Method of forming ohmic contact to a semiconductor body

Abstract

A process for forming an ohmic contact on the back surface of a semiconductor body includes depositing a donor layer on the back surface of the semiconductor body followed by a sintering step to form a shallow intermetallic region capable of forming a low resistance contact with a contact metal.

1 . A semiconductor device, comprising:
 a float zone silicon substrate having N type conductivity, said substrate having a top surface and a back surface;   a plurality of PiN diodes and Schottky contacts formed within said top surface of said substrate along an active region;   an intermetallic region of low contact resistivity in said back surface of said substrate; and   a contact metal in contact with said intermetallic region forming an ohmic contact.   
   
   
       2 . The semiconductor device of  claim 1 , wherein said device has a thickness of 75 cm or less. 
   
   
       3 . The semiconductor device of  claim 1 , wherein said intermetallic region has a depth of approximately 0.5 to 1.6 μm. 
   
   
       4 . The semiconductor device of  claim 1 , wherein said intermetallic region includes either AuAs atoms, AuSb atoms, or AuSn atoms 
   
   
       5 . The semiconductor device of  claim 4 , further comprising:
 a plurality of spaced field oxide rings atop said upper surface of said substrate along a termination region;   a plurality of guard rings of P type conductivity within said upper surface of said substrate, each guard ring being between adjacent field oxide rings;   a gapped oxide layer atop said upper surface of said substrate and between adjacent field oxide rings, each gapped oxide layer exposing an underlying guard ring; and   separate stepped field plates over each of said field oxide rings, wherein each field plate contacts either an anode contact metal or one of said guard rings through one of said gapped oxide layers.