Silison film for thin film transistors

Abstract

A method has been provided for forming a polycrystalline silicon (p-Si) film with a small amount of hydrogen. Such a film has been found to have excellent sheet resistance, and it is useful in the fabrication of liquid crystal display (LCD) panels made from thin film transistors (TFTs). The low hydrogen content polycrystalline silicon films are made from introducing a small amount of hydrogen gas, with Ar, during the sputter deposition of an amorphous silicon film. The hydrogen content in the film is regulated by controlling the deposition temperatures and the volume of hydrogen in the gas feed during the sputter deposition. The polycrystalline silicon film results from annealing the low hydrogen content amorphous silicon film thus formed.

1 . In an integrated circuit (IC) fabrication process, a method for forming a polycrystalline silicon (p-Si) film, the method comprising: 
 sputtering amorphous silicon (a-Si) material on a substrate;    supplying a gas mixture including a hydrogen content of no more than 4% volume in the gas feed; and    forming an amorphous silicon film incorporating hydrogen.    
   
   
       2 . The method of  claim 1  further comprising: 
 annealing the amorphous silicon film; and    forming a polycrystalline silicon film having a crystalline content in the range from 95% to 100% and a hydrogen content in the range from 1 percent by atomic weight (at %) to 3 at %.    
   
   
       3 . The method of  claim 1  wherein sputtering amorphous silicon material on a substrate includes setting the process temperature to be in the range from 200 degrees C. to 400 degrees C.  
   
   
       4 . In an integrated circuit (IC) fabrication process, a method for forming a polycrystalline silicon (p-Si) film, the method comprising: 
 sputtering amorphous silicon (a-Si) material on a substrate;    supplying a gas mixture having a low hydrogen volume at the gas feed; and    forming an amorphous silicon film incorporating no more than 4% hydrogen, by atomic weight.    
   
   
       5 . The method of  claim 4  further comprising: 
 annealing the amorphous silicon film; and    forming a polycrystalline silicon film having a crystalline content in the range from 95% to 100% and a hydrogen content in the range from 1 percent by atomic weight (at %) to 3 at %.    
   
   
       6 . The method of  claim 4  wherein sputtering amorphous silicon material on a substrate includes setting the process temperature in the range from 200 degrees C. to 400 degrees C.  
   
   
       7 . In an integrated circuit (IC) fabrication process, a method for forming a polycrystalline silicon (p-Si) film, the method comprising: 
 sputtering amorphous silicon (a-Si) material on a substrate;    supplying a gas mixture including no more than 4%. hydrogen volume in the gas feed; forming an amorphous silicon film incorporating no more than 4% hydrogen, by atomic weight.    
   
   
       8 . The method of  claim 7  wherein supplying a gas mixture including no more than 4% hydrogen volume in the gas feed includes supplying a gas mixture substantially including Ar, mixed with no more than 4% hydrogen.  
   
   
       9 . The method of  claim 7  wherein supplying a gas mixture including no more than 4% hydrogen volume in the gas feed includes supplying a gas mixture including hydrogen in the range from 0.1% to 4%.  
   
   
       10 . The method of  claim 7  wherein forming an amorphous silicon film incorporating no more than 4% hydrogen, by atomic weight includes forming an amorphous silicon film having hydrogen content in the range from 0.1% to 4%, by atomic weight.  
   
   
       11 . The method of  claim 10  wherein forming an amorphous silicon film incorporating no more than 4% hydrogen, by atomic weight includes forming an amorphous silicon film having hydrogen content in the range from 1% to 4%, by atomic weight.  
   
   
       12 . The method of  claim 11  wherein forming an amorphous silicon film incorporating no more than 4% hydrogen, by atomic weight includes forming an amorphous silicon film having hydrogen content in the range from 3% to 4%, by atomic weight.  
   
   
       13 . The method of  claim 7  further comprising: 
 annealing the amorphous silicon film; and    forming a polycrystalline silicon film.    
   
   
       14 . The method of  claim 13  wherein annealing the amorphous silicon film includes annealing with a process selected from the group including rapid thermal annealing (RTA) and Excimer laser annealing (ELA).  
   
   
       15 . The method of  claim 13  wherein annealing the amorphous silicon film includes rapid thermal annealing at a temperature greater than approximately 600 degrees C.  
   
   
       16 . The method of  claim 13  wherein annealing the amorphous silicon film includes rapid thermal annealing at a temperature in the range from 600 degrees C. to 900 degrees C.  
   
   
       17 . The method of  claim 13  wherein forming an amorphous silicon film incorporating no more than 4% hydrogen, by atomic weight includes forming an amorphous silicon film incorporating hydrogen content in the range from 3% to 4%, by atomic weight; and 
 wherein annealing the amorphous silicon film includes rapid thermal annealing at a temperature in the range from 600 degrees C. to 900 degrees C.    
   
   
       18 . The method of  claim 7  wherein sputtering amorphous silicon amorphous silicon material on a substrate includes setting the process temperature to be in the range from 200 degrees C. to 400 degrees C.  
   
   
       19 . In the fabrication of a thin film transistor (TFT), a polysilicon (p-Si) film comprising: 
 a pre-anneal amorphous silicon (a-Si) film having a content of no more than 4% hydrogen, by atomic weight; and    a post-anneal polycrystalline silicon film having a crystalline content in the range from 95% to 100%, and a hydrogen content in the range from 1 percent by atomic weight (at %) to 3 at %.    
   
   
       20 . The silicon film of  claim 19  wherein the pre-anneal amorphous silicon film has a hydrogen content in the range from 0.1 at % to 4 at %.  
   
   
       21 . The silicon film of  claim 20  wherein the pre-anneal amorphous silicon film-has a hydrogen content in the range from 1 at % to 4 at %.  
   
   
       22 . The silicon film of  claim 21  wherein the pre-anneal amorphous silicon film has a hydrogen content in the range from 3 at % to 4 at %.  
   
   
       23 . In the fabrication of a thin film transistor (TFT), a pre-anneal film comprising: 
 amorphous silicon (a-Si); and    no more than 4% hydrogen content in the amorphous silicon, by atomic weight.    
   
   
       24 . The pre-anneal film of  claim 23  wherein the hydrogen content is in the range from 0.1 percent by atomic weight (at %) to 4 at %.  
   
   
       25 . The pre-anneal film of  claim 24  wherein the hydrogen content is in the range from 1 at % to 4 at %.  
   
   
       26 . The pre-anneal film of  claim 25  wherein the hydrogen content is in the range from 3 at % to 4 at %.  
   
   
       27 . In the fabrication of a liquid crystal display (LCD) including a thin film transistor (TFT), a polysilicon (p-Si) film comprising: 
 a pre-anneal amorphous silicon (a-Si) film having a content of no more than 4 percent by atomic weight (at %) hydrogen; and    a post-anneal polycrystalline silicon film having a crystalline content in the range from 95% to 100% and a hydrogen content in the range from 1 percent by atomic weight (at %) to 3 at %.