Method of removal profile modulation in cmp pads

Abstract

A polishing pad includes a plurality of polishing surfaces, a first group of the polishing surfaces made of a first material having a first coefficient of friction and a second group of the polishing surfaces made of a second material having a second coefficient of friction. The first and second groups of polishing surfaces may be arranged over the polishing pad so as to provide a non-planar material removal profile. The polishing surface layout may be designed by evaluating a material removal profile for an existing polishing pad of known characteristics, observing how variations in polishing surface densities and/or coefficients of friction affect that material removal profile, and then mapping the polishing surface coefficients of friction and density profiles to the subject polishing pad layout.

1 . A polishing pad, comprising a plurality of polishing surfaces, a first group of the polishing surfaces made of a first material having a first coefficient of friction and a second group of the polishing surfaces made of a second material having a second coefficient of friction, the first and second groups of polishing surfaces arranged over the polishing pad so as to provide a non-planar material removal profile. 
     
     
         2 . The polishing pad of  claim 1 , wherein the first and second groups of polishing surfaces are arranged to provide an edge fast material removal profile. 
     
     
         3 . The polishing pad of  claim 1 , wherein the first and second groups of polishing surfaces are arranged to provide an edge slow removal profile. 
     
     
         4 . The polishing pad of  claim 1 , wherein the first and second groups of polishing surfaces are arranged to provide a center fast removal profile. 
     
     
         5 . The polishing pad of  claim 1  wherein the first and second groups of polishing surfaces are arranged to provide a center slow removal profile. 
     
     
         6 . The polishing pad of  claim 1 , wherein the polishing surfaces comprise individual polishing elements, each polishing element supported by an underlying compressible foam layer and oriented with a long axis normal to a plane defined by the underlying compressible foam layer. 
     
     
         7 . The polishing pad of  claim 6 , wherein the polishing elements are spaced apart from one another so that displacement of one polishing element along its long axis in a direction normal to the plane defined by the underlying foam layer does not materially affect displacement of adjacent ones of the polishing elements. 
     
     
         8 . The polishing pad of  claim 1 , wherein the polishing elements of the first group are made of polyurethane and the polishing elements of the second groups are made of polyoxymethylene. 
     
     
         9 . The polishing pad of  claim 1 , wherein the first and second groups of polishing surfaces are arranged in different densities over the polishing pad. 
     
     
         10 . The polishing pad of  claim 9 , wherein the different densities vary by radial distance of the polishing surfaces from a center of the polishing pad. 
     
     
         11 . The polishing pad of  claim 9 , wherein the different densities vary orthogonally across the polishing pad. 
     
     
         12 . The polishing pad of  claim 9 , wherein polishing surface density variations are implemented by varying groove pitch over the polishing pad. 
     
     
         13 . The polishing pad of  claim 9 , wherein polishing surface density variations are implemented by varying groove size over the polishing pad. 
     
     
         14 . The polishing pad of  claim 1 , wherein overall densities of polishing surfaces per unit area of the polishing pad is uniform for the polishing pad. 
     
     
         15 . The polishing pad of  claim 1 , wherein the first and second groups of polishing surfaces are laid out in uniform radial arrangement over the entire polishing pad. 
     
     
         16 . The polishing pad of  claim 1 , wherein each polishing surface of the first and second groups has a common size. 
     
     
         17 . The polishing pad of  claim 1 , wherein each polishing surface of the first and second groups has a common shape. 
     
     
         18 . The polishing pad of  claim 1 , wherein the polishing surfaces comprise individual polishing elements laid out in an orthogonal arrangement where inter-polishing element spacing is defined by a pitch in each of two dimensions. 
     
     
         19 . The polishing pad of  claim 18 , wherein the inter-polishing element pitch in at least one of the two dimensions varies across the polishing pad. 
     
     
         20 . The polishing pad of  claim 18 , wherein the inter-polishing element pitch in both of the two dimensions varies across the polishing pad. 
     
     
         21 . The polishing pad of  claim 1 , wherein the polishing surfaces comprise individual polishing elements laid out in a radial pattern such that polishing elements at different radial distances from a center of the polishing pad have different inter-polishing element spacing. 
     
     
         22 . A method, comprising polishing a workpiece using a polishing pad defined by any one of the preceding claims. 
     
     
         23 . A method, comprising designing a layout of polishing surfaces for a polishing pad to achieve a desired material removal profile for the polishing pad by (a) determining a first material removal profile of a first polishing pad having a known polishing surface layout, (b) applying polishing surface coefficient of friction variations and/or polishing surface density variations corresponding to regions of the first polishing pad where changes in the first material removal profile are desired, (c) determining what fraction of a total polishing time is spent by an area of a wafer of interest in the regions of the first pad, (d) determining, based on these fractional times, corresponding variations in the first material removal profile at pad-wafer locations of interest, and (e) determining the new pad layout to achieve the desired material removal profile by mapping new polishing surface coefficients of friction and density profiles to the subject polishing pad layout.