Method of manufacturing a semiconductor device having a trench isolation structure

Abstract

In a method of manufacturing a semiconductor device, a silicon oxide film is embedded in a trench portion for isolating the device forming regions on a silicon substrate, and a silicon nitride film, a polysilicon film, and a pad insulating film left on the device forming regions on a silicon substrate are removed to expose a surface of the semiconductor substrate, wherein the polysilicon film is removed by isotropic wet etching.

1 . A method of manufacturing a semiconductor device, comprising the steps of: 
 forming a pad insulating film, a polysilicon film, and a silicon nitride film sequentially on a semiconductor substrate;    forming a trench portion for isolating device forming regions on said semiconductor substrate by selectively etching said silicon nitride film, polysilicon film, pad insulating film, and semiconductor substrate;    embedding a silicon oxide film in said trench portion for isolating said device forming regions;    removing said silicon nitride film, polysilicon film, and pad insulating film to expose a surface of said semiconductor substrate; and    forming a circuit element on the exposed surface of said semiconductor substrate; wherein said polysilicon film is removed by isotropic wet etching.    
     
     
         2 . The method of manufacturing a semiconductor device according to  claim 1 , wherein a heat treatment to said silicon oxide film embedded in said trench portion is performed at a temperature of 1,050° C.  
     
     
         3 . The method of manufacturing a semiconductor device according to  claim 1 , wherein said wet etching is performed by aqueous ammonia or a mixed solution of aqueous ammonia and a hydrogen peroxide solution.  
     
     
         4 . The method of manufacturing a semiconductor device according to  claim 1 , wherein a CVD oxide film is formed on said silicon oxide film embedded in said trench portion, following the step of removing said silicon nitride film and polysilicon film.  
     
     
         5 . The method of manufacturing a semiconductor device according to  claim 1 , wherein said silicon oxide film embedded in said trench portion is oxidized, following the step of removing said silicon nitride film and polysilicon film.  
     
     
         6 . The method of manufacturing a semiconductor device according to  claim 1 , wherein a short-time, rapid heat treatment is performed on said silicon oxide film embedded in said trench portion, following the step of removing said silicon nitride film and polysilicon film.  
     
     
         7 . The method of manufacturing a semiconductor device according to  claim 1 , wherein said pad insulating film is removed by use of a hydrofluoric acid solution followed by a treatment with a phosphoric acid type solution, to expose a surface of said semiconductor substrate.  
     
     
         8 . The method of manufacturing a semiconductor device according to  claim 1 , 
 wherein the step of removing said pat insulating film includes the sub steps of: 
 removing only thin portions of said pad insulating film to partially expose a surface of said semiconductor substrate;  
 performing a wet treatment to remove a nitride layer from said surface of said semiconductor substrate; and  
 then removing remaining portions of said pad insulating film to expose a surface of said semiconductor substrate.  
   
     
     
         9 . The method of manufacturing a semiconductor device according to  claim 1 , wherein ion implantation into said semiconductor substrate is performed after removing said silicon nitride film and polysilicon film, and prior to removing said pad insulating film.  
     
     
         10 . The method of manufacturing a semiconductor device according to  claim 1 , wherein said step of forming a circuit element on the exposed surface of said semiconductor substrate includes the sub-steps of: 
 forming at least a gate insulating film, a polysilicon film, and an upper insulating film sequentially on said exposed surface of said semiconductor substrate;    forming agate electrode by patterning said upper insulating film, polysilicon film, and gate insulating film by anisotropic etching; and    performing isotropic wet etching to remove polysilicon on said surface of said semiconductor substrate.    
     
     
         11 . A method of manufacturing a semiconductor device, comprising the steps of: 
 forming a pad insulating film, and a silicon nitride film sequentially on a semiconductor substrate;    forming a trench portion for isolating device forming regions on said semiconductor substrate by selectively etching said silicon nitride film, pad insulating film, and semiconductor substrate;    embedding a silicon oxide film in said trench portion for isolating said device forming regions;    removing said silicon nitride film, and pad insulating film to expose a surface of said semiconductor substrate; and    forming a circuit element on the exposed surface of said semiconductor substrate.    
     
     
         12 . The method of manufacturing a semiconductor device according to  claim 11 , wherein a CVD oxide film is formed on said silicon oxide film embedded in said trench portion, following the step of removing said silicon nitride film.  
     
     
         13 . The method of manufacturing a semiconductor device according to  claim 11 , wherein said silicon oxide film embedded in said trench portion is oxidized, following the step of removing said silicon nitride film.  
     
     
         14 . The method of manufacturing a semiconductor device according to  claim 11 , wherein a short-time, rapid heat treatment is performed on said silicon oxide film embedded in said trench portion, following the step of removing said silicon nitride film.  
     
     
         15 . The method of manufacturing a semiconductor device according to  claim 11 , wherein said pad insulating film is removed by use of a hydrofluoric acid solution followed by a treatment with a phosphoric acid type solution, to expose a surface of said semiconductor substrate.  
     
     
         16 . The method of manufacturing a semiconductor device according to  claim 11 , wherein the step of removing said pat insulating film includes the sub steps of: 
 removing only thin portions of said pad insulating film to partially expose a surface of said semiconductor substrate;    performing a wet treatment to remove a nitride layer from said surface of said semiconductor substrate; and    then removing remaining portions of said pad insulating film to expose a surface of said semiconductor substrate.    
     
     
         17 . The method of manufacturing a semiconductor device according to  claim 11 , wherein ion implantation into said semiconductor substrate is performed after removing said silicon nitride film, and prior to removing said pad insulating film.  
     
     
         18 . The method of manufacturing a semiconductor device according to  claim 11 , wherein said step of forming a circuit element on the exposed surface of said semiconductor substrate includes the sub-steps of: 
 forming at least a gate insulating film, a polysilicon film, and an upper insulating film sequentially on said exposed surface of said semiconductor substrate;    forming a gate electrode by patterning said upper insulating film, polysilicon film, and gate insulating film by anisotropic etching; and    performing isotropic wet etching to remove polysilicon on said surface of said semiconductor substrate.    
     
     
         19 . The method of manufacturing a semiconductor device according to  claim 18 , wherein said gate electrode is formed by patterning said upper insulating film and a top layer portion of said polysilicon film by anisotropic etching and then patterning a remaining portion of said polysilicon film and said pad insulating film by isotropic wet etching.  
     
     
         20 . A method of manufacturing a semiconductor device, comprising the steps of: 
 forming a storage node on an interlayer insulating film that is formed on a semiconductor substrate;    roughening a surface of said storage node; and    wet-etching a surface of said interlayer insulating film.