Uv curable cmp polishing pad and method of manufacture

Abstract

A method of fabricating a chemical mechanical polishing pad includes introducing polymer precursors containing acrylate functional groups into a mold, providing abrasive particles and a photo-initiator in the polymer precursors to form a mixture, and while the mixture is contained between a bottom plate and a top cover of the mold, exposing the mixture to ultraviolet radiation through a transparent section of the mold to cause the polymer precursors to form radicals, forming a polymer matrix from the polymer precursor by causing the radicals to cross-link with one another. The polishing layer includes the polymer matrix having the abrasive particles dispersed therein.

What is claimed is: 
     
         1 . A method of fabricating a chemical mechanical polishing pad, comprising:
 introducing into a mold a mixture including a polymer precursor containing an acrylate functional group and a photo-initiator such that the mixture covers a flat bottom plate of the mold; and   while the mixture is contained between the bottom plate and a flat top cover of the mold, exposing the mixture to ultraviolet radiation through a flat transparent section of flat top cover of the mold such that the photo-initiator creates initial radicals that attack the acrylate functional group to generate acrylate radicals and the acrylate radicals cross-link to form a polymer matrix that provides a polishing layer of the polishing pad.   
     
     
         2 . The method of  claim 1 , wherein the photo-initiator comprises a reactive acrylate monomer. 
     
     
         3 . The method of  claim 2 , wherein the polymer precursor comprises an acrylate oligomer. 
     
     
         4 . The method of  claim 2 , wherein the polymer precursor comprises polyurethane acrylate, polyester acrylate or polyether acrylate. 
     
     
         5 . The method of  claim 1 , wherein the photo-initiator has a lower viscosity than the polymer precursor. 
     
     
         6 . The method of  claim 1 , further comprising mixing of the polymer precursor and the photo-initiator in the presence of a gas, the mixing performed at sufficient rapidity to generate gas bubbles in the mixture, and immediately exposing the mixture to the ultraviolet radiation to trap the gas bubbles in the polishing layer. 
     
     
         7 . The method of  claim 1 , further comprising introducing bubbles of gas to the polymer precursor prior to mixing the polymer precursor and the photo-initiator, and exposing the mixture to radiation immediately after mixing the polymer precursor. 
     
     
         8 . The method of  claim 1 , further comprising introducing porogens to the mixture before exposing the mixture to the ultraviolet radiation to provide pores in the polishing layer. 
     
     
         9 . The method of  claim 1 , wherein the polymer precursor containing acrylate functional groups comprises an acrylate oligomer, or a reactive acrylate monomer, wherein cross-linking occurs between unsaturated carbon-carbon bonds in the acrylate oligomers or reactive acrylate monomer. 
     
     
         10 . The method of  claim 1 , wherein exposing the mixture to ultraviolet radiation comprises exposing the mixture first to ultraviolet radiation in a first wavelength band, and then exposing the mixture to ultraviolet radiation in a second wavelength band having wavelengths shorter than the first wavelength band. 
     
     
         11 . The method of  claim 1 , wherein the mixture includes a thermal initiator and the mixture is subjected to temperature sufficient to activate the thermal initiator. 
     
     
         12 . The method of  claim 1 , wherein exposing the mixture to ultraviolet radiation cures an entire thickness of the polishing layer. 
     
     
         13 . The method of  claim 12 , wherein the bottom plate contacts a polishing surface of the polishing layer and the top cover contacts a bottom surface of the polishing layer. 
     
     
         14 . A system, comprising:
 a conveyor belt having a width;   a mold having a flat bottom plate and a flat top cover, the mold configured to hold a mixture including a polymer precursor and a photo-initiator between the flat bottom plate and the flat top cover, the mold configured to be supported and transported by the conveyor belt, the mold having a width smaller than the width of the conveyor belt, the top cover of the mold having an ultraviolet (UV) transparent section;   a dispenser to dispense the mixture into the mold; and   an array UV of radiation sources mounted across the width of the conveyor belt, the array of UV radiation sources positioned for UV radiation from the array of radiation sources to pass through the UV transparent section to cure the mixture in the mold to form an entire thickness of a polishing layer.   
     
     
         15 . The system of  claim 14 , wherein the array of UV radiation sources comprises an array of gallium doped (V) bulbs in front of an array of iron doped (D) bulbs, along a direction of travel of the conveyor belt. 
     
     
         16 . The system of  claim 14 , wherein the array of UV radiation sources comprises a first array of UV light sources to expose the mixture first to ultraviolet radiation in a first wavelength band, and a second array of UV light sources to expose the mixture to ultraviolet radiation in a second wavelength band having wavelengths shorter than the first wavelength band. 
     
     
         17 . The system of  claim 16 , wherein the first array of UV light sources is positioned before the second array of UV light sources along a direction of travel of the conveyor belt. 
     
     
         18 . The system of  claim 14 , further comprising an array of infrared (IR) light sources.