Method and apparatus for improving film deposition uniformity on a substrate

Abstract

A method and apparatus for depositing a film on a substrate. According to the present invention a prewafer reaction layer is deposited onto a susceptor placed in the reaction chamber to form a prewafer reaction layer coated susceptor prior to film deposition. A deposition gas is then fed into the reaction chamber so that it flows over the prewafer reaction layer coated susceptor and the substrate to form a film on the prewafer reaction layer coated susceptor and the substrate.

We claim:  
     
         1 . A method of forming a film on a substrate, said method comprising the steps of: 
 forming a prewafer reaction layer adjacent to a substrate; and    flowing a deposition gas over said prewafer reaction layer and over said substrate to deposit said film on said prewafer reaction layer and said substrate.    
     
     
         2 . The method of  claim 1  wherein said prewafer reaction layer is silicon.  
     
     
         3 . The method of  claim 2  wherein said silicon layer is amorphous silicon.  
     
     
         4 . The method of  claim 2  wherein said silicon layer is polycrystalline silicon.  
     
     
         5 . The method of  claim 1  wherein said prewafer reaction layer is titanium silicide.  
     
     
         6 . The method of  claim 1  wherein said film is titanium silicide.  
     
     
         7 . A method of depositing a film on a substrate, said method comprising the steps of: 
 depositing a prewafer reaction layer onto a susceptor to form a prereaction layer coated susceptor;    placing a substrate onto said prewafer reaction layer coated susceptor; and    flowing a deposition gas over said prewafer reaction layer coated susceptor and over said substrate so that said deposition gas reacts with said prewafer reaction layer coated susceptor and with said substrate to form a film on said substrate and said susceptor.    
     
     
         8 . The method of  claim 7  wherein said prewafer reaction layer comprises silicon.  
     
     
         9 . The method of  claim 7  wherein said prewafer reaction layer is polycrystalline silicon.  
     
     
         10 . The method of  claim 7  wherein said prewafer reaction layer is amorphous silicon.  
     
     
         11 . The method of  claim 7  wherein said prewafer reaction layer is titanium silicide.  
     
     
         12 . The method of  claim 7  wherein said prewafer reaction layer and said film are the same material.  
     
     
         13 . A method of s electively depositing a titanium silicide layer on a wafer, said method comprising the steps of: 
 a) depositing a silicon layer onto a susceptor and a preheat ring to form a silicon coated susceptor and a silicon coated preheat ring;    b) placing a wafer having a silicon containing surface and an insulating surface on said silicon coated susceptor; and    c) flowing a titanium containing deposition gas over said silicon coated preheat ring, said silicon coated susceptor and said wafer and reacting said titanium containing deposition gas with said silicon coated preheat ring said silicon coated susceptor and said silicon coated surface of said wafer to selectively form titanium-silicide on said wafer, said preheat ring, and said susceptor.    
     
     
         14 . The method of  claim 13  further comprising the step of: 
 prior to depositing said silicon layer cleaning said susceptor.  
 
     
     
         15 . The method of  claim 13  further comprising the steps of: 
 repeating steps b) and c) a plurality of times; and  
 after repeating steps b) and c) a plurality of times, removing said titanium-silicide from said susceptor and said preheat ring.  
 
     
     
         16 . The method of  claim 13  wherein said silicon layer is polycrystalline silicon.  
     
     
         17 . The method of  claim 13  wherein said deposition gas is titanium tetrachloride (TiCl 4 ).  
     
     
         18 . A method of forming a silicon/silicide film on a substrate comprising the steps of: 
 placing a substrate on a susceptor in a chamber;    depositing a silicon film over said susceptor and over said substrate to form a silicon coated susceptor and substrate;    flowing a silicide deposition gas into said chamber in such a manner that said silicide deposition gas flows over said silicon coated susceptor prior to reaching said silicon coated substrate; and    forming a silicide on said silicon coated susceptor and on said silicon coated substrate.    
     
     
         19 . The method of  claim 18  further comprising the step of: 
 placing a second wafer on said susceptor;  
 depositing a second silicon film over said silicide layer on said susceptor and over said second wafer; and  
 depositing a second silicide film on said second silicon film.  
 
     
     
         20 . The method of  claim 18  wherein said silicide film is titanium silicide.  
     
     
         21 . An apparatus for depositing a film on a substrate, said apparatus comprising: 
 a substrate holder located in a reaction chamber, said substrate holder having a substrate placement location; and    a prewafer reaction layer adjacent to said substrate placement location and positioned between a deposition gas inlet and said substrate placement location.    
     
     
         22 . The apparatus of  claim 21  wherein said prewafer reaction layer is formed on a preheat ring which surrounds said substrate holder and formed on said substrate holder.  
     
     
         23 . The apparatus of  claim 21  wherein said prewafer reaction layer has a size and thickness sufficient to reduce wafer edge effects and cause uniform deposition to occur at a substantially uniform rate across a substrate placed on said substrate placement location.