Filters for microprocessing or semiconductor processing fluids

Abstract

Described are filters and filter products that contain a microporous membrane for filtration, wherein at least one layer of the membrane has an average pore size less than 0.035 microns; the filter or filter product and its membrane may be used in an ultra-filtration or nano-filtration process such as for processing microelectronics or semiconductor processing fluids.

Description

FILTERS FOR MICROPROCESSING OR SEMICONDUCTOR PROCESSING FLUIDSCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application is a continuation-in-part of International Patent Application No. PCT / US2022 / 043676, filed on September 15, 2022, which claims priority to U.S.Provisional Patent Application No. 63 / 246,093, filed on September 20, 2021, and U.S. Provisional Patent Application No. 63 / 343,347, filed on May 18, 2022. The entire contents of each of the above-referenced applications are hereby incorporated by reference in their entirety.FIELD

[0002] This application is directed to filters and filter products for processing microelectronics or semiconductor processing fluids and that include dry-process membranes suitable for use in filtration processes, and methods of using the filter products. Such processes may involve ultrafiltration or nano-filtration.BACKGROUND

[0003] Filters with polymeric, microporous filter membranes are used in various applications to remove unwanted materials from a flow of a useful fluid. Many gaseous and liquid fluids in industry are processed using filters, including environmental air, drinking water, fuels, liquid industrial solvents and processing fluids, industrial gases used for manufacturing or processing, liquids that have medical or pharmaceutical uses, and solvents and processing fluids used in microprocessor and semiconductor fabrication.

[0004] Unwanted materials that are removed from fluids include impurities and contaminants such as particles, microorganisms, and dissolved chemical species. Specific examples of impurity removal applications for filter membranes include their use to remove particles or bacteria from therapeutic solutions in the pharmaceutical industry, to process ultrapure aqueous and organic solvent solutions for use in microelectronics processing, and for air and water purification processes. Nano-filtration and / or ultra-filtration are often used in these processes. It is desirable that membranes for nano-filtration and ultra-filtration exhibit one or more of the following properties: mechanical stability, dimensional stability, flow rate suitable for commercial use, low contaminants, etc. Improvements in any or all of these areas are desirable.SUMMARY

[0005] Filter products and microporous membranes for use therein for filtration, such as in filters or filter products for processing microelectronics or semiconductor processing fluids, arc described herein. In some embodiments, at least one layer of the membrane, referred to as a "tight layer," has an average pore size less than 0.035 microns and a thickness less than 14 microns. The average pore size of the tight layer, in some embodiments, may be less than 0.03 microns, less than 0.025 microns, or less than 0.020 microns. In some preferred embodiments, the average pore size of the tight layer may be from about 0.010 to about 0.020 microns. In some embodiments, the average pore size of the tight layer may be less than 0.035 microns and the thickness of the tight layer may be less than 12 microns. In some embodiments, the average pore size of the tight layer may be less than 0.035 microns and the thickness of the layer may be less than 10 microns. The average pore size may be measured using an Aquapore device available through PMI (Porous Materials Inc.). Average pore size is expressed in microns or pm.

[0006] In some embodiments the tight layer, may be a polypropylene-containing layer, while in other embodiments the tight layer may be a polyethylene-containing layer.

[0007] In some embodiments described above, the membrane may be a monolayer membrane, a bilayer membrane, a tri-layer membrane, or a multi-layer membrane. The bi-layer, tri-layer, or multi-layer membranes may be formed by laminating two or more layers, coextruding two or more layers, or a combination of lamination and extrusion steps.

[0008] In some of the embodiments described above, the membrane may be a tri-layer membrane comprising a polypropylene-containing layer, a polyethylene-containing layer, and a polypropylene-containing layer in that order. In some embodiments described above, the membrane may be a tri-layer membrane comprising a polyethylene-containing layer, a polypropylene-containing layer, and a polyethylene-containing layer.

[0009] In some embodiments described hereinabove, the thickness of the membrane is less than 14 microns, less than 12 microns, or less than 10 microns.

[0010] In some embodiments, the membrane is translucent or transparent. In some embodiments, the membrane may have a blue tint and be translucent or transparent.

[0011] In some embodiments described hereinabove, shrinkage of the membrane at 90°C for 1 hour is less than 25%, less than 20%, less than 15%, less than 10%, or less than 5%.

[0012] In some embodiments described hereinabove, the membrane has a flow time from 400 to 40,000 seconds. Flow time may be measured using isopropyl alcohol (IPA), wherein the flow time is the time to flow 500 ml of isopropyl alcohol at a temperature of 21oC and a pressure of 0.1 MPa through a 47 mm disc of the membrane having an area of 12.5 cm2.

[0013] In some embodiments, the membrane may have a hydrophilic treatment or coating on at least one side thereof. This may improve filtering performance when removing contaminants from a liquid that includes water or alcohol.

[0014] In some embodiments the membrane may be treated to improve filtering performance, specifically non-sieving filtering performance, of the membrane. Porous membranes can remove contaminants from a fluid by either or both of a sieving mechanism and a non-sieving mechanism. By a sieving mechanism, contaminants (e.g., particles) that are larger than a pore of a membrane are mechanically prevented from passing through the membrane, and become trapped within the membrane and removed from a fluid passing through the membrane. By a non-sieving mechanism, impurities that are smaller than the pores of a membrane are attracted to the membrane surface via a chemical or electrostatic interaction and are held within the membrane and removed from a fluid flowing through the membrane. A membrane as described may be modified or treated to add chemical species to surface of the pores of the membrane, including at internal pore surfaces, that attract contaminants by an electrostatic or chemical interaction. Chemical species that are effective to improve non-sieving filtering performance of a membrane may be added to the membrane surface by coating the surface with a coating that contains the chemical species. The coating may be applied to the surface and may optionally be crosslinked after being applied to the surface. By other methods, the chemical species may be chemically attached to, e.g., grafted onto, the polymer of the membrane.

[0015] In another aspect, an ultra-filtration or a nano-filtration process is described. One step of the process is filtering a fluid (e.g., a solvent useful in microelectronics and semiconductor processing) through the membrane, which may be contained in a filter product described herein.

[0016] In another aspect, a filter product is described which comprises a treated or modified membrane as described, contained in or supported by a frame or a housing.

[0017] In another aspect, the invention relates to a filter or filter product for processing microelectronics or semiconductor processing fluids. The filter product includes: a housinghaving an inlet and an outlet and a multi-layer microporous membrane supported between the inlet and the outlet. The multi-layer microporous membrane includes: a first polyolefin layer and a second polyolefin layer. The second polyolefin layer includes mono-axially oriented micropores having an average pore size less than 0.035 microns.

[0018] In another aspect, the invention relates to a method of using a filter or filter product as described by passing liquid fluid through the filtration membrane of the filter or filter product to remove an impurity or contaminant from the liquid fluid.BRIEF DESCRIPTION OF THE DRAWING

[0019] Figure 1 is an SEM of a dry -process microporous membrane for a filter or filter product as described herein.

[0020] Figure 2 is an illustration of a membrane for a filter or filter product as described.

[0021] Figure 3 is an illustration of a membrane for a filter or filter product as described.

[0022] Figure 4 shows an example filter product (cartridge) as described.

[0023] Figure 5 shows an example filter product as described.DETAILED DESCRIPTION

[0024] The subject matter of aspects of the present disclosure is described with specificity herein to meet statutory requirements. However, the description itself is not intended to limit the scope of this patent. Rather, the inventors have contemplated that the claimed subject matter might also be embodied in other ways, to include different steps or combinations of steps similar to the ones described in this document, in conjunction with other present or future technologies. Moreover, although the term “step” can be used herein to connote different elements of methods employed, the terms should not be interpreted as implying any particular order among or between various steps disclosed herein unless and except when the order of individual steps is explicitly described.

[0025] Accordingly, embodiments described herein can be understood more readily by reference to the following detailed description, examples, and figures. Elements, apparatus, and methods described herein, however, are not limited to the specific embodiments presented in the detailed description, examples, and figures. It should be recognized that the exemplaryembodiments herein are merely illustrative of the principles of the invention. Numerous modifications and adaptations will be readily apparent to those of skill in the art without departing from the spirit and scope of the invention.

[0026] In addition, all ranges disclosed herein are to be understood to encompass any and all subranges subsumed therein. For example, a stated range of “1.0 to 10.0” should be considered to include any and all subranges beginning with a minimum value of 1.0 or more and ending with a maximum value of 10.0 or less, e.g., 1.0 to 5.3, or 4.7 to 10.0, or 3.6 to 7.9.

[0027] All ranges disclosed herein are also to be considered to include the end points of the range, unless expressly stated otherwise. For example, a range of “between 5 and 10” or “5 to 10” or “5-10” should generally be considered to include the end points 5 and 10.

[0028] Further, when the phrase “up to” is used in connection with an amount or quantity; it is to be understood that the amount is at least a detectable amount or quantity. For example, a material present in an amount “up to” a specified amount can be present from a detectable amount and up to and including the specified amount.

[0029] Additionally, in any disclosed embodiment, the terms “substantially,” “approximately,” and “about” may be substituted with “within [a percentage] of’ what is specified, where the percentage includes 0.1, 1, 5, and 10 percent.

[0030] The following describes filtration membranes (or “filter membranes”) that are useful in filters and filter products such as cartridges that contain the modified or treated filter membranes, and methods of using the filter membranes and filter products for filtering a liquid fluid. The filters membranes comprise, consist of, or consist essentially of microporous polyolefin membranes that are effective for filtering (removing contaminants from) liquid fluids, including liquid fluids that are used in a process of manufacturing microelectronic or semiconductor devices, sometimes referred to as “microelectronics or semiconductor processing fluids.” The membranes exhibit useful flow properties (e.g., flow rate, flow time, bubble point) of a liquid through the membrane in combination with effective particle removal properties (e.g., retention of various sizes of particles), to provide efficient filtering performance of the membrane.

[0031] Filter membranes and filter products (including filter components such as cartridges) that contain the filter membrane can be useful in methods of filtering a liquid chemical material to remove unwanted material (contaminants, impurities) from the liquid chemical material,especially to produce a highly pure liquid chemical material that is useful for performing a process used during manufacturing of microelectronic or semiconductor devices. Example filters and filter products can be used for removing contaminants or impurities from a liquid chemical that is used or useful in a step of processing a semiconductor or microelectronic device (e.g., a microelectronic substrate or a semiconductor substrate) such as for filtering a liquid solvent or other process liquid that is used in a method, including: semiconductor photolithography, a wet etching or cleaning step, a method of forming spin-on-glass (SOG), for a backside anti-reflective coating (BARC) method, etc.

[0032] Some specific, non-limiting, examples of liquid chemical materials that can be filtered using a filter membrane or filter product as described include: n-butyl acetate (nBA), isopropyl alcohol (IPA), 2-ethoxyethyl acetate (2EEA), cyclohexanone, ethyl lactate, gammabutyrolactone, hexamethyldisilazane, methyl-2-hydroxyisobutyrate, methyl isobutyl carbinol (MIBC), n-butyl acetate, methyl isobutyl ketone (MIBK), isoamyl acetate, propylene glycol monoethyl ether, propylene glycol methyl ether (PGME), 2-heptanone, and propylene glycol monomethyl ether acetate (PGMEA).

[0033] A membrane as described contains at least one layer that may be referred to as a “tight” layer or a “retentive” layer that comprises polyolefin polymer and that includes pores of an average pore size of less than 0.035 microns, wherein the pores are elongate pores having an aspect ratio of greater than 1.0, 1.2, 1.5, 2.0, or 3.0 due to the membrane being extended or stretched uniaxially (mono-axially, as opposed to bi-axially).

[0034] The pores of the membrane form an open pore structure that includes pores that are distributed throughout and across the thickness of the membrane, including multiple layers of a membrane, and are arranged with different pore sizes and different average pore sizes being present at different portions of the membrane, i.e., at different “layers” of the membrane.

[0035] Example membranes include multiple layers that include a first layer (sometimes referred to as a “tight” layer or a “retentive” layer) that includes relatively small pores, and a second layer (an “open” layer or a “support” layer) that includes relatively larger pores compared to the pores of the tight layer. The tight layer has smaller pores, higher retention properties, and due to the smaller pores can exhibit higher resistance to flow through the membrane. The tight layer exhibits a higher resistance to flow relative to the open layer and inhibits the flow of liquid through the filter membrane to a greater degree than does an open layer. An open layer hasrelatively larger pores, lower retention properties, causes less resistance to flow (relative to the tight layer), and allows for a relatively higher rate of flow of liquid through that layer of the filter membrane.

[0036] A tight layer of a membrane functions as a retentive portion of the membrane and is responsible for physically retaining (catching) and removing particles or impurities from a liquid fluid as the fluid passes through the pores of the membrane. The tight layer can effectively function as a retentive portion of the membrane without being unduly or excessively thick. A tight layer that is less thick (i.e., that is thinner) will introduce a relatively reduced resistance to flow of liquid through the membrane, and can therefore be advantageous by allowing higher flow. Accordingly, porous membranes as described can be made to include a tight layer that is relatively thin (that has a lower thickness) compared to the thickness of the open layer of the membrane.

[0037] An open layer of the membrane functions to support the tight layer, and desirably is less restrictive to flow of liquid through the membrane. The average size of the pores of an open layer will be greater than the average size of pores of the tight layer.

[0038] Sizes of pores of a multi-layer membrane may differ at different layers of the membrane, with pores of a tight layer being smaller than pores of an open layer. Pores of different layers of a membrane may have different average sizes to provide a combination of useful filtering properties (e.g., as measured by retention) and desirable flow properties (e.g., as measured by flow time). Example average pore sizes of a membrane may be in a range sometimes classified as “microporous,” “ultraporous,” or “nanoporous”; for purposes of the present description and claims, the term “microporous” is sometimes used to refer to pores within any of these size ranges, including microporous and sub-microporous sizes, as a way of distinguishing from materials having larger pore sizes, i.e., to distinguish over materials that are considered to be “macroporous.”

[0039] According to example membranes, an average pore size of a tight layer may be less than 0.035 microns, less than 0.03 microns, less than 0.025 microns, or less than 0.020 microns, e.g., in a range from about 0.010 to about 0.020 microns. According to example membranes, an average pore size of an open layer may be in these same ranges or larger but will be larger than the pores of the tight layer. For example, an average pore size of an open layer may be at least0.010 microns, at least 0.020 microns, at least 0.030 microns, e.g., in a range from about 0.010 to about 0.20 microns.

[0040] Pore size of a membrane may be measured directly or indirectly, by known techniques. By one example, average pore size of a tight layer may be measured by correlation to a measured bubble point of a membrane or a membrane layer, or using doing BP or using liquid-liquid porosimetry techniques. Average pore size of an open layer may be measured by surface scanning electron microscope (SEM) techniques.

[0041] Example membranes include a tight layer that has a thickness that is less than a thickness of an open layer, for example based on the tight layer being prepared to contain a lower amount (based on mass or volume per area) of polymer compared to the amount of polymer in the open layer. Example thicknesses of a tight layer may be less than 14 microns, e.g., as described elsewhere herein.

[0042] Example total thicknesses of an membrane, e.g., of all (two, three, four, etc.) polyolefin layers of a membrane may be less than 20 microns, as described elsewhere herein.

[0043] Example membranes may comprise, consist of, or consist essentially of polyolefin layers that include: a single polyolefin layer that is a tight layer only with no additional polyolefin layers; two polyolefin layers that include a tight layer and an open layer only with no additional polyolefin layers; or three polyolefin layers that include a tight layer and two open layers only, with no additional polyolefin layers, with the tight layer being located between the two open layers.

[0044] A membrane that is a multi-layer membrane that includes a tight polyolefin layer and one or more open polyolefin layers may include (comprise, consist of, or consist essentially) a tight layer that contains polypropylene and one or two open layers that contain polyethylene. Alternately, a multi-layer membrane may include a tight polyolefin layer and one or more open polyolefin layers that include (comprise, consist of, or consist essentially) a tight layer that contains polyethylene and one or two open layers that contain polypropylene.

[0045] An example tight layer may contain (comprise, consist essentially of, or consist of) polypropylene, and may be referred to as a “polypropylene layer” or as a “polypropylene- containing layer.” Example tight layers can contain at least 50, 60, 70, 80, 90, 95, 98, or 99 percent by weight polypropylene polymer (homopolymer or co-polymer) based on total weight polymer in the tight layer.

[0046] An example tight layer may contain (comprise, consist essentially of, or consist of) polyethylene, and may be referred to as a “polyethylene layer” or as a “polycthylcnc-containing layer.” Example tight layers can contain at least 50, 60, 70, 80, 90, 95, 98, or 99 percent by weight polyethylene polymer (homopolymer or co-polymer) based on total weight polymer in the tight layer.

[0047] An example open layer may contain (comprise, consist essentially of, or consist of) polypropylene, and may be referred to as a “polypropylene layer” or as a “polypropylene- containing layer.” Example open layers can contain at least 20, 30, 40, 50, 60, 70, 80, 90, 95, 98, or 99 percent by weight polypropylene polymer (homopolymer or co-polymer) based on total polymer in the tight layer.

[0048] An example open layer may contain (comprise, consist essentially of, or consist of) polyethylene, and may be referred to as a “polyethylene layer” or as a “polyethylene-containing layer.” Example open layers can contain at least 20, 30, 40, 50, 60, 70, 80, 90, 95, 98, or 99 percent by weight polyethylene polymer (homopolymer or co-polymer) based on total polymer in the tight layer.

[0049] The term “polypropylene” refers to a polymer that has, in part or substantially, a molecular structure of repeating -CH-CH(CH i)- units. Polypropylene can be made by reacting monomer composition that includes monomers that comprise, consist of, or consist essentially of propylene monomers. Thus, a polypropylene polymer may be a polypropylene homopolymer prepared by reacting monomers that consist of or consist essentially of propylene monomers. Alternatively, a polypropylene polymer may be a polypropylene copolymer prepared by reacting a combination of propylene and non-propylene monomers that include, consist of, or consist essentially of propylene monomers in combination with another type of monomer such as another alpha-olefin monomer, e.g., ethylene, butene, hexene, or octane, or a combination of these; for a polypropylene copolymer, the amount of propylene monomer used to produce the copolymer, relative to non-propylene monomers, can be any useful amount, such as an amount of at least 50, 60, 70, 80, 90, 95, or 99 percent (by weight) propylene monomer per total weight of all monomers (propylene monomer and non-propylene monomer) in a monomer composition used to prepare the propylene copolymer.

[0050] The term “polyethylene” refers to a polymer that has, in part or substantially, a linear molecular structure of repeating -CH2-CH2- units. Polyethylene can be made by reactingmonomer composition that includes monomer that comprise, consist of, or consist essentially of ethylene monomers. Thus, a polyethylene polymer may be a polyethylene homopoly mcr prepared by reacting monomers that consist of or consist essentially of ethylene monomers. Alternatively, a polyethylene polymer may be a polyethylene copolymer prepared by reacting a combination of ethylene and non-ethylene monomers that include, consist of, or consist essentially of ethylene monomers in combination with another type of monomer such as another alpha-olefin monomer, e.g., butene, hexene, or octane, or a combination of these; for a polyethylene copolymer, the amount of ethylene monomer used to produce the copolymer, relative to non-ethylene monomers, can be any useful amount, such as an amount of at least 50, 60, 70, 80, 90, 95, or 99 percent (by weight) ethylene monomer per total weight of all monomers (ethylene monomer and non-ethylene monomer) in a monomer composition used to prepare the ethylene copolymer.

[0051] As used herein, a composition (e.g., monomer composition or polymer composition of a membrane layer) that is described as “consisting essentially of’ a certain ingredient or a combination of specified ingredients is a composition that contains the ingredient or combination of specified ingredients and not more than a small or insignificant amount of other materials, e.g., not more than 3, 2, 1, 0.5, 0.1, or 0.05 weight percent of any other ingredient or combination of ingredients. A monomer composition or polymeric layer of a membrane that is described as containing monomers or polymer that “consists essentially of’ ethylene monomers, propylene monomers, ethylene polymer, propylene polymer or the like, is a monomer or polymer composition that contains ethylene or propylene monomers, or ethylene or propylene polymer (including copolymers as described) and not more than a small or insignificant amount of other material, e.g., not more than 3, 2, 1, 0.5, 0.1, or 0.05 weight percent of any other monomer or polymer.

[0052] The membrane is of a type that is referred to as a “dry-process” microporous membranes. In some embodiments, at least one layer of the membrane is a tight layer that has an average pore size less than 0.035 microns and a thickness less than 14 microns, less than 13 microns, less than 12 microns, less than 11 microns, less than 10 microns, less than 9 microns, less than 8 microns, less than 7 microns, less than 6 microns, less than 5 microns, less than 4 microns, less than 3 microns, less than 2 microns, or less than 1 microns. In some embodiments, at the least one tight layer of the membrane has an average pore size less than 0.030 microns anda thickness less than 14 microns, less than 13 microns, less than 12 microns, less than 11 microns, less than 10 microns, less than 9 microns, less than 8 microns, less than 7 microns, less than 6 microns, less than 5 microns, less than 4 microns, less than 3 microns, less than 2 microns, or less than 1 microns. In some embodiments, the at least one tight layer of the membrane has an average pore size less than 0.025 microns and a thickness less than 14 microns, less than 13 microns, less than 12 microns, less than 11 microns, less than 10 microns, less than 9 microns, less than 8 microns, less than 7 microns, less than 6 microns, less than 5 microns, less than 4 microns, less than 3 microns, less than 2 microns, or less than 1 microns. In some embodiments, the at least one tight layer of the membrane has an average pore size less than 0.020 microns and a thickness less than 14 microns, less than 13 microns, less than 12 microns, less than 11 microns, less than 10 microns, less than 9 microns, less than 8 microns, less than 7 microns, less than 6 microns, less than 5 microns, less than 4 microns, less than 3 microns, less than 2 microns, or less than 1 microns. In some embodiments, at least one layer of the membrane has an average pore size less than 0.015 microns and a thickness less than 14 microns, less than 13 microns, less than 12 microns, less than 11 microns, less than 10 microns, less than 9 microns, less than 8 microns, less than 7 microns, less than 6 microns, less than 5 microns, less than 4 microns, less than 3 microns, less than 2 microns, or less than 1 microns. In some embodiments, the at least one tight layer of the membrane has an average pore size less than 0.010 microns and a thickness less than 14 microns, less than 13 microns, less than 12 microns, less than 11 microns, less than 10 microns, less than 9 microns, less than 8 microns, less than 7 microns, less than 6 microns, less than 5 microns, less than 4 microns, less than 3 microns, less than 2 microns, or less than 1 microns. In some embodiments, at least one layer of the membrane has an average pore size less than 0.005 microns and a thickness less than 14 microns, less than 13 microns, less than 12 microns, less than 11 microns, less than 10 microns, less than 9 microns, less than 8 microns, less than 7 microns, less than 6 microns, less than 5 microns, less than 4 microns, less than 3 microns, less than 2 microns, or less than 1 microns. In some preferred embodiments, the at least one tight layer of the membrane has an average pore size from about 0.010 to about 0.020 microns, and a thickness less than 14 microns, less than 13 microns, less than 12 microns, less than 11 microns, less than 10 microns, less than 9 microns, less than 8 microns, less than 7 microns, less than 6 microns, less than 5 microns, less than 4 microns, less than 3 microns, less than 2 microns, or less than 1 microns.

[0053] In some embodiments described herein above, at least one tight layer may be a tight layer that comprises polypropylene, i.c., is a polypropylcnc-containing layer. In some embodiments described herein above, at least one layer may be a tight layer that comprises polyethylene, i.e., is a polyethylene-containing layer.

[0054] In some embodiments described above, the membrane may be a monolayer membrane, a bilayer membrane, a tri-layer membrane, or a multi-layer membrane, any of which includes at least one tight layer as described. A multi-layer membrane may have four or more layers. The bi-layer, tri-layer, or multi-layer membranes may be formed by laminating two or more layers, co-extruding two or more layers, or a combination of lamination and extrusion steps.

[0055] In some embodiments, the membrane may have a total thickness of less than 20 microns, less than 19 microns, less than 18 microns, less than 17 microns, less than 16 microns, less than 15 microns, less than 14 microns, less than 13 microns, less than 12 microns, less than 11 microns, less than 10 microns, less than 9 microns, less than 8 microns, less than 7 microns, less than 6 microns, less than 5 microns, less than 4 microns, less than 3 microns, less than 2 microns, or less than 1 micron.

[0056] For example, in one embodiment, the membrane may be a monolayer membrane where the at least one layer of the membrane has an average pore size less than 0.035 microns (preferably between 0.010 and 0.020 microns), a thickness of 7 microns or less, and the total membrane thickness is 7 microns or less. Alternate membranes may be a bilayer membrane wherein at least one layer of the membranes is a polyolefin tight layer having an average pore size less than 0.035 (preferably between about 0.010 and 0.020 microns) and a thickness of approximately 4 microns, and wherein the total membrane thickness is approximately 8 microns.

[0057] In some of the embodiments described herein, the membrane may be a tri-layer membrane comprising, consisting of, or consisting essentially of: a polypropylene-containing layer as an open layer, a polyethylene-containing layer as a tight layer, and a second polypropylene-containing layer as a second open layer, in that order. In some embodiments described above, the membrane may be a tri-layer membrane comprising, consisting essentially of, or consisting of: a polyethylene-containing layer as an open layer, a polypropylene-containing layer as a tight layer, and a second polyethylene-containing layer as a second open layer, in that order. The polypropylene-containing layer may be a layer that comprises, consists of, or consistsessentially or polypropylene homopolymer, co-polymer, or combination thereof. The poly cthylcnc-containing layer may comprise, consist of, or consist essentially of polyethylene homopolymer, co-polymer, or combination thereof.

[0058] A dry -process membrane, as understood by one of ordinary skill in the art, is a membrane formed without the use of solvents or oils to form pores. In some embodiments, membranes formed by using particulate pore formers may also be excluded from dry-process membranes;, such excluded membranes may include beta- nucleated biaxially oriented polypropylene (BNBOPP) membranes.

[0059] Dry-process membranes have a distinct uniform pore structure recognizable by those skilled in the art. See, for example, Figure 1 or Fig. 1, which shows a uniaxially stretched dryprocess membrane. As can be seen from Fig. 1, dry -process films have elongated or slit-shaped pores. Pores of a biaxially-stretched dry -process membrane may be too large for use in ultrafiltration or nano-filtration applications.

[0060] Generally, a process of preparing a dry-process membrane may include steps that include extruding a thermoplastic polyolefin polymer resin, in the absence of solvent (e.g., while the polymer resin contains less than 5 or 1 percent solvent by weight, e.g., contains at least 95 or 99 percent polymer by weight) to form a non-porous precursor, followed by stretching the precursor in a manner that will cause pores to form. Membranes as described can be prepared by stretching the precursor in a single direction, e.g., uniaxially, and not biaxially, to form pores that are uniaxially oriented and that have an aspect ratio (length dimensiomwidth dimension) of greater than 1.0, e.g., of at least 1.2, 1.5, 2.0, or 3.0.

[0061] Referring to Figure 2, illustrated is a two-layer membrane having a single tight layer and a single open layer. As illustrated, membrane 120 includes open layer 122 and tight layer 124. Tight layer 124 comprises, consists of, or consists essentially of polypropylene, which may be polypropylene homopolymer or polypropylene co-polymer. Open layer 122 comprises, consists of, or consists essentially of polyethylene, which may be polyethylene homopolymer or polyethylene co-polymer. Alternately, tight layer 124 may comprise, consist of, or consist essentially of polyethylene, which may be polyethylene homopolymer or polyethylene copolymer, and open layer 122 may comprise, consist of, or consist essentially of polypropylene, which may be polypropylene homopolymer or polypropylene co-polymer. The tight layer 124 may have a thickness that is not greater than 14 microns and an average pore size of not greaterthan 0.035 microns with pores being uniaxially-oriented and having an aspect ratio of greater than 1.0, 1.2, 1.5, 2.0, or 3.0. The open layer 122 may have a thickness that is not greater than 19 microns, may have a thickness in a range from 6 microns to 19 microns or a thickness in a range from 5 microns to 18 microns, and an average pore size of at least 0.010 microns, an average pore size in a range from 0.010 microns to 0.20 microns. Membrane 120 may have a total thickness, including both layers, that is less than 20 microns.

[0062] A layer of a membrane or multiple layers of a multi-layer membrane may be coated, treated, or chemically modified in a manner that improves filtering performance, particularly non-sieving performance. For example, a membrane be modified or treated to add chemical species to surface of the pores of the membrane, including at internal pore surfaces, that attract contaminants by an electrostatic or chemical interaction.

[0063] According to certain example methods, chemical species that are effective to improve non-sieving filtering performance may be added to a membrane surface by coating the surface with a coating that contains the chemical species. The coating may be applied to the surface and may optionally be crosslinked after being applied to the surface. As an example, a polymer having ionic groups may be coated onto the membrane and crosslinked on the membrane as described in United States Patent 11,731,085, the entirety of which is incorporated herein by reference. As another example, a polymer having ionic groups may be coated onto the membrane without being crosslinked, as described in United States Patent 11,413,586, the entirety of which is incorporated herein by reference.

[0064] By other methods, the chemical species may be chemically attached to, e.g., grafted onto, the polymer of the membrane. See, e.g., United States Patent 10892620, the entirety of which is incorporated herein by reference.

[0065] Referring to Figure 3, illustrated is a three-layer membrane having a single tight layer and a two open layers, one open layer on each side of the tight layer. As illustrated, membrane 130 includes, in order: open layer 132, tight layer 134 and open layer 136. Tight layer 134 comprises, consists of, or consists essentially of polypropylene, which may be polypropylene homopolymer or polypropylene co-polymer. Each of open layers 132 and 136 independently comprise, consist of, or consist essentially of polyethylene, which may be polyethylene homopolymer or polyethylene co-polymer. Alternately, tight layer 134 may comprise, consist of, or consist essentially of polyethylene, which may be polyethylene homopolymer orpolyethylene co-polymer, and each of open layers 132 and 136 may independently comprise, consist of, or consist essentially of polypropylene, which may be polypropylene homopolymcr or polypropylene co-polymer. The tight layer 134 may have a thickness that is not greater than 14 microns, and an average pore size that is not greater than 0.035 microns with pores being uniaxially-oriented and having an aspect ratio of greater than 1.0, 1.2, 1.5, 2.0, or 3.0. Each of the open layers 140 and 160 may independently have a thickness in a range from 3 microns to 9.5 microns, or a thickness in a range from 2 microns to 8.5 microns, and an average pore size of at least 0.010 microns, an average pore size in a range from 0.010 microns to 0.20 microns. Membrane 130 may have a total thickness, including all three layers, that is less than 20 microns.

[0066] In some embodiments described hereinabove, shrinkage of the membrane at 90°C for 1 hour is less than 25%, less than, less than 20%, less than 15%, less than 10%, or less than 5%, less than 4%, less than 3%, less than 2%, or less than 1%. Low shrinkage is indicative of high dimensional stability, which is crucial. Shrinkage of the membrane in filtering application or during assembly of a filter may cause the membrane to rip, tear or modify other properties such that performance is no longer sufficient and / or predictable. Shrinkage is measured by measuring the membrane (LI), placing the membrane in a 90°C oven for one hour unrestrained, measuring the membrane after being in the oven (L2), and calculating shrinkage using the following formula 1. 100 (1)v 7

[0067] A membrane as described may be characterized (in addition to having an open layer and a tight layer as described) by features that include porosity, bubble point, flow time, and retention.

[0068] A membrane may be characterized by bubble point, which can be correlated to pore size of the membrane or of a layer of the membrane, e.g., (mean bubble point) which is an understood property of a porous filter membrane. Bubble point corresponds to pore size, which may correspond to filtering performance, e.g., as measured by retention. A smaller pore size can correlate to a higher bubble point and often to better filtering performance (higher retention). Normally, however, a higher bubble point also correlates to relatively higher resistance of flow through a porous material and a higher flow time (higher resistance to flow and a lower rate of flow for a given pressure drop). Example filter membranes of the present description can exhibit a combination of a relatively higher bubble point, good filtering performance, and a useful levelof flow, e.g., a flow rate or “flow time” that allows for the filter membrane to be used in a commercial filtering process.

[0069] By one method of determining the bubble point of a porous material, a sample of the porous material is immersed in and wetted with a liquid having a known surface tension, and a gas pressure is applied to one side of the sample. The gas pressure is gradually increased. For purposes of this description, unless otherwise noted, the measure bubble point is what is referred to as a “mean bubble point,” as opposed to an “initial bubble point.” A mean bubble point is measured as mean pressure of gas between an initial bubble point and a condition of a dry membrane. Initial bubble point is a pressure at which a first bubble passes through the membrane. These terms are well known in the porous membrane arts.

[0070] Examples of useful bubble points of a porous filter membrane as described, measured using a test method described in the Examples, herein below, can be at least 50, 80, 90, 100, or 120 pounds per square inch (psi) or greater, e.g., up to 200 or 300 pounds per square inch, while the membrane also exhibits useful properties of flow time and retention as described elsewhere herein (measured using HFE-7200 (3M), at a temperature of 22 degrees Celsius).

[0071] In combination with a desired bubble point and filtering performance, a membrane as described can exhibit a useful, effective level of a resistance to flow of liquid through the membrane. A resistance to flow of liquid through the membrane can be measured in terms of flow rate or flow time (which is inverse to flow rate). A membrane as described can preferably have a useful or a relatively low flow time, preferably in combination with a bubble point that is relatively high, and good filtering performance.

[0072] Flow time of a membrane may be measured by various different techniques and using various fluids, including isopropyl alcohol. Example membranes may have a flow time measured using IPA that is at or above 400 seconds, e.g., in the range of from about 400 seconds to about 40,000 seconds, 500 seconds to about 40,000 seconds, 600 seconds to about 40,000 seconds, 700 seconds to about 40,000 seconds, 800 seconds to about 40,000 seconds, 900 seconds to about 40,000 seconds, 1,000 seconds to about 40,000 seconds, 2,000 seconds to about 40,000 seconds, 3,000 seconds to about 40,000 seconds, 4,000 seconds to about 40,000 seconds, 5,000 seconds to about 40,000 seconds, 6,000 seconds to about 40,000 seconds, 7,000 seconds to about 40,000 seconds, 8,000 seconds to about 40,000 seconds, 9,000 seconds to about 40,000 seconds, 10,000 seconds to about 40,000 seconds, in the range from about 11,000 seconds toabout 40,000 seconds, 17,000 seconds to about 40,000 seconds, 20,000 seconds to about 40,000 seconds, 25,000 seconds to about 40,000 seconds, 30,000 seconds to about 40,000 seconds, or 35,000 seconds to about 40,000 seconds. Flow time may be flow time using IPA (isopropyl alcohol), wherein the flow time is the time to flow 500 ml of isopropyl alcohol (IPA) at a temperature of 21°C and a pressure of 0.1 MPa through a 47 mm disc of the membrane having an area of 12.5 cm2.

[0073] A level of effectiveness of a filter membrane for removing unwanted material (i.e., “contaminants”) from a liquid can be measured, in one fashion, as “retention.” Retention, with reference to the effectiveness of a filter membrane (e.g., a filter membrane as described), generally refers to a total amount of an impurity (actual or during a performance test) that is removed from a liquid that contains the impurity, relative to the total amount of the impurity that was in the liquid before passing the liquid through the filter membrane. The “retention” value of a filter membrane is, thus, a percentage, with a filter that has a higher retention value (a higher percentage) being relatively more effective in removing particles from a liquid, and a filter that has a lower retention value (a lower percentage) being relatively less effective in removing particles from a liquid. Membranes prepared according to example methods of the present description can exhibit filtering performance as measured by retention that is at least comparable to commercial filter membranes that are prepared from comparable materials (e.g., polyolefins), that have comparable, nearly comparable, or somewhat similar thickness, and flow properties (as measured by flow time) and bubble points that are within comparable ranges. For example, disclosed membranes and disclosed filter products comprising the membranes may have a retention value (e.g., as measured by G25 1% monolayer particle loading) of no less than 20%, no less than 25%, no less than 30%, no less than 35%, no less than 40%, no less than 45%, no less than 50%, no less than 55%, no less than 60%, no less than 65%, no less than 70%, no less than 75%, no less than 80%, no less than 85%, no less than 90%, no less than 95%, or no less than 99%.

[0074] In certain examples, membranes of the present description can exhibit a useful or improved combination of bubble point (mean bubble point) and flow properties of a liquid through the membrane (e.g., as measured in terms of flow time). Compared to comparable microporous polyolefin filter membranes, useful or preferred membranes of the present description can have a highly desirable combination of increased bubble point, for a similar flowtime. Over a range of bubble points relative to flow time, example membranes may exhibit a higher bubble point for an equal flow time, or, alternately stated, a reduced (improved) flow time at an identical bubble point. Example membranes can exhibit flow time and bubble point properties such as the following: a flow time below 2000 seconds and a mean bubble point of 75 psi or greater a flow time below 3000 seconds and a mean bubble point of 100 psi or greater; a flow time below 5000 seconds and a mean bubble point of 125 psi or greater; or a flow time below 8000 seconds and a mean bubble point of 150 psi or greater; wherein: flow time is defined herein, and bubble point is a mean bubble point measured using HFE-7200 liquid fluid at room temperature. These membranes also exhibit useful levels of filtering measured in terms of “retention,” e.g., filtering performance that is in a range comparable to other polyolefin filter membranes of comparable thickness.

[0075] According to another preferred measure, example membranes as described can exhibit flow time and bubble point properties such as: a flow time below 1500 seconds and a mean bubble point of 75 psi or greater; a flow time below 2500 seconds at a mean bubble point of 100 psi or greater; a flow time below 4000 seconds at a mean bubble point of 125 psi or greater; a flow time below 6000 seconds at a mean bubble point of 150 psi or greater; and a flow time below 8000 seconds at a mean bubble point of 175 psi or greater. These membranes also exhibit useful levels of filtering measured in terms of “retention,” e.g., filtering performance that is in a range comparable to other polyethylene filters of comparable thickness.

[0076] The filter membrane can be contained within a larger filter product such as a filter housing or filter cartridge, which includes any structure that supports the membrane to allow a liquid fluid to flow through the membrane from an inlet side of the membrane, through the membrane, to exit an outlet side of the membrane. The housing includes an inlet on one side of the supported membrane that allows fluid to enter the housing on an upstream side of the membrane when the membrane is supported by the housing, and an outlet on a second side of the membrane that allows fluid that passes through the membrane, while the membrane is supported by the housing, to exit the membrane on a downstream side of the membrane. The terms “inlet” and “outlet” may refer to a specific structure such as defined opening or a defined conduit (tube, pipe, or engagement thereof) of a housing or a component of a housing (e.g., a supportive frame, a core, a cage, or the like), or may refer to a space (an “inlet space” or an “outlet space”) located on either side of the membrane, upstream and downstream of the membrane, respectively, whenthe membrane is supported by the housing that accommodates flow of fluid into and out of the housing and through the membrane. The terms “inlet” and “outlet” may also refer more generally to spaces on either side of the membrane that together accommodate the flow of fluid into the membrane on an upstream or inlet side of the membrane, then through the membrane, and from the membrane on an outlet side or a downstream side of the membrane.

[0077] The housing includes the membrane supported within a larger filtering system to allow a flow of fluid through the membrane within the housing, particularly a filtering system that supplies filtered liquid chemical to a tool or process for manufacturing microelectronics or semiconductor devices. The filtering system will place the filter membrane, e.g., as part of a filter, filter housing, or filter cartridge, in a flow path of a liquid chemical to cause the liquid chemical to flow through the filter membrane so that the filter membrane is able to remove impurities or contaminants from the liquid chemical. The filter product or housing may include one or more of various additional materials and structures that support the filter membrane within the filter to cause fluid to flow from a filter inlet, through the filter membrane, and thorough a filter outlet, thereby passing through the filter membrane when passing through the filter product. The filter membrane supported by the filter structure can be in any useful shape, e.g., a pleated cylinder, cylindrical pads, one or more non-pleated (flat) cylindrical sheets, a pleated sheet, among others.

[0078] One example of a filter structure (e.g., housing) that includes a filter membrane in the form of a pleated cylinder can be prepared to include the following component parts, any of which may be included in a filter product but may not be required: a rigid or semi-rigid core that supports a pleated cylindrical coated filter membrane at an interior side (inlet or outlet) of the pleated cylindrical filter membrane; a rigid or semi-rigid cage that supports or surrounds an exterior side (outlet or inlet) of the pleated cylindrical filter membrane at an exterior of the filter membrane; optional end pieces or “pucks” that are situated at each of the two opposed ends of the pleated cylindrical filter membrane. Regarding a housing in the form of a cartridge, the cartridge is considered to have an inlet on one side of the filter membrane and an outlet on an opposite side of the filter membrane; an inlet or an outlet may be on either side of the membrane depending on the direction of flow of fluid through the membrane.

[0079] A filter housing can also include an inlet, an outlet, or both in the form of a conduit, pipe, tube, or other fluid flow channel adapted to connect through one or more appurtenant fluidconduits to receive a liquid fluid from a fluid supply at a first side of the filter membrane (an inlet side), to cause the fluid to flow through the membrane within the housing, and to cause the fluid to flow from a second side of the filter membrane (an outlet side) then through the outlet to a fluid destination that may be a tool for processing semiconductor or microelectronic devices . The filter housing can be of any useful and desired size, shape, and materials, and can preferably be made of suitable polymeric materials.

[0080] As one example, Figure 4 shows filter product (replaceable filter cartridge) 230, which is a product of pleated cylindrical component 210 and end piece 222, with other optional components. Cylindrical component 210 includes a filter membrane 212 as described herein, and is pleated. End piece 222 is attached (e.g., “potted”) to one end of cylindrical filter component 210. End piece 222 can preferably be made of a melt-processable polymeric material. A core (not shown) can be placed at the interior opening or space “inlet” 224 of pleated cylindrical component 210, and a cage (not shown) can be placed about the exterior opening or space (“outlet”) of pleated cylindrical component 210. The cartridge includes an inlet and an outlet (e.g., at a core, cage, or other supporting structure) on each of the inlet (upstream) side of the membrane and the outlet (downstream) side of the membrane, with the location of the inlet and the outlet depending on the direction in which fluid is caused to flow through the fluid membrane while cartridge 230 is installed within a housing, which can also have an inlet and an outlet. A second end piece (not shown) can be attached (“potted”) to the second end of pleated cylindrical component 210. The resultant pleated cylindrical filter membrane included in a replaceable filter cartridge 230 with two opposed potted ends and optional core and cage can then be placed into a larger (secondary) filter housing that includes an upstream housing inlet to receive fluid into the filter membrane, and a downstream housing outlet to discharge fluid that has passed through the filter membrane, and that is configured so that an amount of fluid that enters the housing at the housing inlet must necessarily pass through filtration membrane 212 before exiting the filter housing at the housing outlet.

[0081] Referring to Figure 5, example filter product 250 includes a housing that contains replaceable filter cartridge 230 within an interior. Filter product 250 includes a two-component housing that includes bowl 252 attached to base 254 at an open end of bowl 252. Optionally, bowl may be removably engaged with base 254 to allow bowl 252 to be separated from base 254 to allow a removable filter cartridge 230 to be placed into or removed from the interior of thehousing. The assembled housing includes inlet 256, inlet space 260 at an interior side of cartridge 230, outlet space 262 between cartridge 230 and bowl 252, and outlet 258. Removable filter cartridge 230 can be located at an interior of bowl 252 in an arrangement to allow liquid to flow into inlet 256, into inlet space 260, then through filter assembly 212 of cartridge 230, into outlet space 262, then to be discharged from filter product 250 through outlet 258.

[0082] A filter housing or related components (e.g., gaskets, fittings) can be of any useful and desired size, shape, and materials. Example housings and components may be made from fluorinated or non-fluorinated polymers such as nylon, polyethylene, or fluorinated polymer such as a polytetrafluoroethylene- co-perfluoro(alkyvinylether)), TEFLON® perfluoroalkoxyalkane (PFA), perfluoromethylalkoxy (MFA), or another suitable fluoropolymer (e.g., peril uoropol y mcr) .

[0083] A membrane assembly as described or a filter or filter component that contains a membrane assembly can be useful in a method of filtering a liquid chemical to purify or remove unwanted materials (contaminants) from the liquid chemical, especially to produce a highly pure liquid chemical that is useful for an industrial process that requires a liquid chemical input that has a very high level of purity. Generally, the liquid chemical may be any of various useful commercial liquid chemicals of a type that is useful in any industrial or commercial application. Particular examples of membrane assemblies and filter products as described can be used for purifying a liquid chemical that is used in a semiconductor or microelectronic fabrication application, e.g., for filtering a liquid solvent or other process solution used in a method of semiconductor photolithography, a wet etching or cleaning step, a method of forming spin-on- glass (SOG) for a backside anti-reflective coating (BARC) method, etc.

[0084] Some specific, non-limiting, examples of solvents (including cleaning solutions) that can be filtered using a membrane assembly as described include: n-butyl acetate (nBA), isopropyl alcohol (IPA), 2-ethoxyethyl acetate (2EEA), a xylene, cyclohexanone, ethyl lactate, methyl isobutyl carbinol (MIBC), methyl isobutyl ketone (MIBK), isoamyl acetate, undecane, propylene glycol methyl ether (PGME), propylene glycol monomethyl ether acetate (PGMEA), or a mixture of any of these, such as mixture of PGME and PGMEA; or concentrated or dilute ammonium hydroxide, hydrogen peroxide, hydrochloric acid, HF, sulfuric acid, another peroxide solution, or combinations of these such as a combination of ammonium hydroxide and hydrogen peroxide, or a combination of hydrochloric acid and hydrogen peroxide.EXAMPLES

[0085] Example 1 is a dry-process monolayer polypropylene-containing membrane having a total thickness of 7 microns.

[0086] Example 2 is a dry-process tri-layer membrane comprising three polypropylene- containing layers with a total thickness of 6 microns. The polypropylene-containing layer with the smallest pore size is approximately 2 microns in thickness with a pore size of 22 nm.

[0087] Example 3 is a dry-process membrane with a pore size of 20 nm.

[0088] Comparative Example 1 is a dry-process monolayer polypropylene-containing membrane having a total thickness of 7 microns.

[0089] Comparative Example 2 is a dry-process tri-layer membrane comprising a polypropylene-containing layer, a polyethylene-containing layer, and a polypropylene-containing layer in that order. The total thickness of the membrane is 20 microns, with the PP-containing layer thicknesses adding up to 14 microns. The polypropylene-containing layer has an average pore size of 35 nm.

[0090] Comparative Example 2 has the issue of the pores being too big for nano-filtration or ultra-filtration processes. Comparative Example 1 has a high shrinkage, which makes it unsuitable for use due to low dimensional stability. Shrinkage of the membrane in application or during assembly may cause the membrane to rip, tear or modify other properties such that performance is no longer sufficient and / or predictable. Examples 1 and 2 have high dimensional stability (e.g., low shrinkage), and small enough pores for use in nano-filtration or ultra-filtration processes (including filtration of gas or liquid).

Claims

CLAIMS1. A filter product for processing microelectronics or semiconductor processing fluids, comprising: a housing having an inlet and an outlet, a multi-layer microporous membrane disposed between the inlet and the outlet, the multi-layer microporous membrane comprising: a first polyolefin layer, and a second polyolefin layer comprising mono-axially oriented micropores; wherein the filter product is characterized as having a mean bubble point of at least 50 psi, at least 80 psi, at least 90 psi, at least 100 psi, or at least 120 psi measured using HFE-7200 liquid fluid at room temperature.

2. The filter product of claim 1 characterized as having a mean bubble point of up to 200 psi or up to 300 psi.

3. The filter product of claim 1 or 2, wherein the micropores have an average aspect ratio greater than 1.0, greater than 1.2, greater than 1.5, greater than 2.0, or greater than 3.0.

4. The filter product of any of claims 1 through 3, the multi-layer microporous membrane comprising: the first polyolefin layer, the second polyolefin layer, and a third polyolefin layer; wherein the first polyolefin layer and the third polyolefin layer each comprise polyethylene, and the second polyolefin layer comprises polypropylene.

5. The filter product of any of claims 1 through 3, the multi-layer microporous membrane comprising: the first polyolefin layer, the second polyolefin layer, anda third polyolefin layer; wherein the first polyolefin layer and the third polyolefin layer each comprise polypropylene, and the second polyolefin layer comprises polyethylene.

6. The filter product of any of claims 1 through 4, wherein the second polyolefin layer comprises: at least 90 wt% polypropylene or at least 95 wt% polypropylene based on total weight of the second polyolefin layer; or at least 90 wt% polyethylene or at least 95 wt% polyethylene based on total weight of the second polyolefin layer.

7. The filter product of any of claims 1 through 6, wherein the second polyolefin layer has a thickness less than 14 microns, less than 13 microns, less than 12 microns, less than 11 microns, less than 10 microns, less than 9 microns, less than 8 microns, less than 7 microns, less than 6 microns, less than 5 microns, less than 4 microns, less than 3 microns, less than 2 microns, or less than 1 microns.

8. The filter product of any of claims 1 through 7, wherein the first polyolefin layer comprises at least 60 wt% polyolefin based on total weight of the first polyolefin layer.

9. The filter product of any of claims 1 through 8, wherein the mono-axially oriented micropores of the second polyolefin layer has an average pore size less than 0.035 microns, less than 0.030 microns, less than 0.025 microns, or less than 0.020 microns.

10. The filter product of any of claim 1 through 9, wherein the mono-axially oriented micropores of the second polyolefin layer have an average pore size in a range from about 0.010 microns to about 0.020 microns.

11. The filter product of any of claims 1 through 10, wherein the first polyolefin layer has an average pore size greater than the average pore size of the second polyolefin layer.

12. The filter product of any of claims 1 through 9, having a total thickness of not greater than 14 microns, not greater than 13 microns, not greater than 12 microns, not greater than 11 microns, not greater than 10 microns, not greater than 9 microns, not greater than 8 microns, not greater than 7 microns, not greater than 6 microns, not greater than 5 microns, not greater than 4 microns, not greater than 3 microns, not greater than 2 microns, or not greater than 1 microns.

13. The filter product of any of claims 1 through 10, exhibiting a measured flow time in a range from 400 seconds to 40,000 seconds, measured using isopropyl alcohol, wherein the flow time is the time to flow 500 ml of isopropyl alcohol at a temperature of 21° Celsius and a pressure of 0.1 MPa through a 47 mm disc of the membrane having an area of 12.5 cm2.

14. The filter product of any of claims 1 through 13 characterized in having a retention no less than 20%, no less than 25%, no less than 30%, no less than 35%, no less than 40%, no less than 45%, no less than 50%, no less than 55%, no less than 60%, no less than 65%, no less than 70%, no less than 75%, no less than 80%, no less than 85%, no less than 90%, no less than 95%, or no less than 99%.

15. The filter product of any of claims 1 through 14, wherein the multi-layer microporous membrane is a flat sheet, is wound, or is pleated.

16. The filter product of any of claims 1 through 15, wherein the multi-layer microporous membrane is a pleated cylinder.

17. The filter product of any of claims 1 through 16, comprising: the housing surrounding the membrane, a housing inlet that allows fluid to flow into the housing and into the inlet space, and a housing outlet that allows the fluid to flow out of the housing after the fluid passes through the membrane.

18. The filter product of any of claims 1 through 17 comprising a frame and the multi-layer microporous membrane supported by the frame with an inlet on one side of the filter membrane and an outlet on a second side of the membrane.

19. The filter product of any of claims 1 through 18, wherein the filter product is a replaceable filter cartridge.

20. The filter product of any of claims 1 through 19, wherein the multi-layer microporous membrane is modified by at least one of coating, washing, extracting, forming, shaping, folding, winding, pleating, and forming into a pleated cylinder.

21. A method of using the filter product of any of claims 1 through 20, the method comprising passing a fluid through the filtration membrane.

22. The method of claim 21, wherein the fluid comprises n-butyl acetate (nBA), isopropyl alcohol (IPA), 2-ethoxy ethyl acetate (2EEA), a xylene, cyclohexanone, ethyl lactate, methyl isobutyl carbinol (MIBC), methyl isobutyl ketone (MIBK), isoamyl acetate, propylene glycol methyl ether (PGME, or (2-methoxy-l -methylethylacetate)), propylene glycol monomethyl ether acetate (PGMEA), propylene glycol ethyl ether (PGEE), NMP (l-methyl-2-pyrrolidone), gamma-butyl lactone, dimethyl ether, dibutyl ether, toluene, concentrated ammonium hydroxide, dilute ammonium hydroxide, hydrogen peroxide, another peroxide solution, hydrochloric acid, hydrofluoric acid, sulfuric acid, or any mixture thereof.

23. The method of claim 21 or 22, wherein after passing through the filtration membrane, the fluid is characterized as comprising a reduced amount of a contaminant relative to before passing through the filtration membrane.

24. The method of claim 23, wherein the contaminant is reduced by no less than 20%, no less than 25%, no less than 30%, no less than 35%, no less than 40%, no less than 45%, no less than 50%, no less than 55%, no less than 60%, no less than 65%, no less than 70%, no less than 75%, no less than 80%, no less than 85%, no less than 90%, no less than 95%, or no less than 99%.

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