Method for making integrated semiconductor circuit structure with formation of Ti or Ta silicide

Abstract

The compounds TiSi 2 and TaSi 2 have been found to be suitable substitutes for polysilicon layers in semiconductor integrated circuits. Suitable conducting properties of the compounds are ensured by providing a relatively thin substrate of polysilicon.

We claim: 
     
       1. A method for making a semiconductor device from a wafer including a silicon .[.epitaxial surface.]. layer, said method comprising the steps of heating the wafer in an oxidizing atmosphere for a time and at a temperature for forming a first SiO 2  overlay, forming a first layer of doped polysilicon over said SiO 2  layer, .[.depositing.]. .Iadd.forming .Iaddend.on said polysilicon layer .Iadd.in a sintering step .Iaddend.a second layer of a .[.material.]. .Iadd.silicide .Iaddend.selected from the group consisting of .[.Ti and Ta sintering the material of said second layer at a temperature and for a time to form a silicide.]. TiSi 2  and TaSi 2  .[.of the material, respectively,.]. .Iadd.in a manner to avoid the formation of an oxide layer thereover, .Iaddend.heating the wafer for a time and at a temperature to form a second SiO 2  overlay while leaving a layer of polysilicon in excess of 1000 Angstroms therebeneath, etching a pattern in said second SiO 2  overlay, depositing an electrically-conducting material over said second SiO 2  overlay, and etching a pattern in said electrically-conducting material. 
     
     
       2. A method in accordance with claim 1 in which said second layer comprises Ti and is sintered at about 900 degrees C. and heated in an oxygen atmosphere. 
     
     
       3. A method in accordance with claim 1 in which said second layer comprises Ta and is sintered at at least about 1000 degrees C. and is heated in steam.