Composition and method for temporarily fixing solids

Abstract

The present invention relates to a method of temporarily and firmly fixing two solids to each other and to a composition used in the method, which is a method of temporarily fixing, comprising temporarily fixing the two solids to each other with a liquid crystal compound or a composition comprising the liquid crystal compound. This method is used for a method of temporarily fixing a pad for chemical mechanical polishing, for example, to polish a wafer for a semiconductor device fixed on a surface of a base plate, when one solid is a pad for chemical mechanical polishing of a wafer for a semiconductor device and the other is a base plate to fix the pad.

1 . A method of processing a wafer for a semiconductor device, comprising: 
 (1) positioning a liquid crystal compound or a composition comprising the liquid crystal compound between the surface of the wafer for a semiconductor device and the surface of a substrate for fixing the wafer;    (2) fixing the wafer for a semiconductor device on the surface of the substrate by heating at a temperature equal to or higher than the melting point of the liquid crystal compound and cooling until the liquid crystal compound is solidified;    (3) processing the exposed surface of the fixed wafer for a semiconductor device;    (4) separating the wafer for a semiconductor device from the substrate by heating at a temperature equal to or higher than the melting point of the liquid crystal compound; and    (5) cleaning the separated wafer for a semiconductor device with a solvent which dissolves the liquid crystal compound or the composition comprising the liquid crystal compound.    
     
     
         2 . The method according to  claim 1 , wherein the step (1) is carried out by spraying the liquid crystal compound or the composition comprising the liquid crystal compound as a solid powder on the surface of at least one of the wafer for a semiconductor device and the substrate for fixing the wafer, by placing it as a pellet on the surface, or by applying it as a solution containing a solvent to the surface and then removing the solvent.  
     
     
         3 . The method according to  claim 1 , wherein the step (1) is carried out by placing a film of the composition comprising the liquid crystal compound on the surface of at least one of the wafer for a semiconductor device and the substrate for fixing the wafer.  
     
     
         4 . The method according to  claim 1 , wherein the exposed surface of the wafer for a semiconductor device in the step (3) is the rear surface having no semiconductor elements, and the processing is the polishing of the rear surface.  
     
     
         5 . The method according to  claim 4 , wherein the step (3′) of affixing a dicing tape to the polished rear surface of the wafer for a semiconductor device is carried out between the step (3) and the step (4), and the wafer for a semiconductor device is separated from the substrate together with a dicing tape in the step (4).  
     
     
         6 . The method according to  claim 4 , wherein the step (3″) of temporarily fixing an organic polymer film to the polished rear surface of the wafer for a semiconductor device with the liquid crystal compound or the composition comprising the liquid crystal compound is carried out between the step (3) and the step (4), and then the wafer for a semiconductor device is separated from the substrate together with the organic polymer film in the step (4).  
     
     
         7 . The method according to  claim 1 , wherein the wafer for a semiconductor device is separated from the substrate together with a dicing tape (4), the wafer for a semiconductor device is cleaned together with the dicing tape in the step (5), and the step (6) of dicing the wafer for a semiconductor device to which the dicing tape is affixed is further carried out after the step (5).  
     
     
         8 . The method according to  claim 1 , wherein the wafer for a semiconductor device is separated from the substrate together with an organic polymer film in (4), the wafer for a semiconductor device is cleaned while the organic polymer film is fixed thereto in the step (5), and the step (6′) of dicing the wafer for a semiconductor device to which the organic polymer film is fixed is carried out after the step (5).