Semiconductor device with cobalt silicide contacts

Abstract

A semiconductor device that includes cobalt-silicide based contacts is disclosed, as well as a process for making the same. Combinations of alloyed layers of Co—Ti—along with layers of Co—are arranged and heat treated so as to effectuate a silicide reaction on a silicon substrate. The resulting structures have extremely low resistance, and show little line width dependence, thus making them particularly attractive for use in semiconductor devices and processes.

1 - 6 . (canceled)  
   
   
       7 . A method of forming a semiconductor device on a silicon based substrate comprising the steps of: 
 (a) forming a transistor on the silicon based substrate which includes at least one active region; and    (b) depositing a first metal layer on at least selected portions of the silicon based substrate within a first processing chamber of a semiconductor process cluster tool, including on said at least one active region, said first metal layer including an alloy of Cobalt and a refractory metal; and 
 wherein said alloy includes a percentage of refractory metal in the range of 1 to approximately 10 percent;  
   (c) performing a first heat treatment within the semiconductor process cluster tool and without exposing the silicon based substrate to an ambient after step (a) so as to convert at least part of said first metal layer and the silicon based substrate at said at least one active region into a first silicide composition having one or more cobalt silicide phases, said one or more cobalt silicide phases being characterized by a first resistitivity;    (d) performing a purge treatment within the first processing chamber of the semiconductor process cluster tool using a noble gas so as to remove contaminants and reactive gasses at least prior to depositing said first metal layer;    (e) performing a second heat treatment within the semiconductor process cluster tool so as to convert said first composition, including said one or more cobalt silicide phases, into a second silicide composition containing primarily a lower resistivity cobalt silicide phase, said lower resistivity cobalt silicide phase having a resistivity substantially less than said first resistivity; 
 wherein a low resistivity cobalt silicide contact is formed in said at least one active region.  
   
   
   
       8 . The method of  claim 7 , wherein said first heat treatment is performed as an in-situ anneal while said first metal layer is being deposited.  
   
   
       9 . The method of  claim 7 , wherein said refractory metal is titanium.  
   
   
       10 . The method of  claim 9 , wherein trace amounts of titanium remain near said second silicide composition.  
   
   
       11 . A method of forming semiconductor devices with silicide contacts on a semiconductor wafer comprising the steps of: 
 (a) forming a plurality of active devices in a semiconductor wafer, said plurality of active devices including a plurality of contact regions;    (b) introducing said semiconductor wafer into a first processing chamber of a semiconductor wafer processing apparatus;    (c) purging the first processing chamber with a gas derived from a noble element, and so as to provide an ambient that is substantially free of nitrogen;    (d) sputtering an alloy layer containing an alloy of Cobalt (Co) and a second refractory metal onto the silicon based substrate within the first processing chamber of the semiconductor wafer processing apparatus after step (c); 
 wherein said Co is present in said alloy layer in an amount sufficient for forming a plurality of low resistivity cobalt silicide contacts with said plurality of contact regions;  
   (e) heating the semiconductor wafer in-situ and during said sputtering step (a) within said first processing chamber of the semiconductor wafer processing cluster tool, at a temperature and time sufficient to cause at least partial silicidation of said plurality of contact regions and said alloy layer;    wherein said silicidation is achieved using only a single cobalt alloy layer.    
   
   
       12 . The method of  claim 11  wherein said target alloy includes a percentage of refractory metal in the range of 1 to approximately 10 percent.  
   
   
       13 . The method of  claim 11  further including a subsequent heating step at a higher temperature than that used in step (b) for completing said silicidation and for completing formation of said plurality of low resistivity cobalt silicide contacts.  
   
   
       14 . The method of  claim 11  wherein said heating step (b) is performed using a heating lamp so that a high temperature sputtering operation is performed on the semiconductor wafer.  
   
   
       15 - 32 . (canceled)  
   
   
       33 . The method of  claim 7 , wherein said noble gas used during said purge treatment is argon.  
   
   
       34 . The method of  claim 7 , wherein said alloy includes Cobalt and Titanium.  
   
   
       35 . The method of  claim 33 , wherein said alloy is sputtered in an argon based plasma maintained in said first processing chamber.  
   
   
       36 . The method of  claim 33 , wherein said Titanium operates, during formation of said first silicide composition and said second silicide composition, to reduce contamination of said cobalt and reactions by said alloy with other materials on said silicon based substrate.