Patent Publication Number: US-9884400-B2

Title: Polishing pad and method for making the same

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a polishing pad and a method for making the same, and more particularly, to a polishing pad having hollow structures and a method for making the same. 
     2. Description of the Related Art 
       FIG. 1  and  FIG. 2  are schematic views of a method for making a conventional polishing pad. The method for making the conventional polishing pad is as follows. A resin  10  (usually a thermoplastic polyurethane polymeric foam) is infused into a mold cylinder, to form a bulk  11  after cooling and solidification. As shown in  FIG. 1 , the bulk  11  has a plurality of cells  12 . Then, referring to  FIG. 2 , the bulk  11  is cut along a plurality of cutting lines  13  to form a plurality of polishing pads  14 . The polishing pads  14  have independent bubble structures, and are usually used in high planarization polishing. However, the main problem of the polishing pads  14  lies in that, because the concentration distribution of the resin  10  in the mold cylinder is less uniform, during molding, the difference between temperature distributions in various positions of the mold cylinder may result in that the cells  12  have different sizes and distributions and the cells  12  are not easy to control. Thus, after a slicing process, the different sizes of the cells  12  on the slicing surfaces of the polishing pads  14  will become more obvious. During the grinding process, a grinding slurry permeates into large-aperture cells and small-aperture cells by different degrees, which will cause nonuniform grinding and deposition of the grinding slurry, thus easily producing grinding defects. 
     Therefore, it is necessary to provide an innovative and progressive polishing pad and a method for making the same, so as to solve the above problems. 
     SUMMARY OF THE INVENTION 
     The present invention provides a polishing pad. The polishing pad comprises a polymeric elastomer and a plurality of hollow structures. The hollow structures are uniformly distributed in the polymeric elastomer, and the sizes of the hollow structures are substantially equal to each other. Thereby, during the polishing process, when the hollow structures have broken holes, or the hollow structures are all removed to leave cells, the grinding slurry permeates into the polishing pad by the same degree, which thus can improve the grinding effect. 
     The present invention further provides a method for making a polishing pad. The method comprises the steps of: (a) mixing a plurality of hollow structures into a polymeric resin, wherein the sizes of the hollow structures are substantially equal to each other, and the hollow structures are distributed in the polymeric elastomer uniformly; (b) coating a portion of the polymeric resin onto a carrier, to form a first polymeric layer, wherein the first polymeric layer comprises at least one row of hollow structures; (c) curing the first polymeric layer; (d) coating a portion of the polymeric resin onto the first polymeric layer, to form a second polymeric layer, wherein the second polymeric layer comprises at least one row of hollow structures; (e) curing the second polymeric layer; and (f) repeating the steps (d) to (e) at least once, to form a polishing pad. 
     The present invention further provides a method for making a polishing pad. The method comprises the steps of: (a) providing a polymeric resin, and coating a portion of the polymeric resin onto a carrier, to form a first polymeric layer; (b) embedding a plurality of first hollow structures to an upper surface of the first polymeric layer, such that a lower portion of each of the first hollow structures is located in the first polymeric layer, and an upper portion of each of the first hollow structures is exposed from the first polymeric layer, wherein the sizes of the first hollow structures are substantially equal to each other, and the first hollow structures are distributed on the upper surface of the first polymeric layer uniformly; (c) curing the first polymeric layer; (d) coating a portion of the polymeric resin onto the first polymeric layer, to form a second polymeric layer, wherein the second polymeric layer covers the first hollow structures; (e) embedding a plurality of second hollow structures to an upper surface of the second polymeric layer, such that a lower portion of each of the second hollow structures is located in the second polymeric layer, and an upper portion of each of the second hollow structure is exposed from the second polymeric layer, wherein the sizes of the second hollow structures are substantially equal to each other, and the second hollow structures are distributed on the upper surface of the second polymeric layer uniformly; (f) curing the second polymeric layer; and (g) repeating the steps (d) to (f) at least once, to form a polishing pad. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  and  FIG. 2  are schematic views of a method for making a conventional polishing pad. 
         FIG. 3  to  FIG. 6  are schematic views of process steps of a method for making a polishing pad according to an embodiment of the present invention. 
         FIG. 7  to  FIG. 12  are schematic views of process steps of a method for making a polishing pad according to another embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PRESENT INVENTION 
       FIG. 3  to  FIG. 6  are schematic views of process steps of a method for making a polishing pad according to an embodiment of the present invention. Referring to  FIG. 3 , a plurality of hollow structures  22  are mixed into a polymeric resin  20 , where the sizes D of the hollow structures  22  are substantially equal to each other, and the hollow structures  22  are distributed in the polymeric resin  20  uniformly. The material of the polymeric resin  20  is selected from the group consisting of polyamide resin, polycarbonate, polymethacrylic resin, epoxy resin, phenolic resin, polyurethane resin, vinylbenzene resin and acrylic resin, and the material of the hollow structures  22  is waterborne polyurethane or acrylic resin. In this embodiment, the material of the polymeric resin  20  is acrylic resin, for example, epoxy acrylate, urethane acrylate, polyester acrylate or polyether acrylate. The material of the hollow structures  22  is waterborne polyurethane. 
     In this embodiment, each of the hollow structures  22  is a capsule-like structure, which has a closed space formed by a shell  221 . Preferably, the hollow structures  22  are spherical. The sizes D of the hollow structures  22  range from 10 μm to 100 μm, and the size variation between the hollow structures  22  is within 20%. In this embodiment, the sizes D of the hollow structures  22  range from 30 μm to 40 μm. In this embodiment, the hollow structures  22  are first treated to be charged. In this embodiment, the hollow structures  22  are charged through electrospray extrusion injection, and an implementation mode thereof is as follows. At first, a metal capillary is provided, where the metal capillary has a spray nozzle. At the same time, a corresponding electrode is placed in a position at a distance of 1 cm to 2 cm from an outlet of the spray nozzle. Next, a sample of an aqueous solution containing the hollow structures  22  is injected to the metal capillary, and thousands of volts of potential difference (the voltage is preferably 5-30 kV, and is more preferably 10-20 kV) is applied between the metal capillary and the corresponding electrode. In this way, when being sprayed from the spray nozzle, the hollow structures  22  will be charged. 
     Next, a portion of the polymeric resin  20  is coated (for example, blade coating) onto a carrier  23 , to form a first polymeric layer  24 . The first polymeric layer  24  includes at least one row of hollow structures  22 . In this embodiment, the thickness of the first polymeric layer  24  is very thin through blade coating and by controlling appropriate process parameters, so that the first polymeric layer  24  only includes one row of hollow structures  22 . Because the hollow structures  22  have already undergone through the above-mentioned electrospray extrusion injection, the hollow structures  22  have positive charge on the surfaces thereof. As like charges repel, the hollow structures  22  may be arranged in the first polymeric layer  24 , but aggregation or coagulation will not occur. Preferably, the hollow structures  22  are located in central positions of the first polymeric layer  24 . It can be understood that horizontal positions of the hollow structures  22  may slightly deviate from each other, that is, some hollow structures  22  may be higher while some may be lower. 
     In another embodiment, whether the hollow structures  22  are charged or not, after the polymeric resin  20  is coated, a flat scraper can be used to scrape excessive polymeric resin  20  and hollow structures  22  by controlling appropriate process parameters, such that the first polymeric layer  24  only includes one row of hollow structures  22 . 
     Next, the first polymeric layer  24  is cured or hardened through irradiation of UV light or heating. In this embodiment, the first polymeric layer  24  is cured through irradiation of UV light, and the irradiation time is 1 minute to 1 hour. The polymeric resin  20  is cured or hardened through bonding of two bonds in oligomer and monomer thereof. 
     Referring to  FIG. 4 , a portion of the polymeric resin  20  is coated (for example, blade coating) onto the first polymeric layer  24 , to form a second polymeric layer  26 , where the second polymeric layer  26  includes at least one row of hollow structures  22 . In this embodiment, the second polymeric layer  26  includes one row of hollow structures  22 , and the hollow structures  22  are arranged in the second polymeric layer  26  in a same manner as that in which the hollow structures  22  are arranged in the first polymeric layer  24 . Preferably, the hollow structures  22  are located in central positions of the second polymeric layer  26 . 
     Next, the second polymeric layer  26  is cured or hardened through irradiation of UV light or heating. In this embodiment, the second polymeric layer  26  is cured or hardened through irradiation of UV light, and the irradiation time is 1 minute to 1 hour. The polymeric resin  20  is cured or hardened through bonding of two bonds in oligomer and monomer thereof. 
     Referring to  FIG. 5 , the steps in  FIG. 4  are repeated at least once, to form at least one polymeric layer  28  on the second polymeric layer  26 , where the polymeric layers  24 ,  26  and  28  form a polymeric elastomer  30 , and the materials of the polymeric layers  24 ,  26  and  28  may be the same or different. 
     Referring to  FIG. 6 , the carrier  23  is removed, to form a polishing pad  3 . 
       FIG. 6  is a schematic cross-sectional view of a polishing pad according to an embodiment of the present invention. The polishing pad  3  comprises a polymeric elastomer  30  and a plurality of hollow structures  22 . The hollow structures  22  are uniformly distributed in the polymeric elastomer  30 , and the sizes D of the hollow structures  22  are substantially equal to each other. In this embodiment, the polymeric elastomer  30  is formed by curing a polymeric resin  20 . The material of the polymeric resin  20  is selected from the group consisting of polyamide resin, polycarbonate, polymethacrylic resin, epoxy resin, phenolic resin, polyurethane resin, vinylbenzene resin and acrylic resin, and the material of the hollow structures  22  is waterborne polyurethane or acrylic resin. In this embodiment, the material of the polymeric resin  20  is acrylic resin, for example, epoxy acrylate, urethane acrylate, polyester acrylate or polyether acrylate. The material of the hollow structures  22  is waterborne polyurethane. 
     In this embodiment, each of the hollow structures  22  is a capsule-like structure, which has a closed space formed by a shell  221 . Preferably, the hollow structures  22  are spherical. The sizes D of the hollow structures  22  range from 10 μm to 100 μm, and the size variation between the hollow structures  22  is within 20%. In this embodiment, the sizes D of the hollow structures  22  range from 30 μm to 40 μm. In this embodiment, the hollow structures  22  are charged. 
     In this embodiment, the polymeric elastomer  30  includes a plurality of polymeric layers  24 ,  26  and  28 . Each of the polymeric layers  24 ,  26  and  28  includes one row of hollow structures  22 . The row of hollow structures  22  are located in central positions of each of the polymeric layers  24 ,  26  and  28 . 
     During polishing process, as the hollow structures  22  have substantially the same sizes and are uniformly distributed in the polishing pad  3 , when the hollow structures  22  have broken holes (meanwhile, the hollow structures  22  are cells), or the hollow structures  22  are all removed to leave cells, the grinding slurry permeates into the polishing pad  3  by the same degree, which thus can improve the grinding effect. In other words, the cells of the polishing pad  3  are not formed through foaming 
       FIG. 7  to  FIG. 12  are schematic views of process steps of a method for making a polishing pad according to another embodiment of the present invention. Referring to  FIG. 7 , a polymeric resin  20  is provided. The material of the polymeric resin  20  is selected from the group consisting of polyamide resin, polycarbonate, polymethacrylic resin, epoxy resin, phenolic resin, polyurethane resin, vinylbenzene resin and acrylic resin. In this embodiment, the material of the polymeric resin  20  is acrylic resin, for example, epoxy acrylate, urethane acrylate, polyester acrylate or polyether acrylate. 
     Next, a portion of the polymeric resin  20  is coated (for example, blade coating) onto a carrier  23 , to form a first polymeric layer  24 . 
     Referring to  FIG. 8 , a plurality of first hollow structures  22   a  are embedded to an upper surface  241  of the first polymeric layer  24 , such that a lower portion of each of the first hollow structures  22   a  is located in the first polymeric layer  24 , and an upper portion of each of the first hollow structures  22   a  is exposed from the first polymeric layer  24 . In this embodiment, the first hollow structures  22   a  are charged through the above-mentioned electrospray extrusion injection. The first hollow structures  22   a  are sprayed from the spray nozzle to the upper surface  241  of the first polymeric layer  24 before the first polymeric layer  24  is cured. Meanwhile, since the first polymeric layer  24  has not been cured, the first hollow structures  22   a  are embedded to the upper surface  241  of the first polymeric layer  24  due to the gravity thereof. 
     The sizes D of the first hollow structures  22   a  are substantially equal to each other, and the first hollow structures  22   a  are distributed on the upper surface  241  of the first polymeric layer  24  uniformly. In this embodiment, each of the first hollow structures  22   a  is a capsule-like structure, which has a closed space formed by a shell  221 . Preferably, the first hollow structures  22   a  are spherical. The sizes D of the first hollow structures  22   a  range from 10 μm to 100 μm, and the size variation between the first hollow structures  22   a  is within 20%. In this embodiment, the sizes D of the first hollow structures  22   a  range from 30 μm to 40 μm. The material of the first hollow structures  22   a  is waterborne polyurethane or acrylic resin. In this embodiment, the material of the first hollow structures  22   a  is waterborne polyurethane. 
     Next, the first polymeric layer  24  is cured or hardened through irradiation of UV light or heating. In this embodiment, the first polymeric layer  24  is cured through irradiation of UV light, and the irradiation time is 1 minute to 1 hour. The polymeric resin  20  is cured or hardened through bonding of two bonds in oligomer and monomer thereof. 
     Referring to  FIG. 9 , a portion of the polymeric resin  20  is coated (for example, blade coating) on the first polymeric layer  24 , to form a second polymeric layer  26 . The second polymeric layer  26  covers the upper surface  241  of the first polymeric layer  24  and the first hollow structures  22   a.    
     Referring to  FIG. 10 , a plurality of second hollow structures  22   b  are embedded to an upper surface  261  of the second polymeric layer  26 , such that a lower portion of each of the second hollow structures  22   b  is located in the second polymeric layer  26 , and an upper portion of each of the second hollow structures  22   b  is exposed from the second polymeric layer  26 . In this embodiment, the second hollow structures  22   b  are charged through the above-mentioned electrospray extrusion injection. The second hollow structures  22   b  are sprayed from the spray nozzle to the upper surface  261  of the second polymeric layer  26  before the second polymeric layer  26  is cured. Meanwhile, since the second polymeric layer  26  has not been cured, the second hollow structures  22   b  are embedded to the upper surface  261  of the second polymeric layer  26  due to the gravity thereof. The sizes D of the second hollow structures  22   b  are substantially equal to each other, and the second hollow structures  22   b  are distributed on the upper surface  261  of the second polymeric layer  26  uniformly. The second hollow structures  22   b  may be same as or different from the first hollow structures  22   a . 
     Next, the second polymeric layer  26  is cured or hardened through irradiation of UV light or heating. In this embodiment, the second polymeric layer  26  is cured through irradiation of UV light, and the irradiation time is 1 minute to 1 hour. 
     Referring to  FIG. 11 , the steps in  FIG. 9  and  FIG. 10  are repeated at least once, to form at least one polymeric layer  28  on the second polymeric layer  26 , where the polymeric layers  24 ,  26  and  28  form a polymeric elastomer  30 , and the materials of the polymeric layers  24 ,  26  and  28  may be the same or different. 
     Referring to  FIG. 12 , the carrier  23  is removed, to form a polishing pad  3   a.    
       FIG. 12  is a schematic cross-sectional view of a polishing pad according to another embodiment of the present invention. The polishing pad  3   a  comprises a polymeric elastomer  30  and a plurality of hollow structures  22 ,  22   a ,  22   b . The hollow structures  22 ,  22   a ,  22   b  are uniformly distributed in the polymeric elastomer  30 , and the sizes D of the hollow structures  22 ,  22   a ,  22   b  are substantially equal to each other. In this embodiment, the polymeric elastomer  30  is formed by curing a polymeric resin  20 . The material of the polymeric resin  20  is selected from the group consisting of polyamide resin, polycarbonate, polymethacrylic resin, epoxy resin, phenolic resin, polyurethane resin, vinylbenzene resin and acrylic resin, and the material of the hollow structures  22 ,  22   a ,  22   b  is waterborne polyurethane or acrylic resin. In this embodiment, the material of the polymeric resin  20  is acrylic resin, for example, epoxy acrylate, urethane acrylate, polyester acrylate or polyether acrylate. The material of the hollow structures  22 ,  22   a ,  22   b  is waterborne polyurethane. 
     In this embodiment, each of the hollow structures  22 ,  22   a ,  22   b  is a capsule-like structure, which has a closed space formed by a shell  221 . Preferably, the hollow structures  22 ,  22   a ,  22   b  are spherical. The sizes D of the hollow structures  22 ,  22   a ,  22   b  range from 10 μm to 100 μm, and the size variation between the hollow structures  22 ,  22   a ,  22   b  is within 20%. In this embodiment, the sizes D of the hollow structures  22 ,  22   a ,  22   b  range from 30 μm to 40 μm. 
     In this embodiment, the polymeric elastomer  30  includes a plurality of polymeric layers  24 ,  26 ,  28 . Each two polymeric layers comprise one row of hollow structures, such that one portion of the hollow structure is located in an upper polymeric layer and the other portion of the hollow structure is located in a lower polymeric layer. For example, the first polymeric layer  24  and the second polymeric layer  26  comprise one row of first hollow structures  22   a , such that one portion of the first hollow structure  22   a  is located in an upper polymeric layer (the second polymeric layer  26 ) and the other portion of the first hollow structure  22   a  is located in a lower polymeric layer (the first polymeric layer  24 ). 
     The above embodiments are only intended to describe the principle and the efficacies of the present invention, and are not intended to limit the present invention. Therefore, modifications and variations of the embodiments made by persons skilled in the art do not depart from the spirit of the present invention. The scope of the present invention should fall within the scope as defined in the appended claims.