Polishing pad, method of manufacturing the polishing pad, and chemical mechanical polishing apparatus comprising the polishing pad

Abstract

A polishing pad of a CMP apparatus has a plurality of pores. A characteristic associated with the pores, such as average size or pore density, varies substantially from region to region of the pad across the pad in a diametral direction of the pad. The polishing pad can be designed and manufactured using sample pads whose pore characteristics differ from each other. CMP test processes are performed in which the sample pads are used to polish test wafers, and the rates at which the test wafers are polished are measured and stored in a database. The polishing pad is fabricated using data from the database so that a chemical mechanical polishing apparatus employing the pad will polish wafers with a high degree of uniformity. The database can be used to select sample pads from a stockpile. Sections of the sample pads are cut out, respectively, and fastened to one another.

1 . A chemical mechanical polishing apparatus comprising: 
 a platen supported in the apparatus so as to be rotatable;    a dispensing system that dispenses a polishing medium;    a polishing pad disposed on the upper surface of and attached to the platen to receive the polishing medium dispensed by the dispensing system, the polishing pad having a plurality of pores some of which are isolated inside the polishing pad and others of which are exposed at an upper surface of the polishing pad to confine the polishing medium to the pad,    wherein a characteristic associated with the pores varies substantially from region to region of the pad across the pad in a diametral direction of the pad, thereby demarcating the regions from one another; and    a polishing head having a chuck that holds a substrate to be polished and is movable in the apparatus to press a surface of a substrate held by the chuck against the polishing pad.    
     
     
         2 . The chemical mechanical polishing apparatus of  claim 1 , wherein said characteristic associated with the pores is either the average size of the pores within the polishing pad or the pore density, the pore density corresponding to the ratio of the volume of all of the pores located in a region of the pad to the total volume of that region.  
     
     
         3 . The chemical mechanical polishing apparatus of  claim 1 , wherein said characteristic associated with the pores is the average size of the pores within the polishing pad, whereby the average size of the pores within each of said regions varies from region to region across the pad in the diametral direction of the pad.  
     
     
         4 . The chemical mechanical polishing apparatus of  claim 1 , wherein said characteristic associated with the pores is the pore density, whereby the pore density varies from region to region across the pad in the diametral direction of the pad.  
     
     
         5 . The chemical mechanical polishing apparatus of  claim 2 , wherein the polishing pad has an inner section at a central region of the pad, and an outer section that is disposed radially outwardly of the inner section, said characteristic of the outer section of the pad being different from said characteristic of the inner section of the pad.  
     
     
         6 . The chemical mechanical polishing apparatus of  claim 5 , wherein the inner section of the pad is circular, and the outer section of the pad is annular.  
     
     
         7 . The chemical mechanical polishing apparatus of  claim 2 , wherein the polishing pad has a plurality of sections that are adjacent one another including an inner section at a central region of the pad, and a plurality of outer sections that are disposed radially outwardly of the inner section, and said characteristic of each of the sections of the pad is different from that of the section adjacent thereto.  
     
     
         8 . The chemical mechanical polishing apparatus of  claim 7 , wherein the inner section of the pad is circular and each of the outer sections of the pad is annular.  
     
     
         9 . The chemical mechanical polishing apparatus of  claim 2 , wherein the polishing pad has an upper portion that includes the upper surface at which pores of the pad are exposed, and a lower portion interposed between the upper portion and said platen, wherein said characteristic varies substantially from region to region of the upper portion of the pad across the pad in a diametral direction of the pad, thereby demarcating the regions of the upper portion of the pad from one another.  
     
     
         10 . The chemical mechanical polishing apparatus of  claim 2 , wherein the polishing pad has an upper portion that includes the upper surface at which pores of the pad are exposed, and a lower portion interposed between the upper portion and said platen, wherein said characteristic varies substantially from region to region of the lower portion of the pad across the pad in a diametral direction of the pad, thereby demarcating the regions of the lower portion of the pad from one another.  
     
     
         11 . The chemical mechanical polishing apparatus of  claim 2 , wherein the polishing head is movable in the apparatus to a polishing position at which the center of a surface of a substrate held by the chuck is disposed on the polishing pad at a location spaced a predetermined distance from the center of the polishing pad, 
 the polishing pad has first and second sections dedicated to contact a peripheral area of a substrate held by the polishing head at the polishing position during a polishing process, and an intermediate section dedicated to contact a central region of the substrate held by the polishing head at the polishing position during the polishing process, and    said characteristic of the first section of the pad and said characteristic of said second section of the pad are each different from said characteristic of the intermediate section of the pad.    
     
     
         12 . The chemical mechanical polishing apparatus of  claim 2 , wherein the polishing head is movable in the apparatus to a polishing position at which the center of a surface of a substrate held by the chuck is disposed on the polishing pad at the center of the polishing pad, 
 the polishing pad has a peripheral section dedicated to contact a peripheral area of a substrate held by the polishing head at the polishing position during a polishing process, and a central section dedicated to contact a central area of the substrate held by the polishing head at the polishing position during the polishing process, and    said characteristic of the peripheral section of the pad is different from that of the central section of the pad.    
     
     
         13 . The chemical mechanical polishing apparatus of  claim 1 , wherein said characteristic is the spacing of the pores, whereby the spacing of the pores varies substantially from region to region of the pad across the pad in a diametral direction of the pad.  
     
     
         14 . The chemical mechanical polishing apparatus of  claim 4 , wherein the pore density of a peripheral region of the polishing pad less than the pore density of a central region of the polishing pad.  
     
     
         15 . The chemical mechanical polishing apparatus of  claim 4 , wherein the pore density of a peripheral region of the polishing pad is greater than the pore density of a central region of the polishing pad.  
     
     
         16 . A polishing pad of a chemical mechanical polishing apparatus, the polishing pad having a plurality of pores some of which are isolated inside the polishing pad and others of which are exposed at an upper surface of the polishing pad to confine a polishing medium to the pad, 
 wherein a characteristic associated with the pores varies substantially from region to region of the pad across the pad in a diametral direction of the pad, thereby demarcating the regions from one another.    
     
     
         17 . The polishing pad of  claim 16 , wherein said characteristic associated with the pores is either the average size of the pores within the polishing pad or the pore density, the pore density corresponding to the ratio of the volume of all of the pores located in a region of the pad to the total volume of that region.  
     
     
         18 . The polishing pad of  claim 16 , wherein said characteristic associated with the pores is the average size of the pores within the polishing pad, whereby the average size of the pores within each of said regions varies from region to region across the pad in the diametral direction of the pad.  
     
     
         19 . The polishing pad of  claim 16 , wherein said characteristic associated with the pores is the pore density, whereby the pore density varies from region to region across the pad in the diametral direction of the pad.  
     
     
         20 . The polishing pad of  claim 17 , wherein the polishing pad has an inner section at a central region of the pad, and an outer section that is disposed radially outwardly of the inner section, said characteristic of the outer section of the pad being different from said characteristic of the inner section of the pad.  
     
     
         21 . The polishing pad of  claim 20 , wherein the inner section of the pad is circular, and the outer section of the pad is annular.  
     
     
         22 . The polishing pad of  claim 17 , wherein the polishing pad has a plurality of sections that are adjacent one another including an inner section at a central region of the pad, and a plurality of outer sections that are disposed radially outwardly of the inner section, and said characteristic of each of the sections of the pad is different from that of the section adjacent thereto.  
     
     
         23 . The polishing pad of  claim 22 , wherein the inner section of the pad is circular and each of the outer sections of the pad is annular.  
     
     
         24 . The polishing pad of  claim 17 , wherein the polishing pad has an upper portion that includes the upper surface at which pores of the pad are exposed, and a lower portion interposed between the upper portion and said platen, wherein said characteristic varies substantially from region to region of the upper portion of the pad across the pad in a diametral direction of the pad, thereby demarcating the regions of the upper portion of the pad from one another.  
     
     
         25 . The polishing pad of  claim 17 , wherein the polishing pad has an upper portion that includes the upper surface at which pores of the pad are exposed, and a lower portion interposed between the upper portion and said platen, wherein said characteristic varies substantially from region to region of the lower portion of the pad across the pad in a diametral direction of the pad, thereby demarcating the regions of the lower portion of the pad from one another.  
     
     
         26 . The polishing pad of  claim 16 , wherein said characteristic is the spacing of the pores, whereby the spacing of the pores varies substantially from region to region of the pad across the pad in a diametral direction of the pad.  
     
     
         27 . The polishing pad of  claim 19 , wherein the pore density of a peripheral region of the polishing pad less than the pore density of a central region of the polishing pad.  
     
     
         28 . The polishing pad of  claim 19 , wherein the pore density of a peripheral region of the polishing pad is greater than the pore density of a central region of the polishing pad.  
     
     
         29 . A method of manufacturing a polishing pad of a chemical mechanical polishing (CMP) apparatus, comprising: 
 providing sample pads each having a characteristic that influences the rate at which the sample pad can be used to polish a film of material in a CMP process;    performing CMP test processes using the sample pads on a plurality of substrates each having a film of material thereon to thereby polish the films, measuring the rates at which the films are polished using the sample pads, and constructing a database in which measurements of the rates at which the films were polished are correlated to said characteristics of the sample pads used to effect said rates;    predetermining rates at which each of several regions of a semiconductor wafer are to be polished using an actual CMP process;    designing a polishing pad by using the database to assign said characteristics in the database to sections of the polishing pad that will polish said several regions of the semiconductor wafer, respectively, when the polishing pad is used in the actual CMP process; and    fabricating a polishing pad in which the sections of the pad have the characteristics assigned thereto.    
     
     
         30 . The method of  claim 29 , wherein each of the sections of the polishing pad to which said characteristics are assigned is a circular or annular section.  
     
     
         31 . The method of  claim 29 , wherein the rate at which a film is polished using each of the sample pads is measured at multiple locations across the substrate on which the film is disposed, and each of said measurements in the database is data of a profile of the rate across the substrate.  
     
     
         32 . The method of  claim 29 , wherein the rate at which a film is polished using each of the sample pads is measured at multiple locations across the substrate on which the film is disposed, and each of said measurements in the database is data of an average of the rates measured at said locations across the substrate.  
     
     
         33 . The method of  claim 29 , wherein the characteristic is the average size of the pores within the sample pad or the pore density, the pore density corresponding to the ratio of the volume of all of the pores located in a region of the sample pad to the total volume of that region.  
     
     
         34 . The method of  claim 29 , wherein the fabricating of the polishing pad comprises cutting out sections from several sample pads, and fastening the sections cut out from the sample pads to one another.  
     
     
         35 . A method of manufacturing a polishing pad of a chemical mechanical polishing (CMP) apparatus, the method comprising: 
 providing several sample pads each having a plurality of pores some of which are isolated inside the sample pad and others of which are exposed at an upper surface of the sample pad to confine the polishing medium to the pad, and a characteristic associated with the pores that influences that the rate at which the sample pad can be used in a CMP process to polish a wafer,    wherein said characteristics of the sample pads are different from each other such that the sample pads if used in carrying out the CMP process on similar wafers, respectively, would polish the similar wafers at different rates;    cutting out sections from the sample pads, respectively; and    fastening the sections to one another in such a way as to fabricate a polishing pad in which the characteristic varies.    
     
     
         36 . The method of  claim 35 , wherein the characteristic associated with the pores is either the average size of the pores within the sample pad or the pore density, the pore density corresponding to the ratio of the volume of all of the pores located in a region of the pad to the total volume of that region.  
     
     
         37 . The method of  claim 35 , wherein said cutting comprises cutting out a circular section from one of the sample pads and an annular section from another of the sample pads.