Brush pad and method of manufacture

Abstract

A brush pad for semiconductor wafer cleaning comprising a microporous core configured to be fluidly coupled to a DIW supply and a cover made of fabric comprising a base made of woven fabric, knitted fabric, or non-woven fabric, and at least two types of free standing fibers or fiber loops arranged in a pattern of nodules, each type of the free standing fibers or fiber loops made of a different material designed to have different cleaning activity or affinity for different types of impurities.

Description

Brush pad and method of manufactureCROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority from US provisional patent application serial number 63 / 613,080 filed on December 21, 2023 with the US Patent Office and which is incorporated herein in its entirety for all purposes.BACKGROUND

[0002] Various exemplary embodiments of the present invention relate generally to wafer cleaning and, more particularly, to an engineered brush pad for reduced DIW (Deionized water) usage.

[0003] Semiconductor fabrication processes require significant water use.Currently, each advanced node, completed 200 mm equivalent wafer uses approximately 1300 gallons of water. See “Intel Corporate Responsibility Report 2020-21.” Based on the total worldwide semiconductor capacity of approximately 135 million wafers (200 mm equivalent) the water usage is approximately 175 billion gallons of water per year. See https: / / www.eenewseurope.com / news / top-five-chip-makers-dominate-global -wafer- capacity.

[0004] As semiconductor usage continues to grow, water usage in semiconductor fabrication will cause strain on total available natural water resources and its availability for other purposes. Overall water usage needs to be reduced for efficient resource utilization in alignment with current Global 1.5 °C climate goals.

[0005] One important element to reducing water usage is to address the water usage at the source by designing more efficient processes. Chemical MechanicalPolishing (CMP) process is one of the key processes in semiconductor wafer processing and is water intensive. A leading chip using a lOnm process may need to revisit dielectric and metal CMP steps in total for more than 20 times for fabricating the device. Wafers are polished by pressing against a polyurethane pad while applying a slurry composed of metal oxide nanoparticles along with chemicals to affect removal with smooth finish. Wafers are then cleaned in a stand-alone or integrated Post CMP (PCMP) cleaner using PVA brushes which have water flowing through the brushes. See “Process Consistency in Post-CMP Cleaning: Challenges and Opportunities” Singh, Rakesh K, et. al.

[0006] Additionally, water and cleaning chemicals are sprayed onto the wafers to aid removal of particles and debris. Existing brushes are highly porous network of crosslinked polyvinyl acetate with pore size in the range of 30 - 100 pm depending on the manufacturer and the type of brush being used. Porosity may range from 80-90%. Cleaning is accomplished by pressing a rotating, water filled, brush against a rotating wafer.

[0007] A typical PCMP cleaner for 300 mm wafers has two brush stations with each station containing two brushes. The wafer is cleaned by placing it between the two brushes. The water flow rate through each brush is approximately 0.5 liters per minute, so the PCMP cleaner requires continuous 2 liters per minute, while additional spray nozzles are on during wafer cleaning. Spray nozzles use additional water, up to 2 liters per minute. The PCMP cleaner therefore uses 2 liters per minute continuous and up to 4 liters per minute during wafer cleaning. This translates to up to 1 million liters per cleaner per year (280K gallons) in standby mode or 2 million liters / year (560k gallons) in 100% cleaning mode. A more DIW efficient process or cleaner is therefore very desirable.

[0008] In existing brush designs, a microporous PVAc (polyvinyl acetate) brush is used. Water flow rate required to get uniform flow through the brush is a function of the pore percentage and the pore size. Higher pore percentage generally requires higher flow. Also, larger pore size generally requires higher flow. Similarly brush compressibility is also proportional to pore size and pore percentage. Current brush design, therefore, has strong coupling between pore percentage, pore size and compressibility to affect wafer surface cleaning. Reduction in pore percentage can help reduce water flow but also reduces compressibility affecting cleaning efficiency.Additionally for conventional brush cleaning surface contact is also controlled by pores. DIW flow through the brush and DIW sprayed onto the brush-wafer during cleaning need to be optimized for cleaning. In conventional designs, the DIW flow through the brush needs to be adequate or sufficiently large to eliminate the risk of back diffusion of debris into the brush. This is an important consideration which leads in high DIW usage.

[0009] FIG. 1(a) is a simplified schematic of a conventional cylindrical brush and Fig 1(b) shows the cross section of the same. The brush has a PVA brush core 101 A, 10 IB with an internal surface 101 A mounted on a mandrel 103 through which DIW flows to and through the brush. Brush nodules 102 are spaced out on the outer surface 10 IB of the cylindrical brush and contact the wafer during cleaning. Additional DIW 104 is sprayed onto the brush during cleaning. In FIG. IB Rl, R2, and R3 represent the flow resistances in an inner and outer regions of the cylindrical brush, and within the nodules 102.

[0010] U.S. Pat. No. 4,098,728, describes a polyvinyl acetal sponnd a method for making the same. In this method, pore spaces in the sponge are formed by gas bubbles; rather than pore forming chemical additives such as starch / sulfate combinations.Because the sponge disclosed in this patent does not have any starch residue, it has been particularly useful in medical applications in which starch residues can cause a foreign body reaction when in contact with human tissue.

[0011] The use of synthetic sponges, made of polyvinyl acetal or cleaning devices is well known. For example, U.S. Pat. No. 4,566,911 discloses a roller scrubbing device using a polyvinyl acetal material for cleaning semiconductor chips having a surface layer of elastic polyvinyl acetal material with an average pore diameter ranging from 10 to 200 microns. If the average pore opening is less than 10 pm, the porous elastic material may have poor elasticity, thus making the performance of the cleaning roll unsatisfactory. If the average pore opening is more than 200 pm, the porous elastic material becomes unsuitable for the cleaning roll because of the bastard pore configuration. If the 30% compression stress is less than 15 g / cm2, the porous elastic material is too soft, thus developing strain by the rotation of the cleaning roll. If the 30% compression stress is more than 150 g / cm2, the porous elastic material is too rigid, resulting in poor elasticity.

[0012] U.S. Pat. No. 6,080,092 describes an industrial sponge roller device with a cylindrical body of polyvinyl acetal material and a plurality of projections of a truncated conical shape extending from an outer surface of the cylindrical body. Conventional synthetic sponges have a polymer structure with "dead end pockets" formed therein that trap residue and trace amounts of metals and have non-uniform pore sizes causing fluid backup and residue deposit. As the sponge wears, these metals can come out of the sponge in the form of particulate matter. Such particulate matter can damage the surfaces that are to be cleaned. Further, this type of sponge has tiny fibrils in the pores thereof that are a result of spaces between the pore forming chemical additive during a cross-linkingreaction. "Cross-linking" refers to the formation of ester bonding between chains of the two adjacent hydroxyl groups that occur with the reaction of polyvinyl alcohol and aldehyde. This reaction hardens and strengthens the resulting material.

[0013] These conventional brushes may have material and structural inhomogeneity that is inherent to the manufacturing process. Non uniformity of material and pore structure creates non uniform contact between the brush and wafer, which translates to nonuniform contact force of cleaning. Additionally, total contact density of a flat surface is inherently limited. Typical PVA brushes have 4-10 mm diameter nodules on their surface, which perform the actual cleaning. The contact area therefore reduces even further. It would be highly advantageous, therefore, to remedy the foregoing and other deficiencies inherent in the prior art.SUMMARY OF THE INVENTION

[0014] In view of the above, there is provided a new brush pad design with new structure, surface features, and profile. The brush pad can be used instead of the traditional brushes for cleaning a wafer in existing cleaning apparatuses.

[0015] According to an embodiment of the present invention there is provided a composite brush pad for semiconductor wafer cleaning. Accordingly, the brush pad comprises: a microporous core having an inner surface and an outer surface; and a cover securely positioned on the outer surface of the core, wherein the inner surface of the core is configured to removably connect onto a mandrel of a brush pad,wherein the cover comprises a woven or knitted fabric with a plurality of freestanding fibers and / or fiber loops extending above the outer surface of the cover.

[0016] The cover may comprise freestanding fibers and / or fiber loops extending in a direction forming an angle with the outer surface of the core of at least 45 degrees.

[0017] The freestanding fibers and or the fiber loops may extend in a direction normal or substantially normal to the brush pad surface.

[0018] The freestanding fibers and or the fiber loops may extend in a direction forming an angle with the outer surface of the core of from 20 to 40 degrees.

[0019] The microporous core may be made of a microporous plastic material or composite plastic material comprising micro-channels and / or open pores allowing cleaning fluid (e.g., water and / or any cleaning chemicals) to flow from the inner surface of the core through the core and out of the outer surface of the core into the cover.

[0020] The freestanding fibers and / or fiber loops may be 1 micron to 200 micron in diameter, preferably 1 to 100 microns in diameter, and more preferably 1 to 10 microns in diameter and extend 0.5 mm to 10 mm in height above the outer surface, preferably 1.0 mm to 7 mm in height above the outer surface of the cover, and more preferably 2.0 mm to 5.0 mm in height above the outer surface of the cover.

[0021] The fibers may be made of a single polymer or combination of polymers comprising polyolefin, polyester, nylon, polyurethanes, , polyvinyl acetate (PVAc), or engineered fibers such as poly-para-phenylene terephthalamide (known as KEVLAR) , aromatic polyamides, polytetrafluoroethylene (PTFE), and ultra-high molecular weight polyethylene, preferably, polyolefin (e.g., polypropylene, or polyethylene), polyester2e.g., polyethylene terephthalate, polybutylene terephthalate), and polyamides (e.g., nylon).

[0022] The fiber density of the base of the cover may be 20 yams (X+Y) per cm2to 200 yarns (X+Y) per cm2, preferably 30 per cm2to 180 yams (X+Y) per cm2, more preferably 40 per cm2to 150 yarns per cm2.

[0023] The freestanding loop density is 100 per cm2to 1200 fiber loops per cm2, preferably 150 per cm2to 1000 per cm2, and more preferably 150 per cm2to 600 loops per cm2.

[0024] The cover surface may comprise both single freestanding fibers and fiber loops.

[0025] The cover surface may comprise fiber loops only.

[0026] Loops may be arranged in a pattern including linear, circumferential, spiral, arc, nodular, or some other geometric pattern, preferably linear, nodular, or spiral, and more preferably nodular or spiral.

[0027] In an embodiment, the freestanding fibers and / or loops may be formed together with the base of the cover on the surface of the cover in a single weaving or knitting process.

[0028] In another embodiment, the freestanding fibers and / or loops may be formed after the base of the cover is formed by tufting the fibers through the base of the cover, he core may be made of open cell microporous polymer material such as, for example, PVA, polyolefins such as polypropylene, polyurethane, preferably polypropylene and PVA.

[0029] The core may be made of a melt-blown polypropylene filter cartridge.

[0030] The core may be made of melt-blown nonwoven fibers made of a polyolefin, nylon, polyester, polyvinyl acetate, or urethane.

[0031] In an embodiment, the cover may have the form of a sleeve positioned around the core. The sleeve may have a cylindrical, disc, or prismatic shape.

[0032] In an embodiment the brush pad for post chemical / mechanical polishing cleaning of a semiconductor wafer may comprise: a composite microporous core with open cell pores allowing water to pass through it; and an outer cover disposed on the outer surface of the microporous core, the outer cover comprising a fabric made base and fiber loops on the fabric base and extending above the top surface of the cover, wherein at least two different types of fibers are used to make the fiber loops.

[0033] The cover weave density may be higher than a core brush pad density.

[0034] The core may have a pore percentage from 60% to 90 %, or 70% to 90% and the cover base may have a pore percentage of from 40% to 70 %, or 50% to 70%.

[0035] In an embodiment, a brush pad for semiconductor wafer cleaning is provided, the brush pad comprising:

[0036] a microporous core having a disc or prismatic shape with a first surface of the brush pad being configured to be fluidly coupled to a DIW supply, and a network of pores fluidly connecting the first surface to the second surface wherein in operation DIW flows in the microporous core through the first surface and through the network of pores reaches the second surface;

[0037] a cover comprising a base made of woven fabric, knitted fabric, or nonwoven fabric, and at least two types of free standing fibers or fiber loops arranged in apattern of nodules, each type of the free standing fibers or fiber loops made of a different material designed to have different cleaning activity or affinity for different types of impurities.

[0038] In an embodiment, a first type of freestanding fibers and or fiber loops are with nylon, polyester, or a combination thereof and a second type of fibers and or fiber loops are made with polyester, PVA, or a combination thereof.

[0039] In an embodiment, the cover may be securely attached to the core via hot melt adhesive.

[0040] These and other features and advantages of the invention will become apparent to those skilled in the art upon a review of the description of the presently preferred embodiments of the invention, viewed in conjunction with the appended drawings.BRIEF DESCRIPTION OF THE DRAWINGS

[0041] FIGS. 1(A) and 1(B) are simplified schematics of a conventional brush for wafer cleaning.

[0042] FIG. 2 (A) is a simplified schematic of a brush pad for wafer cleaning according to an embodiment of the present invention.

[0043] Fig 2(B) shows cross section of the brush pad of FIG. 2A.

[0044] FIG. 2 (C) is a simplified schematic of a brush pad for wafer cleaning according to an embodiment of the present invention.

[0045] Figure 3 shows a simplified enlarged view of a close-up of a fiber loop acting upon a particle defect on the surface of a wafer.

[0046] Figure 4 shows a top view of a conventional PVA brush pad with a plurality of nodules on its top surface.

[0047] Figure 5 shows a top view of the cover of the brush pad according to an embodiment of the present invention showing a nodular pattern formed by the fiber loops on the cover surface.DETAILED DESCRIPTION OF THE INVENTION

[0048] Various embodiments of the present invention are described below in more detail with reference to the accompanying drawings. We note, however, that the present invention may be embodied in different other embodiments, forms, and variations thereof and should not be construed as being limited to the embodiments set forth herein. Rather, the described embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the various aspects and features of the present invention to those skilled in the art to which this invention pertains. Throughout the disclosure, like reference numerals refer to like parts throughout the various figures and embodiments of the present invention.

[0049] The drawings are not necessarily to scale and, in some instances, proportions may have been exaggerated to clearly illustrate features of the embodiments.

[0050] It will be further understood that when an element is referred to as being "connected to", or "coupled to" another element, it may be directly on, connected to, or coupled to the other element, or one or more intervening elements may be present. In addition, it will also be understood that when an element is referred to as being "between" two elements, it may be the only element between the two elements, or one or more intervening elements may also be present.

[0051] It will be further understood that the terms "comprises," "comprising," "includes," and "including" when used in this specification, specify the presence of the stated elements, and do not preclude the presence or addition of one or more otherelements.

[0052] It is also noted, that in some instances, as would be apparent to those skilled in the relevant art, a feature or element described in connection with one embodiment may be used singly or in combination with other features or elements of another embodiment, unless otherwise specifically indicated.

[0053] Hereinafter, the various embodiments of the present invention will be described in detail with reference to the attached drawings.

[0054] According to a first embodiment of the present invention, a brush pad comprises a microporous core having an inner and an outer surface. The inner surface of the microporous core may be attached to a mandrel which itself attaches to a cleaner device feeding deionized water into the brush pad through the mandrel. The inner surface of the microporous core may be configured to fluidly couple with the mandrel. The inner surface of the microporous core may be configured to readily mount securely onto the mandrel. Various well-known designs may be used. The outer surface of the microporous core is attached to a cover containing a base made of fabric and freestanding fibers and or fiber loops protruding from the base. Preferably, at least two different materials are used to make the freestanding fibers and or the fiber loops. In an embodiment, the cover may comprise adjacent loops which are made of different materials. In an embodiment, each of the loops may comprise two different fibers each made from a different material. For example, at least two different fibers may be combined into a single composite yarn and the single composite yarn may be used to form the free standing fibers and or the loops on the outer surface of the cover.

[0055] The cover may be securely attached to the microporous core by any suitable means including, for example, sonic welding, thermal welding, stitching, hotmeltadhesive or other means that provide a secured connection. In an embodiment the cover may be connected to the core in a removable manner, for example, using one or more removable connectors, thus, allowing easy replacement of the cover after it has been used with a new cover. In yet another preferred embodiment, the cover is attached to the core via an adhesive. The adhesive may be a hotmelt adhesive. Examples of hotmelt adhesives include thermoplastic polymers such as ethylene-vinyl acetate (EVA), polyolefins, or polyurethane. The hot melt adhesive may be applied using a hot glue gun in a melt state. The hot melt adhesive may be placed within a limited area of the inside surface of the cover, away from loops, so that it may not significantly reduce the fluid flow. Once the hotmelt adhesive cools down it sets quickly and forms a strong bond between the cover and the core.

[0056] According to an embodiment, the cover with the freestanding fibers and or the fiber loops may be formed using a weaving or knitting process for highly controlled height and spatial arrangement of the freestanding fibers and or the fiber loops. In an embodiment several fibers of different materials may be combined to make the fiber or yam used in the knitting or weaving of the fabric base and of the freestanding fibers and or of the fiber loops of the cover. The cover may comprise a porous base. The porous base may be made, for example, of the same material as the fiber loops and preferably using the same weaving or knitting process. Unless specifically mentioned, yam and fiber are used interchangeably without changing the meaning of the invention. Traditional weaving process involves creating a fabric by interlacing fibers or yam in an X-Y orientation. Several, long monofilament fibers or short length fibers may be processed to make the yam for the weaving or knitting process. Individual fiber diameter and number of fibers combine to define thickness of yam. Denier is a common term to classify yarn and is theweight in grams of 9000 meters of yarn length. A yarn of a desired denier may be formed by using several fine fibers or few coarser fibers. Highly precise weaving is used with one or more types of yarns to form various patterns and textures for the cover. Preferably, a weaving technique known as Terry may be used and which involves forming free standing loops across the whole surface of the fabric or in a predetermined pattern. The loops are formed on an outer side (top side or top surface) of the base of the cover that contacts the wafer. The loops thus formed can be left in closed form or cut to create free standing fibers. Due to their ability to flex, free standing loops or fibers allow for a more uniform contact and fluid transport at the wafer-brush pad interface than a standard flat brush pad surface.

[0057] In another embodiment, the base of the cover may be made first using for example polyolefin fibers arranged into a web or mat using a non-woven fabric production method including, for example, a carding, air-laid, or melt blown process where the fibers are entangled or bonded together to form the non-woven structure of the base of the cover. Then the free-standing fibers and or fiber loops may be formed using a process called tufting. Tufting machines have needles that push the fibers through the non-woven fabric base to form protruding loops in any desired pattern. When the tufting method is used the loops are secured in place by applying a porous backing to the back side of the fabric base which is fluid when applied and solidifies after application to hold the fibers locked in place. The non-woven material of the base of the cover may be, for example, a non-woven material made of polyolefins such as polyethylene and / or polypropylene. The non-woven polyolefin cover may be made using any suitable nonwoven manufacturing process including, for example, a spunbond process, a meltblown process, or a combination thereof. These processes are well known in the non-wovenfabric industry and therefore are not discussed in detail here. The non-woven material may be formed in any suitable shape.

[0058] The loops can be arranged in a pattern, for example, in multiple circumferential rings with the number of the rings arranged across the length or in horizonal lines which span part or entire length of brush pad. Another example of a pattern is a spiral pattern. A spiral pattern arrangement provides a preferential direction motion along the diameter of the wafer. Loops could also be laid across the brush pad surface, in a geometric form such as grouped into squares of circles of a given size and pitch. The present invention composite brush pad design with the microporous core and the cover allows optimization of the cleaning efficiency and substantial reductions in DIW consumption.

[0059] According to an embodiment, the present invention allows for woven or knitted fiber loops or freestanding fiber patterns on the surface of the cover, i.e., a near limitless number of configurations for optimal layout and therefore cleaning efficiency. The diameter of the yarn is an important factor as the interaction between yarn and wafer debris is key to removal of particles and residues from the wafer surface. As the yarn diameter increases the stiffness of each free standing fiber and or each loop increases and as the extension length of each free standing fiber and or each loop increases, its flexibility and deflection increases. Mechanical properties of the fibers forming yam also impact the stiffness and deflection. According to the present invention, brush pad construction can therefore be modulated with a combination of fiber material, individual fiber diameter and yam diameter as well as loop extension and loop density.

[0060] Besides mechanical action from the loops, surface properties such as zeta potential of the loop material play an important role in cleaning effectiveness. The yarnmaterial needs to be selected such that loops exert repulsive force onto the particles in addition to the mechanical flexing force. Zeta potential refers to the electric potential difference between electrical double layer of a solid surface with reference to the solution. The zeta potential may therefore be positive or negative. When loops and abrasive have opposite zeta potentials, it sets up an attractive force between the loop and abrasive particle, which will lead to abrasive adhering to the loops. For effective cleaning, the zeta potential of yarn material needs to be same sign as the abrasive being removed. Fibers with different zeta potentials maybe may be combined to tune the zeta potential of the yam for maximum cleaning ability. Therefore, zeta potential tuning is an important element of cleaning ability of the brush pads. Nylon has zeta potential of +40 mV at PH of 2, while polyester has zeta potential of -10 mV and PVA is near 0 mV. It is expected nylon loops will be effective with cleaning ceria nano particles, which have reported zeta potential values of +40 mV at PH 2, while polyester brush pad will be filled with ceria particles quickly due to charge attraction. Similarly, nylon has a zeta potential of -80 mV at Ph 10 and higher, polyester has a zeta potential of -40 mV at PH 10, while ceria has a zeta potential of -30 mV at PH 10. Nylon and polyester, both can therefore provide effective cleaning for ceria nanoparticles in alkaline PH. Nylon, PVA and polyester fibers maybe combined to generate appropriate PH vs Zeta potential curve for optimal cleaning.

[0061] Mechanical properties of the yarn play an important role in the knitting and weaving process. For example, it is more difficult to maintain dimensional stability and loop height when using elastomeric yams. In this case more elastomeric fibers may be combined with less elastomeric fibers before performing the weaving or knitting operation.

[0062] According to an embodiment, the brush pad comprises a composite cylindrically shaped and microporous core with open cell pores forming microchannels through which the DIW flows from its inner surface to its outer surface. A cover is securely positioned on the outer surface of the core. The cover comprises a base made of fabric and fiber loops formed on the top (or outer surface) of the base. The fiber loops may be arranged preferably in a nodular pattern. The brush pad has a first core flow resistance Rl, a second through-surface flow resistance of the base of the cover R2, and a third flow resistance R3 across the surface of the free-standing fibers and or the fiber loops, wherein R3<R1<R2. The flow resistance Rl, R2, R3 describes water resistance per unit thickness in the direction of flow at a given water supply pressure. The flow resistances provide an indication of how easily does the water flow through the three sections of the composite brush pad, i.e., the core, the base of the cover, and the loops and or freestanding fibers. In contrast, to the conventional brush of figure 1, the inventive brush pad has different first and second flow resistances Rl and R2. Also, the third flow resistance R3 across the surface of the free-standing fibers and or the fiber loops is very different than the flow resistance across the solid nodules of a conventional brush.

[0063] In an embodiment, the microporous core may be made of polyolefin, e.g., polypropylene used in water filtration applications. Melt blown polypropylene filter cartridges are available in several pore sizes and are particularly suited for this application. The manufacturing process involves melt-blown technology, where the polypropylene is melted and extruded in fibers which are then collected on a rotating drum to create a non-woven matrix with a high surface area. The melt-blown PP cartridge has a web-like structure with interconnected voids or pores between the pores. The size of these voids can be controlled by the manufacturing process. Preferably the pores or voidsthrough the non-woven matrix may have a diameter of at from 1 to 50 micrometers, or from 2 to 40 micrometers, or 3 to 20 micrometers. Higher or lower pore sizes may also be used depending on requirements.

[0064] Melt blown filter cartridges of other materials may also be used such as from polyester (PE), polyamide (PA or Nylon), polytetrafluoroethylene (PTFE), and polyethersulfone (PES), preferably polyester and polyamide.

[0065] Open cell, microporous PVA (polyvinyl acetate), urethane or a wound filament filter may also be used.

[0066] In an embodiment, the yam loops may be Terry fiber loops formed by weaving or knitting. The cover surface weave density may be higher than a core brush pad density. The core may have a pore percentage from 60 to 90 % and a cover fabric surface may have a pore percentage of from 40 to 70 %. Higher or lower percentages may be used, as long as, core porosity is higher than the cover fabric porosity.

[0067] In an embodiment the brush pad core may have a cylindrical shape with a radius of 20 mm to 70 mm, and the cover may have the form of a cylindrical sleeve positioned around the cylindrical core. The sleeve-shape core may have a thickness of 1-2 mm, and the yam loops and or freestanding fibers may have a free-standing height of 2-5 mm

[0068] In another embodiment, the cover of the brush pad may have a disc (Fig 2C) or prismatic shape.

[0069] The inner surface of the core is configured to connect with the fluid mandrel and receive the DIW which is then flown through the porous network of the core then out of the outer surface of the core and into the cover of the brush pad.

[0070] For example, the inner surface of the core may form a cylinder configured to couple with the fluid mandrel of the wafer cleaning apparatus. However, the inner surface of the core may also in other embodiments have a rectangular cross-section The core may further include an inlet configured to fluidly connect with a fluid mandrel of a wafer cleaning apparatus. Cleaning fluid, e.g., DIW alone or with one or more cleaning chemicals may be directed from the fluid mandrel into the inlet of the core and from there pass through the porous network of the core and through the cover to reach the surface of the wafer that is subjected to the cleaning operation.

[0071] The yarn may be made of polymer fibers made of at least two of polyolefin, polyester, nylon, polyurethanes, polyvinyl alcohol (PVA), polyvinyl acetate, or engineered fibers such as poly-para-phenylene terephthalamide, aromatic polyamide, polytetrafluoroethylene (PTFE), and ultra-high molecular weight polyethylene.

[0072] In a conventional brush the matrix material is constrained by larger matrix of single material and near range connections to the matrix. By contrast according to the present invention brush pad, the individual nature of loops and fiber extension enables more efficient contact with particles and debris on the wafer. Additionally, mechanical and electrokinetic properties can be easily tuned by combining fibers of different materials. The invention thus provides an engineered surface design for the brush pad which exhibits improved cleaning efficiency by enabling fiber loops with tuned mechanical and electrokinetic properties. New design enables improved cleaning, while reducing DIW and cleaning chemical consumption.

[0073] It is understood that Terry is one method for creating surface texture by weaving or knitting. There are other weaving / knitting patterns that may also be used to generate the 3D fiber loop or freestanding fiber structures useful for the application. Anadvantage of the PCMP brush pad of the present invention is that it provides significant reduction in DIW usage compared to existing PCMP brushes.

[0074] The present invention enables decoupling pore percentage / pore size from compressibility thereby enabling lower water usage while enabling improved cleaning efficiency.

[0075] FIG. 2(A) is a simplified schematic of a brush pad according to an embodiment of the present invention. Fig 2(B) shows a cross section of the same. Referring now to FIGS. 2(A) and 2(B) a brush pad generally designated with numeral 200 is provided according to the present invention. The brush pad 200 includes a core 201 having an inner surface 20 IB and an outer surface 201 A. The core 201 is mounted with its inner surface 20 IB onto a mandrel 203. The core 201 may have a cylindrical shape. The core 201 may be a microporous core having a plurality of interconnected pores allowing fluid flow therethrough.

[0076] The brush pad 200 further comprises a fabric made (made form textile fibers) sleeve 206 with a sleeve base 205 and fiber loops 202 on the sleeve base 205. In a one embodiment, all fiber loops may be made of the same polymer. In another preferred embodiment shown in FIG. 2(C), the brush pad has a disc shape wherein one side of the brush is coupled to the mandrel (203) that fluidly connects it to DIW and the opposite surface is covered with loops (202) and contacts the wafer. The fiber loops 202 may include at least two types of loops 202A and 202B, each made of different polymer material designed to have different cleaning activity or affinity for different types of impurities. For example, the 202A type of fibers may be made with nylon fiber and the 202B type of fibers may be made with PVA. Or, the 202A type of fibers may be madewith nylon and polyester filaments, while the 202B type of fibers may be made with polyester and PVA filaments.

[0077] The cover 206 is securely attached to the outer surface of the core 201 while additional DIW spray 204 is applied during cleaning. In operation, DIW provided by the mandrel 203 flows through the open pores / micro-channels of the core into the base of the cover 205 and out of the base of the cover onto the loops and onto the wafer surface which is being cleaned. Additional DIW spray 204 may also be sprayed during cleaning. The brush pad may be mounted in existing wafer cleaning apparatuses to replace existing wafer brushes. In an example operation, a wafer may be positioned between two rotating brush pads. Depending on the shape of the brush pad the rotational movement may differ. For example, for a cylindrical brush pad may rotate around a central longitudinal axis of symmetry passing through the center line of the core of the brush pad. By contrast a disc shape (Fig. 2(C)) or prismatic shape brush pad may rotate around an axis passing vertically to the outer flat surface of the disc or prism of the brush pad that passes from the center of the circle or rectangular shape surface of the brush pad. Hence, the invention as disclosed can be implemented with different wafer cleaning apparatuses and is not limited to cylindrical sleeve shape brush pads.

[0078] Figure 3 shows a close-up of a fiber loop 202 acting upon a particle defect 302 on the surface 301 of a wafer 300. The present invention brush pad allows a synergistic effect between the water action and the fiber loop action for cleaning any defects and / or impurities from the surface of the wafer, thus allowing substantial savings in water usage without compromising the effectiveness of the cleaning.

[0079] As conventional brush is made of homogeneous material composition, flow resistance in the brush pad core, surface and nodules is the same Rl. The presentinvention PCMP brush pad has a core flow resistance of Rl, a flow resistance at brush pad surface R2 and a flow resistance through the cover surface R3 which are different, and preferably, for optimal performance R3 is less than Rl, and Rl is less than R2, i.e., R3<R1<R2. Flow resistance R2 can be tuned by the density of the fiber weave / knitting. A dense weave results in higher pressure drop, while a light weave results in lower pressure drop. Pressure drop at the surface is important since it impacts a backflow of the cleaning particles. Higher pressure drop minimizes potential for backflow of the cleaning particles. Additionally having a lower surface fluid flow resistance of the cleaning fiber loops R3 also preferentially directs the flow across the brush pad surface. A surface weave density higher than the core brush pad density is desirable in controlling R2. In an embodiment the pore percentage of brush pad core is from 70 to 90% while the pore percentage of the cover fabric surface is from 50 to 70%.

[0080] Higher or lower pore percentages maybe used if the core porosity is higher than the porosity of the cover surface. The core may have graded porosity such that surface of the core has lower porosity than the bulk of the core. In this case the surface of core and cover may have similar resistance ~R2. The material and design of fibers used to construct the fiber loops has an impact on cleaning efficiency. Flexing force imparted by yam maybe modulated through fiber material properties, fiber, and yam diameter as well as free extension of loops above the surface. Suitable materials for the fibers include polymer fibers including polyester, nylon, polyurethanes, polyvinyl alcohol, polyvinyl acetate as well as engineered fibers such as poly-para-phenylene terephthalamide traded under the name Kevlar® by Dupont, aromatic polyamide (also known as aramid), polytetrafluoroethylene (PTFE) traded under the name Teflon® by DuPont, ultra-high molecular weight polyethylene (UHMWPE) and the like. Fiber material may be chosensuch that, while some softening from water absorption may be desirable, properties are not significantly impacted by prolonged exposure to water and cleaning chemicals. It is desirable to use yarn with smaller diameter. Preferably the yam may be a relatively fine yam having a diameter of 2000 microns or less, or 1000 micron or less. More preferably, the yarn may be made of at least a plurality of fibers each microfiber having a diameter of less than 100 microns, or less than 50 microns, or less than 40 microns or less than 10 microns. For example, the yam may be made of a plurality offibers having a diameter of 5 to 200 microns, or 5 to 100 microns, or 5 to 50 microns. The plurality of microfibers making the yam may vary. For example, the yam may be made of 5 to 200 fibers, or 5 to lOOfibers, or 5 to 50 fibers, or 15 to 200 fibers, or 15 to 100 fibers, or 15 to 50 fibers. The yam may comprise one or more type of fibers, for example, a yarn may be made solely of one type of fibers, or may be made of two or more types of fibers. For example, in an embodiment, the yarn may be made of polyester and PVA fibers.

[0081] The fibers making the yarn may be made of different materials as described above. In an embodiment, the fibers may be made of polyester, or PVA, or a combination thereof. For example, the yam may be made of a plurality of polyester and or PVA fibers.The extension of the fiber loops or of the fibers above the free surface impacts their stiffness with shorter extension loops or fibers exhibiting higher stiffness than longer extension. Electrokinetic properties such as zeta potential also play an important role in cleaning performance. Efficient wafer cleaning requires good, uniform contact between wafer and brush pad surface as well as matching positive / negative zeta potential of brush pad material to be the same sign as the particle. Brush pad surface flatness is a function of the uniformity of microporous core and outer woven sleeve. As the gap between waferand brush pad is reduced increasing number of loops contact the wafer surface until substantially all loops are touching the wafer surface. Overall surface height of loops needs to be controlled to allow uniform contact with minimal loop compression. The gap can then be adjusted to tune cleaning pressure. In an embodiment, loops having a nominal extension in the range of 1-5 mm maybe employed.

[0082] Examples

[0083] Cover

[0084] Example 1 : In one embodiment the cover was made with yam made of 30 polyester fibers each having diameter of approximately 25 microns. The cover base had fiber density of approximately 40 (X+Y) per cm2and loop density of 200 / cm2. The loop height was 4 mm. A top view of the cover with the nodular pattern is shown in Figure 5. The individual nodules are made of a cluster of fiber loops. This is to be contrasted with the nodules of Figure 4 which shows a simplified schematic of a conventional PVA brush with plurality of PVA nodules on its surface. The nodules of Figure 4 have a diameter of 10 mm and are 5 mm high.

[0085] Example 2: In another embodiment, the cover was made with yam made of 15 polyester fibers and 15 PVA each having diameter of approximately 25 and 26 microns respectively. The cover base had fiber density of approximately 40 (X+Y) per cm2. Loops were arranged in 25mm x 10mm square nodule with 5 mm spacing. The loop density in the nodules was 200 / cm2. The loop height was maintained at 4mm.

[0086] Examples of the composite brush pad

[0087] Examples 3 and 4

[0088] The covers of the Examples 1 and 2 were securely attached on the outer surface of a polypropylene filter model AVS20M20 made by Parker Inc, using 3M™ HotMelt Adhesive 3764, applied with 3M AE GEN II Glue Gun model Hl 1043.hotmelt adhesive. The filter cartridge with 62.5mm outer diameter, was cut to match 218 mm length required to fit Ontrak Synergy wafer cleaner, made by Lam Corporation. A Mandrel was securely attached to the inside diameter of the filter core, prior to attaching the sleeve, to supply cleaning fluid through the center. The cylindrical assembly had outer diameter of 2.5 inches with 3mm loop height to match final brush pad diameter spec of 72 mm.

[0089] Examples 5 and 6

[0090] The covers of examples 1 and 2 were securely attached, using hotmelt adhesive, on the outer surface of a filter cartridge model SP-P25-20 of SpiroPure Inc, which is pre-attached to the mandrel on the inside diameter. The outer diameter is 2.5 inches and is rated for 25 -micron particulate removal. The inside diameter and outside diameter of the filter core are pre-machined as needed to meet the dimension specification.

[0091] Examples 7 and 8

[0092] The covers of examples 1 and 2 were securely attached, using hotmelt adhesive, on the outer surface of filter cartridge model SP-P50-20 of SpiroPure Inc. which had the same dimensions as the SP-P25-20 model and was rated for 50-micron particulates.

[0093] Examples 9 and 10

[0094] The covers of examples 1 and 2 were securely attached using hotmelt adhesive to the outer surface of filter cartridge model SP-P50-20 of Spiropure Inc. The length was adjusted to 318 mm to make brushes for Applied Materials PCMP brushcleaner used for 300mm wafers. Mandrel suitable for fluidly connecting with AppliedMaterials PCMP cleaner was pre-attached to the inside diameter of the filter.

[0095] 200mm brushes, from example 3 and 4 were installed on Ontrak scrubber for testing wafer cleaning performance. Only wafer frontside brush was changed to the new brushes, while standard PVA brush was used for as the backside brush. 200mmPECVD oxide wafers were processed through the cleaner as clean, slurry dipped, as well as with 50% DIW flow through the brushes. Wafers were measured on Tencor 6420 for detectivity. Cleaning performance was maintained with 50% lower DIW flow. Good cleaning efficiency was demonstrated with slurry dipped wafers. Hence, substantial improvements in cleaning efficiency and reduction in water consumption were obtained with the brush pads of examples 3 and 4 compared to a conventional PVA brush with nodules as the one illustrated in Figure 1.

[0096] Although the invention has been described with specific embodiments it should be understood, that many other embodiments may be envisaged by those skilled in the art to which the present invention pertains without departing from the scope or spirit of the present invention as defined by the following claims.

Claims

AMENDED CLAIMS received by the International Bureau on 04 June 2025 (04.06.2025)1. A brush pad for semiconductor wafer cleaning, the brush pad comprising: a microporous core having an inner surface and an outer surface and a network of interconnected open micropores fluidly connecting the inner surface with the5 outer surface; and a cover positioned over an entire outer surface of the core, wherein the inner surface of the core is configured to connect to a cleaning fluid mandrel of a wafer cleaning apparatus for receiving a cleaning fluid and allowing the cleaning fluid to pass through the network of interconnected open micropores of the core to the outer surface and into the10 cover, wherein the cover comprises a woven or knitted fabric with a plurality of freestanding fibers and / or fiber loops extending above an outer surface of the cover and an inner surface attached to the outer surface of the core, wherein the freestanding fibers and or fiber loops are made of at least15 two different types of fibers, and wherein the loop density is at least 100 loops / cm22. The brush pad of claim 1, wherein the core has a cylindrical, disc, or prismatic shape,20 wherein the cover has a cylindrical, disc, or prismatic shape, wherein the cover is attached to the core via an adhesive and wherein the freestanding fibers are substantially perpendicular to the brush pad surface.

3. The brush pad of claim 1 , wherein the fibers are selected from single polymer fibers or fibers made from a combination of polymers comprising polyolefin, polyester, nylon, polyurethanes, polyvinyl alcohol (PVA), polyvinyl acetate, or engineered fibers such as poly-para-phenylene terephthalamide, aromatic polyamide, polytetrafluoroethylene5 (PTFE), and ultra-high molecular weight polyethylene, preferably, polyester, nylon, and polyvinyl alcohol (PVA).

4. The brush pad of claim 1 , wherein the cover has a cylindrical sleeve shape positioned securely around the core, and wherein the freestanding fibers and or fiber loops are10 substantially perpendicular to the brush pad surface.

5. The brush pad of claim 1, wherein PVA fibers and polyester fibers are combined to make the freestanding fibers and / or the loops.15 6. The brush pad of claim 1 , wherein polyester fibers and nylon fibers are combined to make the freestanding fibers and / or the loops.

7. The brush pad of claim 1, wherein the microporous core is made of a microporous plastic material or20 composite plastic material comprising micro-channels and / or open pores allowing water to flow from the inner surface of the core through the core and out of the outer surface of the core into the cover, and wherein the individual freestanding fibers and individual fiber in loops are 10 micron to 200 micron in diameter, preferably 10 to 100 microns in diameter, and morepreferably 1 to 50 microns in diameter and extend 0.5 mm to 10 mm in height above the outer surface, preferably 1.0 mm to 7 mm in height above the outer surface of the sleeve, and more preferably 2.0 mm to 5.0 mm in height above the outer surface of the cover.5 8. The brush pad of claim 1, wherein the fiber density of the base of the sleeve is 20 yams (X+Y) per cm2to 200 yams per cm2, preferably 25 per cm2to 180 yams (X+Y) per cm2, more preferably 40 yams (X+Y) per cm2to 150 yams (X+Y) per cm2, and even more preferably from 60 yams (X+Y) per cm2to 120 yams (X+Y) per cm2.10 9. The brush pad of claim 1, wherein the freestanding fiber and / or fiber loop density is100 loops per cm2to 1000 loops per cm2, preferably 100 per cm2to 900 loops per cm2, more preferably 100 per cm2to 600 loops per cm2, and even more preferably 150 per cm2to 400 loops per cm2.15 10. The brush pad of claim 1, wherein the fibers and / or fiber loops are arranged in a pattern including linear, circumferential, spiral, arc, nodular, or some other geometric pattern, preferably nodular or spiral.

11. The brush pad of claim 1, wherein each loop is made by combining the fibers of two20 different materials.

12. The brush pad of claim 1, wherein the freestanding fibers and / or fiber loops are formed together with the base of the sleeve on the surface of the sleeve in a single weaving or knitting process, andwherein loops are made of at least two different fibers, and wherein the core is made of open cell microporous PVA, polyolefins such as polypropylene, polyurethane preferably polypropylene and PVA5 13. The brush pad of claim 1, wherein the core is made of a nonwoven polypropylene filter cartridge.

14. The brush pad of claim 1, wherein the core is made of a melt-blown polymer.1015. A brush pad for semiconductor wafer cleaning, the brush pad comprising: a composite microporous core with open cell pores; and an outer cover disposed on the outer surface of the microporous core, the outer cover15 comprising a fabric made base and freestanding fibers or fiber loops on the fabric base and extending above a top surface of the base of the cover, wherein the loops are made of at least two different fibers, wherein the core has a cylindrical, disc, or prismatic shape, wherein the cover has a cylindrical, disc, or prismatic shape,20 wherein the cover is attached to the core via an adhesive, wherein the freestanding fibers extend substantially normal to the brush surface,wherein the brush pad has a first core flow resistance RI through the microporous core, a second flow resistance R2 through the base of the cover, and a third flow resistance R3 across the surface of the loops, and wherein R3<R1 <R2.

516. The brush pad of claim 15, wherein the loops are Terry fiber loops formed by weaving or knitting together with the base of the cover in a single process.

17. The brush pad of claim 15,10 wherein a cover weave density is higher than a core brush pad density, and wherein the core has a pore percentage of from 60% to 90 % and the cover base has a pore percentage of from 40% to 70 %.

18. The brush pad of claim 15, wherein the yarn fibers are polymer fibers made of at least15 one of polyolefins, polyester, nylon, polyurethanes, polyvinyl alcohol (PVAc), polyvinyl acetate, or engineered fibers such as poly-para-phenylene terepthalamide, aromatic polyamide, polytetrafluoroethylene (PTFE), and ultra-high molecular weight polyethylene.20 19. A brush pad for semiconductor wafer cleaning, the brush pad comprising: a microporous core having a disc or prismatic shape with a first surface of the brush pad being configured to be fluidly coupled to a DIW supply, and a network of pores fluidly connecting the first surface to the second surface wherein in operation DIW flowsin the microporous core through the first surface and through the network of pores reaches the second surface; a cover comprising a base made of woven fabric, knitted fabric, or non-woven fabric, and at least two types of free standing fibers or fiber loops arranged in a pattern of5 nodules, each type of the free standing fibers or fiber loops made of a different material designed to have different cleaning activity or affinity for different types of impurities.

20. The brush pad of claim 19, wherein a first type of freestanding fibers and or fiber loops are made with nylon,10 polyester, or a combination thereof and a second type of fibers and or fiber loops are made with polyester, PVA, or a combination thereof.

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