Ex parte IWAMURO - Page 7

          Appeal No. 95-4159                                                          
          Application 08/151,055                                                      

          whereas the typical PT IGBT has life-time-killers in the                    
          Although the examiner proposes to use Laska to teach                        
          nothing more than the fact that the P- and/or P+ layers of Fay              
          could be created by using a doping technique, this position                 
          ignores specific language of claim 1 which Fay cannot meet.                 
          The examiner reads the substrate of claim 1 on layers 13 and                
          14 of Fay which are epitaxially grown layers of N-doped                     
          silicon.  The examiner asserts that one can look to the                     
          average concentration of layers 13 and 14 and consider it as a              
          single substrate layer of that concentration.  However,                     
          replacing layers 13 and 14 in Fay with a single layer having                
          the average concentration would destroy the Fay device.  The                
          heavily doped layer 13 is necessary in Fay to provide a buffer              
          layer between the N-type epitaxial layer and the lightly doped              
          P-type layer so the device can operate as a PT IGBT.                        
          Claim 1 also recites that the substrate is “produced                        
          from a single silicon crystal prepared by a zone melting                    
          method and substantially free of lifetime killers.”  We fail                
          to see how the epitaxially grown layers of Fay can meet this                
          recitation.  As noted above, the PT IGBT of Fay would be                    

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Last modified: November 3, 2007