Method of forming predominantly <100> polycrystalline silicon thin film transistors

Abstract

A method is provided to produce thin film transistors (TFTs) on polycrystalline films having a single predominant crystal orientation. A layer of amorphous silicon is deposited over a substrate to a thickness suitable for producing a desired crystal orientation. Lateral-seeded excimer laser annealing (LS-ELA) is used to crystallize the amorphous silicon to form a film with a preferred crystal orientation. A gate is formed overlying the polycrystalline film. The polycrystalline film is doped to produce source and drain regions.

What is claimed is:  
     
         1 . A method of forming thin film transistor (TFT) structures on a substrate comprising the steps of; 
 a) providing the substrate;    b) depositing an amorphous silicon film at least 100 nm thick over the substrate;    c) annealing the amorphous silicon film using a lateral crystallization process to produce a polycrystalline film having a predominantly < 100 > crystallographic orientation;    d) forming a gate structures over the polycrystalline film; and    e) doping the polycrystalline film having a predominantly < 100 > crystallographic orientation to produce source regions and drain regions.    
     
     
         2 . The method of  claim 1;  wherein the substrate is transparent.  
     
     
         3 . The method of  claim 2 , wherein the substrate is quartz, glass or plastic.  
     
     
         4 . The method of  claim 1 , wherein the amorphous silicon film is in the range of between approximately 100 and 250 nm thick.  
     
     
         5 . The method of  claim 1 , wherein the polycrystalline film has a crystallographic orientation within 15 degrees of < 100 >.  
     
     
         6 . The method of  claim 1 , wherein the polycrystalline film has a crystallographic orientation within 10 degrees of < 100 >.  
     
     
         7 . The method of  claim 1 , wherein the lateral crystallization process comprises a sequence of laser pulses projected through a mask having a narrow slit to project a beamlet onto the surface of the amorphous silicon film to crystallize the amorphous silicon film as the beamlet is advanced over the surface of the amorphous silicon film between successive laser pulses.  
     
     
         8 . A thin film transistor (TFT) structure comprising: 
 a) a substrate;    b) a polycrystalline silicon film having a predominantly < 100 > crystallographic orientation overlying the substrate;    c) a gate structure formed over the polycrystalline silicon film; and    d) source and drain regions formed by doping the polycrystalline silicon film.    
     
     
         9 . The thin film transistor structure of  claim 8 , wherein the substrate is transparent.  
     
     
         10 . The thin film transistor structure of  claim 9 , wherein the substrate is quartz, glass, or plastic.  
     
     
         11 . The thin film transistor structure of  claim 8 , wherein the polycrystalline silicon film is at least 100 nm thick.  
     
     
         12 . The thin film transistor structure of  claim 8 , wherein the polycrystalline silicon film is in the range of between approximately 100 and 250 nm thick.  
     
     
         13 . The thin film transistor structure of  claim 8 , wherein the source and drain regions extend only partially through the polycrystalline silicon film.