Semiconductor substrate with semi-insulating polysilicon gettering site layer and process of fabrication thereof

Abstract

A semi-insulating polycrystalline silicon layer containing oxygen of at least 10 percent by atom is grown on a back surface of a single crystalline silicon wafer, and achieves high gettering efficiency at a thickness less than the thickness of usual polycrystalline silicon so that the silicon substrate is less warped.

What is claimed is:  
     
         1 . A semiconductor substrate used for fabrication of a semiconductor device, comprising: 
 an active layer formed of single crystalline semiconductor material and having a first surface used for fabricating at least one electric component thereon and a second surface reverse to said first surface; and    a gettering site layer grown on said second surface of said active layer, and formed of semi-insulating polycrystalline silicon containing oxygen of at least 10 percent by atom.    
     
     
         2 . The semiconductor substrate as set forth in    claim 1   , in which said active layer is formed of single crystalline silicon.  
     
     
         3 . The semiconductor substrate as set forth in    claim 1   , in which said active layer is formed of single crystalline silicon, and boron is doped into the semi-insulating polycrystalline silicon.  
     
     
         4 . The semiconductor substrate as set forth in    claim 1   , in which said active layer is formed of single crystalline silicon, and phosphorous is doped into the semi-insulating polycrystalline silicon.  
     
     
         5 . The semiconductor substrate as set forth in    claim 1   , in which said gettering site layer is less than 1.2 microns thick.  
     
     
         6 . A process of producing a semiconductor substrate used for a semiconductor device, comprising the steps of: 
 a) preparing an active layer of single crystalline semiconductor material; and    b) forming a gettering site layer formed of semi-insulating polycrystalline silicon containing oxygen of at least 10 percent by atom on one surface of said active layer.    
     
     
         7 . The process as set forth in    claim 6   , in which said single crystalline semiconductor material is single crystalline silicon.  
     
     
         8 . The process as set forth in    claim 6   , in which said single crystalline semiconductor layer is formed of single crystalline silicon, and boron is doped into the semi-insulating polycrystalline silicon.  
     
     
         9 . The process as set forth in    claim 8   , in which said boron is introduced in said semi-insulating polycrystalline silicon during a growth in said step b).  
     
     
         10 . The process as set forth in    claim 6   , in which said single crystalline semiconductor layer is formed of single crystalline silicon, and phosphorous is doped into the semi-insulating polycrystalline silicon.  
     
     
         11 . The process as set forth in    claim 10   , in which said phosphorous is introduced in said semi-insulating polycrystalline silicon during a growth in said step b).  
     
     
         12 . The process as set forth in    claim 6   , in which said semi-insulating polycrystalline silicon layer is grown to a certain thickness less than 1.2 microns.