen from the fabrication process of the vent positioning posts, the formed vent holes also have a high aspect ratio.

[0057] In summary, high aspect ratio MEMS suspended permeable membrane devices can be obtained, including MEMS suspended permeable membranes, wherein, The MEMS suspended breathable membrane was prepared using the method described above.

[0058] Specifically, the suspended permeable membrane device includes at least a MEMS suspended permeable membrane, which can be prepared by the above-described preparation method; in addition, the preparation method of the present invention will be specifically described below through Examples 1 and 2.

[0059] Example 1 like Figures 2-9 The diagram shows the process flow for fabricating a suspended permeable membrane using a non-SOI substrate 10. The specific process includes: Step 1: Provide a basic substrate 1 required for device fabrication, and grow a seed layer 2 of 30nm to 50nm by evaporation or sputtering. Specifically, the basic substrate 1 can be a silicon substrate, the seed layer 2 can be Au, and the process conditions and procedures for preparing the seed layer 2 can be consistent with the existing ones, with the specific requirements being that the seed layer 2 can be prepared. Figure 2 The diagram shows an embodiment where the seed layer 2 covers the front side of the base substrate 1. The seed layer 2 facilitates conductivity during subsequent electroplating processes.

[0060] Step 2: Take an appropriate amount of photoresist liquid and drop it onto the center of the base substrate 1 with seed layer 2. Then, rotate the spin coater at a low speed of 500r / s to 800r / s for 5s to 10s to spread the photoresist liquid on the substrate. Then, accelerate to 3000r / s to 4000r / s and rotate for 20s to 40s to coat the base substrate 1 with a uniform thickness. Then, place the base substrate 1 coated with photoresist on a hot plate at 110℃ to 125℃ for baking for 3min to 5min to form the first photoresist layer 3. Figure 3 The illustration shows an embodiment in which the first photoresist layer 3 covers the seed layer 2. Of course, in specific implementation, other forms can also be used to prepare the first photoresist layer 3 on the seed layer 2. The type of photoresist used for the first photoresist layer 3 is as described above, which can be positive photoresist or negative photoresist SU-8.

[0061] Step 3: Pattern the first photoresist layer 3 prepared above to obtain a plurality of pre-filled grooves 4 in the first photoresist layer 3 that penetrate the first photoresist layer 3. Patterning the first photoresist layer 3 includes common steps such as exposure and development, ultimately resulting in a pre-filled groove 4 within the first photoresist layer, such as... Figure 4 As shown, at this time, the first photoresist layer 3 is used to form a pre-filled pre-fit, and the patterned window forms a pre-fit groove, that is, a photoresist layer is filled with a pre-fit groove 4.

[0062] Step 4: Place the first photoresist layer 3 on a hot plate at 110-130°C for baking for 5-15 minutes, and then electroplate with Ni metal. Specifically, after electroplating with Ni metal, a first vent positioning post 5 is obtained, which is located within the first photoresist layer and filled with a pre-fitted groove 4. That is, the first vent positioning post 5 is the aforementioned vent positioning post. Figure 5 As shown.

[0063] Step 5: Remove the first photoresist layer 3 to obtain the first vent positioning post 5 distributed on the seed layer 2; Specifically, acetone or a special photoresist remover can be used to remove the first photoresist layer 3. After the first photoresist layer 3 is removed, only the first vent positioning post 5 is retained on the seed layer 2.

[0064] Step 6: Apply a heat-curing breathable film base material to the front side of the above basic substrate 1 using spray adhesive. The heat curing temperature is 160℃~200℃ and the baking time is 20min~30min to achieve the required drying and curing. Specifically, the thermosetting breathable membrane base material includes epoxy resin and maleic anhydride. That is, the organic film-forming resin is epoxy resin, and the initiator is maleic anhydride. The amount of maleic anhydride used needs to be based on W1=AE*E1*K, where W1 refers to the amount of maleic anhydride required per 100g of epoxy resin, AE is the molar mass of maleic anhydride, E1 is the epoxy content of epoxy resin, and K is the amount of maleic anhydride required per mole of epoxy group in epoxy resin, which is generally taken as 0.85.

[0065] The leveling agent is an ether-modified siloxane, wherein the amount of ether-modified siloxane is 0.1% to 0.3% of the epoxy resin weight, the amount of epoxy resin defoamer is 0.2% to 0.4% of the epoxy resin weight, and the amount of acetone is 9:1 or 10:1 in volume ratio of acetone to epoxy resin; here, the solvent is acetone.

[0066] Specifically, the breathable membrane layer can be made of epoxy resin. The epoxy resin can be applied to the front side of the basic substrate 1 by spraying, and then cured by thermosetting. At this time, the breathable membrane layer can be obtained, that is... Figure 6 The first breathable membrane layer 6 in the middle.

[0067] Step 7: Thin the first breathable membrane layer 6 to expose the upper end of the electroplated first breathable hole positioning post 5; Specifically, commonly used thinning methods, such as grinding, can be employed. The result after grinding is as follows: Figure 7 As shown.

[0068] Step 8: Perform a back cavity etching process on the back side of the above-mentioned basic substrate 1 to obtain a basic substrate trench 7 that penetrates the basic substrate 1. Specifically, the basic substrate trench 7 penetrates the basic substrate 1. During back cavity etching, NaOH wet etching can be used. The basic substrate trench 7 corresponds to the area of ​​the first vent positioning post 5 within the first vent film layer 6, such as... Figure 8 As shown.

[0069] Step 9: Remove the first vent positioning post 5 and perform wet etching on the seed layer 2; Specifically, the first vent positioning post 5 can be removed before wet etching of the seed layer 2; or, the seed layer 2 can be wet etched first before removing the first vent positioning post 5. The specific order can be selected as needed. When removing the first vent positioning post 5, a mixture of HF solution and HNO3 solution can be used to etch the first vent positioning post 5; potassium iodide solution can be used to etch the seed layer 2.

[0070] The following is a detailed explanation of the process steps, taking the wet etching of seed layer 2 followed by the removal of the first vent positioning post 5 as an example: After obtaining the basic substrate trench 7, the seed layer 2 needs to be etched to obtain the seed layer trench 8 that runs through the seed layer 2. The seed layer trench 8 corresponds to and is connected to the basic substrate trench 7, that is, the basic substrate trench 7 and the seed layer trench 8 are used to form a back cavity.

[0071] After obtaining the seed layer groove 8, the aforementioned first vent positioning post 5 needs to be removed. At this time, a first vent membrane hole 9 communicating with the back cavity can be formed in the first vent membrane layer 6, such as... Figure 9 As shown.

[0072] Example 2 like Figures 10-16 As shown, when SOI is used as the supporting substrate, the specific fabrication method includes: Step 100: Provide an SOI substrate 10 required for device fabrication, and coat a layer of photoresist on the SOI substrate 10 to form a second photoresist layer 11; like Figure 10 As shown, the SOI substrate 10 generally includes a back substrate 13, an intermediate insulating layer 14 disposed on the back substrate 13, and a top silicon layer 15 disposed on the intermediate insulating layer 14. The specific details of the SOI substrate 10 are consistent with those of the prior art.

[0073] The second photoresist layer 11 is generally prepared on the top silicon layer 15. The process of coating the second photoresist layer 11 on the top silicon layer 15 can be as follows: take an appropriate amount of photoresist liquid and drop it onto the center of the top silicon layer 15, then rotate the spin coater at a low speed of 500r / s to 800r / s for 5s to 10s to spread the photoresist liquid on the top silicon layer 15; then accelerate to 3000r / s to 4000r / s and rotate for 20s to 40s to coat the photoresist onto the top silicon layer 15 with a uniform thickness; then place the top silicon layer 15 coated with photoresist on a hot plate at 110℃ to 125℃ for baking for 3min to 5min to form the second photoresist layer 11, which has a thickness of 5 to 15μm.

[0074] The second photoresist layer 11 is patterned using a common patterning process to obtain the second photoresist layer window 12. The second photoresist layer window 12 exposes the corresponding surface of the top silicon layer 15, such as... Figure 11 As shown.

[0075] Step 110: The top silicon 15 is etched using the patterned second photoresist layer 11 to obtain a plurality of second vent hole positioning posts 16. That is, the material of the second vent hole positioning posts 16 is silicon. Of course, after etching to form the second vent hole positioning posts 16, the second photoresist layer 11 needs to be removed using techniques from this technical field, such as... Figure 12 As shown.

[0076] Step 120: Prepare a second permeable film layer 17 on the SOI substrate 10. The second permeable film layer 17 can cover the second vent positioning post 16, such as... Figure 13 As shown.

[0077] The obtained device groove is repeatedly filled with thermosetting breathable membrane material under vacuum conditions (vacuum value 0.05Mpa~0.2Mpa), wherein the thermosetting temperature is 160℃~200℃ and the baking time is 20min~30min. Figure 15 As shown.

[0078] In one embodiment of the present invention, the breathable membrane base material includes epoxy resin and benzidine, that is, the organic film-forming resin is epoxy resin, and the initiator is benzidine. Specifically, the amount of benzidine used needs to be based on W2=(M / Hn)*E2, where W2 refers to the amount of benzidine required per 100g of epoxy resin, M is the molecular weight of benzidine, E2 is the epoxy content of epoxy resin, and Hn is the number of active hydrogen atoms on the amine group in the benzidine molecule; the leveling agent is ether-modified siloxane, and the amount of ether-modified siloxane is 0.4% to 1% of the weight of epoxy resin; the amount of epoxy resin defoamer is 0.3% to 0.6% of the weight of epoxy resin.

[0079] Step 130: Thin the second breathable membrane layer 17 so that the upper end of the second vent positioning post 16 is exposed, such as... Figure 14 As shown.

[0080] Step 140: Perform back cavity etching on the back substrate 13 to obtain a back substrate trench 18 that penetrates the back substrate 13. Specifically, the process for forming the back substrate trench 18 can be referred to the above description, with the specific method depending on whether the back substrate trench 18 can be formed. Figure 15 As shown.

[0081] Step 150: Using a process commonly used in this technical field, the second vent positioning post 16 is removed, and the intermediate insulating layer 14 corresponding to the back substrate groove 18 is etched. At this point, an intermediate insulating layer groove 19 corresponding to and connected to the back substrate groove 18 is obtained. After the second vent positioning post 16 is removed, a plurality of second vent membrane holes 20 are formed within the second vent membrane layer 17, such as... Figure 16 As shown. The depth-to-space ratio of the second vent membrane pore 20 can be adjusted according to the second vent positioning post 16, as described above.

[0082] In practice, the suspended breathable membrane can also be prepared using other MEMS processes. Please refer to the above description for details, and the specific process should be based on the ability to prepare the required MEMS suspended breathable membrane.

Claims

1. A method for preparing a high aspect ratio MEMS suspended permeable membrane, characterized in that, The preparation method includes: A support substrate and a plurality of vented positioning posts prepared on the support substrate are provided; A breathable membrane layer covering the front side of the support substrate is prepared on the above-mentioned support substrate, wherein the vent positioning post is embedded in the breathable membrane layer, and the upper end of the vent positioning post is exposed from the breathable membrane layer. A back cavity etching process is performed on the back side of the above-mentioned support substrate to form the required back cavity, wherein the formed back cavity corresponds to the vent positioning post in the vent membrane layer. Remove the vent positioning posts in the above-mentioned breathable membrane layer to form a vent that penetrates the breathable membrane layer, and the vent is connected to the back cavity.

2. The method for preparing a high aspect ratio MEMS suspended breathable membrane according to claim 1, characterized in that, When fabricating a breathable film layer on the front side of the supporting substrate, the following steps are included: A breathable membrane base material is provided for preparing a breathable membrane layer, the breathable membrane base material being formed by mixing an initiator, a leveling agent, an antifoaming agent, and an organic film-forming resin; The breathable membrane base material is placed on the front side of the support substrate to form a breathable membrane layer after drying and curing. The above-mentioned breathable membrane layer is thinned so that the upper end of the vent positioning post embedded in the breathable membrane layer is exposed.

3. The method for preparing a high aspect ratio MEMS suspended breathable membrane according to claim 2, characterized in that, Organic film-forming resins include one of acrylic resins, epoxy resins, polyurethanes, PP, PET, PE, cellulose acetate, polyethersulfone, or polyvinylidene fluoride; Initiators include one of maleic anhydride, benzidine, or isophorone diamine; Leveling agents include either thermosetting leveling agents or UV-curing leveling agents; Defoamers include one of the following: fluorocarbon defoamers, acrylic resin defoamers, or epoxy resin defoamers.

4. The method for preparing a high aspect ratio MEMS suspended breathable membrane according to claim 3, characterized in that, When the organic film-forming resin used in the preparation of the breathable membrane base material is a non-epoxy resin, the amount of initiator is 1% to 3% of the weight of the organic film-forming resin, the amount of leveling agent is 0.1% to 1% of the weight of the organic film-forming resin, and the amount of defoamer is 0.1% to 0.6% of the weight of the organic film-forming resin.

5. The method for preparing a high aspect ratio MEMS suspended breathable membrane according to any one of claims 1 to 4, characterized in that, For the vent positioning posts fabricated on the support substrate, including: A pre-filled pre-compartment is prepared on the front side of a support substrate, wherein the pre-filled pre-compartment includes a plurality of pre-filled pre-compartment grooves with a high aspect ratio, the pre-filled pre-compartment grooves penetrating the pre-filled pre-compartment; Ventilation hole positioning posts are prepared in the aforementioned pre-filled groove, and after the ventilation hole positioning posts are prepared, the pre-filled material on the support substrate is removed to form a plurality of ventilation hole positioning posts on the front side of the support substrate.

6. The method for preparing a high aspect ratio MEMS suspended breathable membrane according to claim 5, characterized in that, For the filling pre-ligand prepared on the front side of the support substrate, the material of the filling pre-ligand includes positive photoresist or negative photoresist SU-8.

7. The method for preparing a high aspect ratio MEMS suspended breathable membrane according to claim 5, characterized in that, The vent positioning posts are filled into the pre-filled tank by electroplating, wherein, The material of the vent positioning post includes Ni or copper.

8. The method for preparing a high aspect ratio MEMS suspended breathable membrane according to claim 7, characterized in that, The vent positioning post was removed using a wet etching method. When the material of the vent positioning post is silicon, the etching solution used in the wet etching includes KOH solution, NaOH solution, or a mixture of HF solution and HNO3 solution; When the material of the vent positioning post is metal, the corrosion liquid used in the wet corrosion is a metal corrosion liquid that is compatible with the material of the vent positioning post.

9. The method for preparing a high aspect ratio MEMS suspended breathable membrane according to claim 5, characterized in that, The supporting substrate is a silicon substrate; The depth-to-width ratio of the pre-mixed filling groove is greater than 10.

10. A high aspect ratio MEMS suspended permeable membrane device, characterized in that, Including MEMS suspended breathable membranes, among which, The MEMS suspended breathable membrane is prepared by any one of the preparation methods described in claims 1 to 9.

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