Microporous membranes and methods of making microporous membranes using a column template

Abstract

The present invention relates to microporous membranes and methods of making microporous membranes using a post template. A porous membrane is provided comprising: a polymer layer defining a bottom surface of the membrane and a top surface of the membrane; a plurality of pores extending through the polymer layer, each pore having a first region and a second region, the first region having a tapered profile, the tapered profile opening wider at an intersection of the top surface of the membrane, the second region having a substantially vertical profile, the substantially vertical profile intersecting the bottom surface of the membrane, the first region intersecting the second region at an intermediate surface, the intermediate surface facing exposure through an opening created by the first region. A post template for making a porous membrane is also provided.

Description

[0001] This application is a divisional application of the invention patent application filed on March 29, 2022, with application number 202280025746.0 (PCT / EP2022 / 058220) and entitled "Microporous Membrane and Method for Manufacturing Microporous Membrane Using Column Template". Technical Field

[0002] This invention relates to microporous membranes and a method for manufacturing microporous membranes using a column template. Background Technology

[0003] Porous membranes are used in various biofiltration processes. The membrane is made of a thin layer of polymer material in which pores are formed.

[0004] Photolithography has been used to manufacture film materials. U.S. Patent 7,784,619, issued to Jacobsen and assigned to Baxter International, Inc., describes photolithographic methods for manufacturing films. These methods use conventional semiconductor manufacturing techniques to produce films with a desired series of pores. The inventors have discovered that standard techniques used in semiconductor manufacturing cannot provide large surface area films with the desired properties.

[0005] Therefore, the present invention seeks to improve microporous membranes and their manufacturing methods. Summary of the Invention

[0006] In one aspect, the present invention relates to a porous membrane (101) having a polymer layer (102) and a plurality of pores (105). The polymer layer (102) defines a bottom surface (103) and a top surface (104) of the membrane. The plurality of pores (105) extend through the polymer layer (102), each pore (105) having a first region (106) and a second region (108), the first region having a tapered profile (107) that opens wider at its intersection with the top surface (104) of the membrane, the second region having a substantially vertical profile (109) that intersects with the bottom surface (103) of the membrane, the first region (106) intersecting with the second region (108) at an intermediate surface (110) that faces exposure through the opening created by the first region (106). The substantially vertical profile may have an angle Ɵ from the horizontal plane ranging from 80° to 100°, preferably from the horizontal plane ranging from 85° to 95°, and more preferably from the horizontal plane at about 90°.

[0007] In one aspect, the intermediate surface of each aperture has a surface area that varies between apertures to a greater extent than the opening surface area defined by the second region. In another aspect, the effective aperture is defined by a columnar template at the bottom surface of the membrane, thereby allowing greater tolerance in terms of variability in etching through thick regions of the polymer layer. In another aspect, the first region has a conical profile.

[0008] In one aspect, the membrane may include a pore region containing pores and a tear-resistant ring surrounding the pore region. The polymer layer may be divided into a plurality of individual membranes, each membrane having an optional tear-resistant ring around its periphery. The membrane preferably has a thickness in the range of 3 to 50 micrometers. The polymer layer may have a thickness of 0.1 μm. 2 Or a larger surface area. It is generally desirable to maximize the size of the polymer layer in order to increase manufacturing output in terms of the number of films produced per batch.

[0009] The membrane layer may contain at least one material selected from polyimide, polyamide, polycarbonate, polyetherimide, polyetherketone, polyurethane, synthetic polymer, low-density polyethylene (LDPE), high-density polyethylene (HDPE), polypropylene (PP), polyvinyl chloride (PVC), polystyrene (PS), nylon, Teflon (polytetrafluoroethylene), thermoplastic polyurethane (TPU), polyethylene, acrylate polymers, acrylate monomers and / or acrylate elastomers.

[0010] In another aspect, the present invention may relate to a method for manufacturing a porous membrane. The method includes (a) depositing a polymer layer (202) on a pillar template (200), the pillar template (200) including a plurality of pillars (213') defining pores of a membrane material on a glass substrate (211) and optionally a release layer (215); (b) depositing a hard mask layer (216) over the polymer layer (202); and (c) patterning the hard mask layer (216) to define a plurality of openings (205) in the hard mask layer (216), the openings corresponding to each (d) Align each post (213') of the hole; remove the polymer layer (202) until the optional release layer (215) above each post (213') or, in the absence of a release layer (215), the post (213') corresponding to each hole is exposed through the first opening (206) in the polymer layer (202); (e) if an optional release layer is used, remove the release layer (215) at least partially; and (f) remove the porous membrane (201) from the post template (200).

[0011] In one aspect, the method may include, after step (f), depositing a second, optional release layer on the column template, and repeating steps (a)-(f) to form a second porous membrane. The hard mask layer and the release layer may be made of the same material, and both may be at least partially removed during step (e). On the other hand, the porous membrane in step (f) may further include a bottom surface (103) and a top surface (104) of the membrane; and a plurality of pores (105) extending through the polymer layer (102), each pore (105) having a first region (106) and a second region (108), the first region having a tapered profile (107) that opens wider at the intersection with the top surface (104) of the membrane formed in step (e), the second region having a substantially vertical profile (109) that intersects with the bottom surface (103) of the membrane formed in step (f), the first region (106) intersecting with the second region (108) at an intermediate surface (110) that faces exposure through the opening created by the first region (106).

[0012] In one aspect, the invention also relates to a pillar template for fabricating a porous membrane, comprising a substrate (211, 411, 511, 611); and a plurality of pillars (213', 413', 513', 613'), the pillars projecting from the substrate at a first height and having a lateral dimension, the pillars corresponding to the pore regions of the porous membrane and having a substantially vertical profile; wherein the first height is in the range of 0.5 to 5 micrometers, and the lateral dimension is in the range of 1 to 5 micrometers. More preferably, the first height is in the range of 1.5 to 2.5 micrometers, and the lateral dimension is in the range of 1.5 to 3 micrometers. In one aspect, the substantially vertical profile has an angle Ɵ in the range of 80° to 100° from the horizontal plane, more preferably in the range of 85° to 95° from the horizontal plane, and most preferably selected from an angle Ɵ of about 90° from the horizontal plane. The plurality of pillars may have different etch rates over the entire thickness of the pillars.

[0013] In one aspect, the substrate (211, 411) may be a glass substrate, and the plurality of pillars (213', 413') may comprise silicon, and the pillar template may also include an adhesion layer (212, 412) on the glass substrate (211, 411). The pillar template may include regions lacking pillars surrounding the regions having pillars, the regions lacking pillars corresponding to tear-resistant rings in the film to be formed by the pillar template. The pillar template may also include a protective layer (415) on the adhesion layer (412) in the regions of the plurality of pillars and between the plurality of pillars. In this case, the protective layer may comprise silicon.

[0014] On the other hand, the substrate (511) may be a glass substrate, and the plurality of pillars (513') may contain silicon nitride, and the pillar template may also include a protective layer (515) on the glass substrate (511) in the region between the plurality of pillars.

[0015] On the other hand, the substrate (611) may be a glass substrate, and the plurality of pillars (613') are glass protrusions integral with the glass substrate, and the pillar template may also include a protective layer (615) on the glass substrate (611) in the region between the plurality of pillars (613'). In this case, the protective layer may include a silicon dioxide layer coated on the glass substrate (611) in the region between the plurality of pillars (613') and the region between the plurality of pillars, and a silicon layer on the silicon dioxide layer of the protective layer.

[0016] In another aspect, the present invention may relate to a method for manufacturing a pillar template (200), comprising the steps of: (a) depositing an adhesion layer (212) on a substrate (211); (b) depositing a pillar material layer (213) on the substrate (211); (c) depositing and patterning a photoresist (214) to define a plurality of pillars in the pillar material layer (213); and (d) removing the pillar material layer (213) exposed by the patterned photoresist (214) until the adhesion layer (212) is exposed to define the plurality of pillars (213'). In this case, the adhesion layer comprises silicon dioxide. In this case, the method may further include step (e) of depositing a protective layer (415) on the adhesion layer (412) in the region between the plurality of pillars. In this case, the protective layer may comprise silicon.

[0017] In another aspect, the present invention may relate to a method for manufacturing a pillar template (500), comprising the steps of: (a) depositing a pillar material layer (513) on a substrate (511); (b) depositing and patterning a photoresist (514) to define a plurality of pillars in the pillar material layer (513); (c) removing the pillar material layer (513) exposed by the patterned photoresist (514) until the substrate (511) is exposed to define a plurality of pillars (513'), wherein the plurality of pillars have a substantially vertical profile; and (d) depositing a protective layer (515) on the plurality of pillars (513') and the exposed substrate (511).

[0018] In another aspect, the present invention may relate to a method for manufacturing a column template (600), comprising the steps of: (a) depositing a hard mask layer (612) over a glass substrate (611); (b) depositing and patterning a photoresist (613) to define a column pattern in the hard mask (612'); (c) removing the glass substrate (611) exposed through the patterned hard mask (612') to form a plurality of columns (611'), wherein the plurality of columns have a substantially vertical profile; and (d) optionally etching the sidewalls of the glass substrate (611) and the glass columns (611'); and (e) removing the patterned hard mask layer (612'); and (f) depositing a protective layer (615) over the glass substrate (611). Attached Figure Description

[0019] Figure 1A A top-down close-up view of the pores of a porous membrane according to an embodiment of the present invention is shown.

[0020] Figure 1B A close-up side view of the pores of a porous membrane according to an embodiment of the present invention is shown.

[0021] Figure 1C A top view of a porous membrane with a tear-resistant ring according to an embodiment of the present invention is shown.

[0022] Figure 1D A top view of several porous membranes manufactured using a single column template according to an embodiment of the present invention is shown.

[0023] Figures 2A-2F The fabrication of a porous membrane according to one embodiment of the present invention is shown.

[0024] Figure 3 This demonstrates how the relationship between pressure (mT) and power (W) affects the sidewall geometry when forming the column of the column membrane described herein.

[0025] Figures 4A-4E The fabrication of a porous membrane according to one embodiment of the present invention is shown.

[0026] Figures 5A-5E The fabrication of a porous membrane according to one embodiment of the present invention is shown.

[0027] Figures 6A-6F The fabrication of a porous membrane according to one embodiment of the present invention is shown. Detailed Implementation

[0028] This invention relates to the production of porous polymer membranes using a column template combined with photolithography and etching techniques. The formation of porous regions in the polymer membrane is described in U.S. Patent Application No. 16 / 842,402, filed April 7, 2020, entitled “POROUS FLAT DEFORMATION-RESISTANT MEMBRANE,” and U.S. Patent Application No. 16 / 842,448, filed April 7, 2020, respectively, both of which are incorporated herein by reference. These applications describe techniques for manufacturing porous polymer membranes using a technology modified from semiconductor manufacturing techniques.

[0029] One challenge in producing polymer films with small pore sizes (<3.0 micrometers) using these techniques is the lack of uniformity in etching through relatively thick polymer film layers, making it difficult to obtain pores of uniform size. In one aspect of the invention, the total polymer etching time can be reduced by using a column template to shorten the length of polymer that needs to be etched through. In the case of a 10-micrometer polymer layer, the invention can accelerate the etching time by 1.25 times by reducing the etching from 10 micrometers to 8 micrometers. In another aspect, the invention provides a more controllable exit hole geometry by using a reusable column template, which can be manufactured individually and subjected to independent quality control, while isolating the etching of larger aspect ratio through-holes from determining the exit hole geometry of the porous membrane.

[0030] A porous membrane 101 according to an embodiment of the present invention is shown in Figures 1A-1B The image shows a close-up top-down and side view of a cross-section of the porous membrane 101. The porous membrane 101 is preferably made of a polyimide material and is a single membrane layer. According to one aspect of the invention described further below, a column template is used to produce the porous membrane 101. When used in conjunction with photolithography on the polymer layer 102 of the porous membrane 101, the column template described herein allows for the formation of a well-defined and reproducible exit size defined by a second region 108. The effective pore size of the membrane is determined by the exit size 108. As explained further below, the column template provides a method for overcoming the difficulties encountered when etching holes in polymer materials due to the non-uniformity encountered when etching high aspect ratio through-holes in polymer materials. Once produced, the column template can be reused several times after applying a new release layer.

[0031] The polymer layer 102 of membrane 101 has a bottom surface 103 and a top surface 104. A plurality of apertures 105 extend through the polymer layer 102. Each aperture has a first region 106 with a tapered profile 107 that opens wider at the intersection with the top surface 104 of the membrane; and a second region 108 with a substantially vertical profile 109 that intersects with the bottom surface 103 of the membrane. As shown in FIG1, the tapered profile 107 may be a conical profile. The first region 106 intersects with the second region 108 at an intermediate surface 110, which is exposed through the opening created by the first region 106. The intermediate surface 110 provides a buffer that allows for non-uniformity in the etching and formation of the first region between apertures within the same membrane and between separate fabrication runs of different membranes.

[0032] The basic vertical profile of the second region 108 / 208 is defined by the basic vertical profile of each column on the column template 200, such as... Figure 2B and Figure 2F As shown. Preferably, the substantially vertical profile of the second region 108 has a range of 80° to 100° relative to the horizontal plane, more preferably a range of 85° to 95° relative to the horizontal plane, and most preferably about 90°. Figure 1B The angle Ɵ is shown. This angle is complementary to the sidewall of each column in the column formwork, such as... Figure 2B As shown. When flow is directed toward the bottom surface 103 of the membrane during operation, it is desirable that the opening forming the second region 108 be minimized at the edge intersecting the bottom surface 103. In other words, the angle Ɵ is greater than 90°, making the opening wider as fluid flows into the membrane. This can prevent or reduce membrane blockage by preventing particles and / or materials that may clog the pores from entering the pores. In some cases, an angle Ɵ greater than 90° can make separation of the membrane from the column template difficult due to the formation of a dovetail-like structure between the membrane and the columns of the column template, which can be used to hold the membrane in place. In some cases, the difficulty of removing the membrane from the column template can be alleviated by using a release layer, which, once removed, provides a gap for separating the membrane opening 108 from the column. In other cases, when the size and material properties allow the membrane to be removed from the column template, a release layer with the desired angle may not be necessary.

[0033] The column template can be made of, for example, glass. Other suitable materials include silicon or metal. The porous membrane 101 is made of a polymer layer 102. In a preferred aspect of the invention, the membrane layer 102 and the column template have similar coefficients of thermal expansion. An ideal material is polyimide. Many grades of polyimides with different CTE values ​​exist. In one aspect, a polyimide having a CTE similar to that of glass is used. The polyimide can be applied to a substrate and cured on the substrate, wherein the CTE of the cured polyimide substrate matches the CTE of the glass. In one embodiment, the polyimide has a CTE of 3 ppm / °C at 50°C to 200°C at a thickness of 20 micrometers, and the glass has a CTE of 3.2 ppm / °C at 50°C to 200°C. As mentioned above, the CTEs of the polymer and the substrate layer should be within ±25% of each other, more preferably within ±15% of each other, and most preferably within ±10%. For example, as mentioned above, the CTE of the glass is about 7% higher than that of the polyimide layer.

[0034] Suitable materials for membrane 102 may include polyimide, polyamide, polycarbonate, polyetherimide, polyetherketone, polyurethane, synthetic polymers, low-density polyethylene (LDPE), high-density polyethylene (HDPE), polypropylene (PP), polyvinyl chloride (PVC), polystyrene (PS), nylon, Teflon (polytetrafluoroethylene), thermoplastic polyurethane (TPU), polyethylene, acrylate polymers, acrylate monomers, or acrylate elastomers. Membrane 102 can be applied to the column template using spin coating, spraying, meniscus coating, slot coating, dip coating, extrusion coating, or lamination (adhesive to substrate). Membrane 102 can be cured using thermosetting, UV curing, or a combination of both.

[0035] Depending on the geometry of the column template, the pores can be uniformly distributed across the entire area of ​​the membrane. Alternatively, the columns can be arranged to provide a pore gradient on the membrane surface. The porous membrane can have a thickness ranging from 3 to 50 micrometers, preferably from 5 to 15 micrometers, and most preferably about 10 micrometers. This invention can be used to provide large-area porous membranes, including those with a surface area exceeding 0.1 m². 2 Those. As further described herein, much larger substrates and film layers can be fabricated as needed. A pillar template can comprise several individual films cut from a single material layer, such as Figure 1D As shown.

[0036] Figure 1CAn exemplary porous membrane on a column template 110 is shown, wherein circular pore regions 112 are surrounded by tear-resistant rings 113. The concept of a tear-resistant ring is disclosed in U.S. Patent Application No. 17 / 115,054, filed December 7, 2020, entitled “MEMBRANE TEAR PREVENTION RING,” the disclosure of which is incorporated herein by reference. Both the pore regions 112 and the tear-resistant rings 113 are made of a polymer layer 102. The tear-resistant rings 113 are pore-free regions within the polymer layer that provide strength to the membrane and prevent tearing during delamination from the column template 110 and during use. Circular patterns are etched in the porous membrane 102 to separate each individual membrane filter from the polymer layer exposed beneath the column template. As will be understood from the disclosure below, the column template may have circular column patterns surrounding the columns corresponding to the pore regions 112, the circular column patterns corresponding to the cut-out circles surrounding the membrane, such that the polymer etching used to create the first region 106 also separates adjacent membranes from each other. Figure 1D Several membranes formed on a single column template are shown.

[0037] Porous membrane 201 is manufactured from column template 200. In one embodiment, the present invention relates to a method such as Figure 2C The pillar template 200 shown manufactures a porous membrane 201. The pillar template includes a glass substrate 211 having an adhesion layer 212 covering a layer of silicon dioxide (e.g., 2500 angstroms) deposited on the glass substrate 211, and pillars 213' of amorphous silicon (e.g., 2 micrometers thick). Prior to use or reuse, the pillar template 200 may be coated with an optional release layer 215, which may be, for example, a 1400 angstrom layer of deposited indium tin oxide (ITO). The pillar template 200 includes pillars patterned onto the glass substrate, which define outlet orifices 208 of the porous membrane 201. Therefore, the pillar template includes a distribution of pillars 213', which may have, for example, a circular shape and include a diameter taken together with the release layer 215, defining a geometry of a second region 208 that defines the outlet orifice geometry of each pore of the porous membrane 201.

[0038] like Figure 2C As shown, the pillar template 200 is fabricated by first depositing an adhesion layer 212 of silicon dioxide onto a glass substrate 211. Then, a silicon pillar material layer 213 (e.g., 2-micron-thick i-Si or amorphous silicon) is deposited on the adhesion layer 212 and the substrate 211, as shown. Figure 2AAs shown. Although not shown, a hard mask (e.g., SiN or ITO) can be deposited on the silicon layer. A photoresist is deposited and patterned to form a photoresist pattern 214' defining pillars 213' in the pillar material layer 213. The pillar material layer 213 is etched down to the adhesion layer 212 to define a plurality of pillars 213' (e.g., 2.5 micrometer diameter), wherein the pillars have a substantially vertical profile.

[0039] The conditions used for etching column 213' must be controlled to leave an almost vertical sidewall profile. Figure 2B The substantially vertical profile of column 213' is shown to have an angle Ɵ relative to the horizontal plane ranging from 80° to 100°, more preferably from 85° to 95°, and most preferably about 90°. This angle is complementary to the angle of the substantially vertical profile of the second region 108.

[0040] Figure 3 This illustrates how plasma etching power and pressure can be controlled to produce the desired sidewall profile. As mentioned above, the pillars should be nearly vertical with a slightly concave shape to facilitate the removal of the final porous membrane from the pillar template. Figure 3 As shown, for i-Si layers, optimal results are obtained at 1000 W and 100 mT and 1300 W and 120 mT. The slope relative to the horizontal plane should be in the range of 80° to 100°, preferably in the range of 85° to 95°, and most preferably 90°. The pillar profile can be further controlled by varying the parameters of silicon deposition. For example, the pillar material can be deposited in a manner that results in different etch rates across the thickness of the silicon layer. For example, a step function of the deposition variable can be used to produce six different silicon layers with variable etch rates from top to bottom. This can include material with the fastest etch rate at the bottom and a slightly slower etch rate towards the top layers. Alternatively, a top layer with a slightly higher etch rate than the previous layer can be deposited to reduce protrusions. This technique can also be used to produce different etch rates across the thickness of the silicon nitride pillar material, as described in the embodiments disclosed herein.

[0041] Then, the column template 200 can be used to manufacture the porous membrane 201, such as... Figures 2D-2F As shown. An optional release layer 215 is deposited over the pillars 213' and the substrate 211. A polymer layer 202 (e.g., 10-micron polyimide) is first deposited on a pillar template 200, which includes a plurality of pillars 213' defining pores of the film material. The polymer layer 202 can be coated onto the pillar template using a coating process.

[0042] A hard mask layer 216 (e.g., 3500 angstrom silicon nitride) is deposited on top of the polymer layer 202, as... Figure 2DAs shown. A photoresist (not shown) is deposited on and patterned over a hard mask layer 216, and the hard mask layer 216 is etched through the patterned photoresist to provide an opening 205. The photoresist (not shown) is then stripped. The polymer layer 202 is etched (approximately 8 micrometers deep) through the patterned hard mask layer 216 until an optional release layer 215 in the region above pillar 213' is exposed through the opening 206, as shown. Figure 2E As shown. In the absence of the release layer 215, etching is performed until the top of the pillar 213' is exposed through the opening 206.

[0043] Then, wet etching is used to remove the hard mask layer 216. Then, wet etching is used to at least partially remove the release layer 215 on the column template 200 (if used), such as... Figure 2F As shown. The porous membrane 201 can then be removed from the column template 200. After another release layer 216 is deposited on the column template, the column template can then be reused to manufacture another porous membrane.

[0044] The porous membrane 201 according to this embodiment includes a polymer layer 202 having a bottom surface 203 and a top surface 204. A plurality of pores 205 extend through the polymer layer 202. Each pore has a first region 206 having a tapered profile 207 that opens wider at the intersection with the top surface 204 of the membrane; and a second region 208 having a substantially vertical profile 209 that intersects with the bottom surface 203 of the membrane. Figure 2F As shown, the tapered profile 207 can be a conical profile. A first region 206 intersects a second region 208 at an intermediate surface 210, which is exposed through an opening created by the first region 206. The intermediate surface 210 provides a buffer that allows for non-uniformity in etching and formation of different apertures in the first region, both within the same film and between separate fabrication runs of different films.

[0045] Porous membrane 401 is manufactured from column template 400. In one embodiment, the present invention relates to a method such as Figure 4C The column template 400 shown is used to manufacture a porous membrane 401. Manufacturing... Figure 4CThe method for constructing the pillar template 400 includes depositing an adhesion layer 412 (e.g., 2500 Å silicon dioxide) on a glass substrate 411. A pillar material layer 413 (e.g., 2 μm amorphous silicon) is deposited on the adhesion layer 412 and the substrate 411. Although not shown, a hard mask (e.g., SiN or ITO) may be deposited on the silicon layer. A photoresist 414 (2 μm) is deposited and patterned to define a circle with a diameter of 2.0 μm for defining the pillars 413'. The pillar material layer 413 is dry etched using anisotropic etching to fabricate vertical pillars 413' with a diameter of 1.5 μm (approximately 0.25 μm side undercut). Dry etching is performed until the adhesion layer 412 is exposed. A protective layer 415 (<1000 Å a-Si) is deposited on the patterned pillar material 413' and the adhesion layer 412.

[0046] Then, the column template 400 can be used to manufacture the porous membrane 401, such as... Figures 4D-4E As shown. The column template 400 includes multiple columns 413' defining pores of membrane material and a protective layer 415 deposited on the columns 413' and the adhesion layer 412, as shown. Figure 4C As shown. An optional release layer 416 (1000 Å ITO or SiN) is deposited on top of the protective layer 415. Then, a polymer 402 (e.g., 10 μm polyimide) is deposited on top of the optional release layer 416 on the column template 400.

[0047] A hard mask layer 417 (e.g., 2.0-micron silicon nitride) is deposited on top of the polymer layer 402, as... Figure 4D As shown. A photoresist (not shown) is deposited on and patterned over a hard mask layer 417, and the hard mask layer 417 is etched to provide an opening 418 by patterning the photoresist. The photoresist (not shown) is then stripped. The polymer layer 402 is etched (approximately 8 micrometers deep) through the patterned hard mask layer 417 until the release layer 416 in the region above the pillar 413' is exposed through the opening 406, as shown. Figure 4E As shown. Without the release layer 416, the polymer layer 402 is etched until the top of the pillar 413' is exposed through the opening 406.

[0048] The hard mask layer 417 is then removed using wet etching. If the release layer 416 is made of SiN, the step of removing the hard mask layer 417 will also remove the release layer. Otherwise, if the release layer is another material such as ITO, wet etching is used to at least partially remove the release layer. A structure with at least partial removal of the release layer 416 is shown below. Figure 4EIn the next step, the amount of wet over-etching may need to be adjusted to remove, but not completely delaminate, the membrane from the pillar during etching, allowing for controlled removal during subsequent delamination steps. Afterward, the porous membrane 401 is removed from the pillar template 400. The pillar template can then be reused to fabricate another porous membrane.

[0049] The porous membrane 401 according to this embodiment includes a polymer layer 402 having a bottom surface 403 and a top surface 404. A plurality of pores 405 extend through the polymer layer 402. Each pore has a first region 406 having a tapered profile 407 that opens wider at the intersection with the top surface 404 of the membrane; and a second region 408 having a substantially vertical profile 409 that intersects with the bottom surface 403 of the membrane. Figure 4E As shown, the tapered profile 407 can be a conical profile. A first region 406 intersects a second region 408 at an intermediate surface 410, which is exposed through an opening created by the first region 406. The intermediate surface 410 provides a buffer that allows for non-uniformity in etching and formation of different apertures in the first region, both within the same film and between separate fabrication runs of different films.

[0050] Porous membrane 501 is manufactured using column template 500. In one embodiment, the present invention relates to a method such as Figure 5C The pillar template 500 shown fabricates a porous film 500. A method for fabricating the pillar template 500 includes depositing a pillar material layer 513 (e.g., 2.0 micrometer silicon nitride) on a glass substrate 511. Although not shown, a hard mask (e.g., PECVD oxide) can be deposited on the silicon layer. The pillar profile can be controlled by varying the parameters of the silicon nitride deposition. For example, the pillar material can be deposited at different etch rates that result in varying thicknesses across the silicon nitride layer. For example, a step function of the deposition variables can be used to produce six different silicon nitride layers with variable etch rates from top to bottom. This can include material with the fastest etch rate at the bottom and a slightly slower etch rate towards the top layers. Alternatively, a top layer with a slightly higher etch rate than the previous layer can be deposited to reduce protrusions.

[0051] A photoresist 514 (2 μm) is deposited and patterned to define a circle with a diameter of 2.0 μm. Anisotropic dry etching is used to etch the pillar material layer 513 to fabricate vertical pillars 513' with a diameter of 1.5 μm (approximately 0.25 μm side undercut). Dry etching is performed until the glass substrate 511 is exposed. A protective layer 515 (<1000 Å a-Si) is deposited on the patterned pillar material 513' and adhered to the glass substrate 511.

[0052] In one embodiment, the present invention relates to a method for manufacturing a porous membrane 501 using a column template, such as Figures 5D-5EAs shown. The pillar template 500 includes multiple pillars 513' defining pores of film material and a protective layer 515 deposited on the pillars 513' and the glass substrate 511, as shown. Figure 5C As shown. An optional release layer 516 (1000 Å ITO or SiN) is deposited on top of the protective layer 515. Then, a polymer 502 (e.g., 10 μm polyimide) is deposited on top of the optional release layer 516 on the column template 500.

[0053] A hard mask layer 517 (e.g., 3000 angstrom silicon nitride) is deposited on top of the polymer layer 502, as... Figure 5D As shown. A photoresist (not shown) is deposited on and patterned over a hard mask layer 517, and the hard mask layer 517 is etched through the patterned photoresist to provide an opening 518. The photoresist (not shown) is then stripped. The polymer layer 502 is etched (approximately 8 micrometers deep) through the patterned hard mask layer 517 until the release layer 516 in the region above the pillar 513' is exposed through the opening 506, as shown. Figure 5E As shown. Without the release layer 516, the polymer layer 502 is etched until the top of the pillar 513' is exposed through the opening 506.

[0054] The hard mask layer 417 is then removed using wet etching. If the release layer 516 is made of SiN, the step of removing the hard mask layer 517 will also remove the release layer. Otherwise, if the release layer is another material such as ITO, wet etching is used to at least partially remove the release layer. A structure with at least partial removal of the release layer 516 is shown below. Figure 5E In the next step, the amount of wet over-etching may need to be adjusted to remove, but not completely delaminate, the membrane from the pillar during etching, allowing for controlled removal during subsequent delamination steps. Afterward, the porous membrane 501 is removed from the pillar template 500. The pillar template can then be reused to fabricate another porous membrane.

[0055] The porous membrane 501 according to this embodiment includes a polymer layer 502 having a bottom surface 503 and a top surface 504. A plurality of pores 505 extend through the polymer layer 502. Each pore has a first region 506 having a tapered profile 507 that opens wider at the intersection with the top surface 504 of the membrane; and a second region 508 having a substantially vertical profile 509 that intersects with the bottom surface 503 of the membrane. Figure 5E As shown, the tapered profile 507 can be a conical profile. A first region 506 intersects a second region 508 at an intermediate surface 510, which is exposed through an opening created by the first region 506. The intermediate surface 510 provides a buffer that allows for non-uniformity in etching and formation of different apertures in the first region, both within the same film and between separate fabrication runs of different films.

[0056] Porous membrane 601 is manufactured using column template 600. In one embodiment, the present invention relates to the use of, for example Figure 6D The pillar template 600 shown fabricates a porous membrane 601. The method includes depositing a hard mask layer 612 (e.g., 700-1400 Å ITO) on a glass substrate 611. Other hard mask materials, such as a-Si, can be used. Additionally, the hard mask may be optional if the photoresist can withstand dry etching of the glass substrate described below. The photoresist is deposited and patterned to define pillars with a diameter of 3.5-8.5 micrometers, as shown. Figure 6A As shown. If a hard mask layer 612 is used, the material is wet-etched (0.25-0.75 μm side undercut) using a patterned photoresist to produce a patterned hard mask 612' (2.0 to 8.0 μm diameter), as shown. Figure 6B As shown.

[0057] The glass substrate 611 is then dry-etched to a depth of approximately 2 micrometers using highly anisotropic etching. Given that the pillar 611' is expected to have a diameter of less than 2 micrometers, the previous anisotropic etching step is performed to remove 1.6 micrometers instead of 2.0 micrometers. Then, highly isotropic etching is performed to remove the final 0.4 micrometers, as... Figure 6C As shown. After glass etching is completed, a hard mask layer 612 is used in conjunction with wet etching. A protective overlay layer 615 is used to complete the pillar template, which is preferably a thin bilayer of 500 Å SiOx followed by 1000 Å i-Si on a patterned glass substrate. The i-Si protects the glass pillar from BOE etching, where the hard mask and release layer are removed. Figure 6D The column template 600 shown can be reused multiple times.

[0058] In one embodiment, the present invention relates to a method for manufacturing a porous membrane 601 using a column template, such as Figures 6E-6F As shown. The column template 600 includes multiple columns 613' defining pores of membrane material and a protective layer 616 deposited on the columns 613' and the protective layer 615, as shown. Figure 6E As shown. An optional release layer 616 (e.g., 500 Å SiN) is deposited on top of the protective layer 615. Then, a polymer 602 (e.g., 10 μm polyimide) is deposited on top of the optional release layer 616 on the column template 600.

[0059] A hard mask layer 617 (e.g., 3000 angstrom silicon nitride) is deposited on top of the polymer layer 602, as... Figure 6EAs shown. A photoresist (not shown) is deposited on and patterned over a hard mask layer 617, and the hard mask layer 617 is etched through the patterned photoresist to provide an opening 618. The photoresist (not shown) is then stripped. The polymer layer 602 is etched (approximately 8 micrometers deep) through the patterned hard mask layer 617 until the release layer 616 in the region above the pillar 613' is exposed through the opening 606, as shown. Figure 6F As shown. Without the release layer 616, the polymer layer 602 is etched until the top of the pillar 613 is exposed through the opening 606.

[0060] The hard mask layer 617 is then removed using wet etching. If the release layer 616 is made of SiN, the step of removing the hard mask layer 617 will also remove the release layer. Otherwise, if the release layer is another material such as ITO, wet etching is used to at least partially remove the release layer. A structure with at least partial removal of the release layer 616 is shown below. Figure 6F In the next step, the amount of wet over-etching may need to be adjusted to remove, but not completely delaminate, the membrane from the pillar during etching, allowing for controlled removal during subsequent delamination steps. Afterward, the porous membrane 601 is removed from the pillar template 600. The pillar template can then be reused to fabricate another porous membrane.

[0061] The porous membrane 601 according to this embodiment includes a polymer layer 602 having a bottom surface 603 and a top surface 604. A plurality of pores 605 extend through the polymer layer 602. Each pore has a first region 606 having a tapered profile 607 that opens wider at the intersection with the top surface 604 of the membrane; and a second region 608 having a substantially vertical profile 609 that intersects with the bottom surface 603 of the membrane. Figure 6F As shown, the tapered profile 607 can be a conical profile. A first region 606 intersects a second region 608 at an intermediate surface 610, which is exposed through an opening created by the first region 606. The intermediate surface 610 provides a buffer that allows for non-uniformity in etching and formation of different apertures in the first region, both within the same film and between separate fabrication runs of different films.

[0062] Other embodiments and uses of the invention will be apparent to those skilled in the art in light of the description and practice of the invention disclosed herein. All references cited herein (including all U.S. and foreign patents and patent applications) are expressly and entirely incorporated herein by reference. This specification and the embodiments are intended to be exemplary only, and the true scope and spirit of the invention are indicated by the appended claims.

Claims

1. A porous membrane (101), comprising: A polymer layer (102) defining the bottom surface (103) and the top surface (104) of the membrane; A plurality of pores (105) extending through the polymer layer (102) are provided, each pore (105) having a first region (106) and a second region (108), the first region having a tapered profile (107) that opens wider at its intersection with the top surface (104) of the membrane, the second region having a substantially vertical profile (109) that intersects with the bottom surface (103) of the membrane, the first region (106) intersecting the second region (108) at an intermediate surface (110) that faces exposure through the opening created by the first region (106).

2. The porous membrane (101) according to claim 1, wherein the substantially vertical profile has an angle ranging from 80° to 100° from the horizontal plane.

3. The porous membrane (101) according to claim 1 or claim 2, wherein the substantially vertical profile has an angle ranging from 85° to 95° from the horizontal plane.

4. The porous membrane (101) according to any of the preceding claims, wherein the intermediate surface of each pore has a surface area that varies between the pores to a greater extent than the surface area of ​​the opening defined by the second region.

5. The porous membrane (101) according to any of the preceding claims, wherein the first region has a conical profile.

6. The porous membrane (101) according to any of the preceding claims, wherein the membrane includes a pore region containing the pores and a tear-resistant ring surrounding the pore region.

7. The porous membrane (101) according to any one of the preceding claims, wherein the membrane layer comprises at least one material selected from at least one of polyimide, polyamide, polycarbonate, polyetherimide, polyetherketone, polyurethane, synthetic polymer, low-density polyethylene (LDPE), high-density polyethylene (HDPE), polypropylene (PP), polyvinyl chloride (PVC), polystyrene (PS), nylon, Teflon (polytetrafluoroethylene), thermoplastic polyurethane (TPU), polyethylene, acrylate polymers, acrylate monomers and / or acrylate elastomers.

8. The porous membrane (101) according to any of the preceding claims, wherein the membrane layer is polyimide.

9. The porous membrane (101) according to any of the preceding claims, wherein the membrane has a thickness in the range of 3 to 50 micrometers.

10. The porous membrane (101) according to any one of the preceding claims, wherein the membrane has a porous structure of at least 0.1 μm. 2 Surface area.

11. The porous membrane (101) according to any of the preceding claims, wherein the membrane includes a tear-resistant ring surrounding its periphery.

12. A column template (200, 400, 500, 600) for manufacturing porous membranes, comprising: Substrates (211, 411, 511, 611); and Multiple pillars (213', 413', 513', 613') protrude from the substrate at a first height and have a lateral dimension, the pillars corresponding to the pore region of the porous membrane and having a substantially vertical profile; The first height is in the range of 0.5 to 5 micrometers, and the lateral dimension is in the range of 1 to 5 micrometers.

13. The column template (200, 400, 500, 600) according to claim 12, wherein the first height is in the range of 1.5 to 2.5 micrometers and the lateral dimension is in the range of 1.5 to 3 micrometers.

14. The column template (200, 400, 500, 600) according to claim 12 or 13, wherein the substantially vertical profile has an angle ranging from 85° to 95° from the horizontal plane, and the plurality of columns have different etching rates over the entire thickness of the column.

15. The column template (200, 400, 500, 600) according to any one of claims 12 to 14, wherein the substrate (211, 411) is a glass substrate, and the plurality of columns (213', 413') comprise silicon, and the column template further comprises an adhesion layer (212, 412) on the glass substrate (211, 411).

16. The column template (200, 400, 500, 600) according to claim 15, wherein the column template includes a region lacking columns surrounding a region having columns, the region lacking columns corresponding to a tear-resistant ring in a membrane to be formed by the column template.

17. The column template (200, 400, 500, 600) according to claim 15 or 16, wherein the column template further comprises a protective layer (415) on top of the adhesive layer (412) in the region between the plurality of columns.

18. The column template (200, 400, 500, 600) according to claim 17, wherein the protective layer comprises silicon.

19. The pillar template (200, 400, 500, 600) according to any one of claims 12 to 18, wherein the substrate (511) is a glass substrate, and the plurality of pillars (513') comprise silicon nitride, and the pillar template further comprises a protective layer (515) on the glass substrate (511) in the region between the plurality of pillars.

20. The column template (200, 400, 500, 600) according to any one of claims 12 to 19, wherein the substrate (611) is a glass substrate, and the plurality of columns (613') are glass protrusions integral with the glass substrate, and the column template further includes a protective layer (615) on the glass substrate (611) in the region between the plurality of columns (613') and the plurality of columns.

21. The column template (200, 400, 500, 600) according to claim 20, wherein the protective layer comprises a silicon dioxide layer coated on the glass substrate (611) in the region between the plurality of columns (613') and the plurality of columns, and a silicon layer on the silicon dioxide layer of the protective layer.

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