Method of forming a semiconductor device with a multi-layer WSix film with small grain size structure, and a semiconductor device having a polysilicon layer with a multi-layer WSix film formed thereon

Abstract

A method of forming a semiconductor device with a polysilicon layer having a multi-layer tungsten-silicide (WSi x ) film formed on a surface thereof includes the steps of (1) forming a first layer of tungsten-silicide on the surface of the polysilicon layer; (2) forming a second layer of a material selected from tungsten and silicon on the first layer; (3) forming a third layer of tungsten-silicide on the second layer; and (4) thermally treating the multi-layer film resulting from steps (a)-(c) to form a multi-layer WSi x film on the surface of the polysilicon layer, the multi-layer WSi x film having a uniform small grain size. In various embodiments, steps (1)-(3) may be repeated one or more times. A semiconductor device includes a semiconductor body having a polysilicon layer formed on a surface thereof and a multilayered WSi x film formed on a surface of the polysilicon layer by the process described above.

What is claimed is:  
     
         1 . A method of forming a semiconductor device having a multi-layer tungsten-silicide (WSi x ) film formed on a surface thereof, said method comprising the steps of: 
 (a) providing a semiconductor substrate having a surface;    (b) forming a first layer of tungsten-silicide on the surface;    (c) forming a second layer of a material selected from tungsten and silicon on said first layer;    (d) forming a third layer of tungsten-silicide on said second layer; and    (e) thermally treating the multi-layer film resulting from steps (a)-(d) to form a WSi x  film having a plurality of layers, each layer of said plurality of layers having a uniform grain size.    
     
     
         2 . A method according to  claim 1 , comprising repeating steps (c)-(d) one or more times.  
     
     
         3 . A method according to  claim 1 , wherein steps (b) and (d) comprise chemical vapor deposition according to the chemical formula: 
 (1.5-5 sccm gas)WF 6 +(60-200 sccm gas)SiH 2 Cl 2 , at a temperature in the range of about 400-600 degrees C. and a pressure in the range of about 1-1.7 Torr.    
     
     
         4 . A method according to  claim 2 , wherein step (b) comprises one of: 
 (i) depositing said tungsten layer by chemical vapor deposition according to the formula (100-140 sccm gas)WF 6 +(60-200 sccm gas)H 2 , at a temperature in the range of about 400-600 degrees C. and at a pressure in the range of about 30-90 Torr; and    (ii) depositing said silicon layer by thermal decomposition of one of SiH and SiH 2 Cl 2  at a temperature in the range of about 400-600 degrees C.    
     
     
         5 . A method according to  claim 4 , wherein a total thickness of said first layer deposited by step (b) and all repetitions of steps (c)-(d) is in a range of about 400-1200 Å.  
     
     
         6 . A method according to  claim 5 , wherein step (e) comprises an annealing process at greater than about 1000 degrees C.  
     
     
         7 . A method according to  claim 4 , wherein step (c) comprises one of depositing tungsten in a thickness in the range of about 10 Å to 20 Å and depositing silicon in a thickness in the range of about 10 Å to 20 Å.  
     
     
         8 . A method according to  claim 1 , wherein a total thickness of said first, second and third layers is T, and said second layer is of thickness in a range of about T/5 to T/2.  
     
     
         9 . A method according to  claim 8 , wherein a total thickness of said first, second and third layers is in a range of about 400-1200 Å.  
     
     
         10 . A method according to  claim 8 , wherein step (d) comprises an annealing process at greater than 1000 degrees C.  
     
     
         11 . A method according to  claim 1 , wherein said semiconductor device is provided with a polysilicon layer with said multi-layer tungsten-silicide (WSi x ) film formed on a surface of said polysilicon layer.  
     
     
         12 . A method according to  claim 1 , wherein said first layer is disposed on said surface of said semiconductor device and said first layer is thinner and has a higher x-ratio than said third layer.  
     
     
         13 . A method according to  claim 2 , wherein said layer formed by step (b) is thinner and has a higher x-ratio than each said layer formed by step (d).  
     
     
         14 . A semiconductor device comprising a semiconductor body having a surface and a multilayered WSi x  film formed on said surface, said multilayered WSi x  film being formed on said surface by a process comprising the steps of: 
 (a) forming a first layer of tungsten-silicide on the surface of said surface;    (b) forming a second layer of a material selected from tungsten and silicon on said first layer;    (c) forming a third layer of tungsten-silicide on said second layer; and    (d) thermally treating the multi-layer film resulting from steps (a)-(c) to form WSi x  film having a plurality of layers, each layer of said plurality of layers having a uniform grain size.    
     
     
         15 . A semiconductor device according to  claim 14 , comprising repeating steps (b)-(c) one or more times.  
     
     
         16 . A semiconductor device according to  claim 14 , wherein steps (a) and (c) comprise chemical vapor deposition according to the chemical formula: 
 (1.5-5 sccm gas)WF 6 +(60-200 sccm gas)SiH 2 Cl 2 , at a temperature in the range of about 400-600 degrees C. and a pressure in the range of about 1-1.7 Torr.    
     
     
         17 . A semiconductor device according to  claim 15 , wherein step (b) comprises one of: 
 (i) depositing said tungsten layer by chemical vapor deposition according to the formula (100-140 sccm gas)WF 6  +(60-200 sccm gas)H 2 , at a temperature in the range of about 400-600 degrees C. and at a pressure in the range of about 30-90 Torr; and    (ii) depositing said silicon layer by thermal decomposition of one of SiH and SiH 2 Cl 2  at a temperature in the range of about 400-600 degrees C.    
     
     
         18 . A semiconductor device according to  claim 17 , wherein a total thickness of said first layer deposited by step (a) and layers provided by all repetitions of steps (b) (c) is in the range from 400-1200 Å.  
     
     
         19 . A semiconductor device according to  claim 18 , wherein step (d) comprises an annealing process at greater than 1000 degrees C.  
     
     
         20 . A semiconductor device according to  claim 17 , wherein step (b) comprises one of depositing tungsten in a thickness in the range of about 10 Å to 20 Å and depositing silicon in a thickness in the range of about 10 Å to 20 Å.  
     
     
         21 . A semiconductor device according to  claim 14 , wherein a total thickness of said first, second and third layers is T, and said second layer is of thickness in a range of about T/5 to T/2.  
     
     
         22 . A semiconductor device according to  claim 21 , wherein step (d) comprises an annealing process at greater than 1000 degrees C.  
     
     
         23 . A semiconductor device according to  claim 14 , wherein a total thickness of said first, second and third layers is in the range from 400-1200 Å.  
     
     
         24 . A semiconductor device according to  claim 14 , wherein said semiconductor device is provided with a polysilicon layer on a surface of said semiconductor device and said multi-layer tungsten-silicide (WSi x ) film is formed on a surface of said polysilicon layer.  
     
     
         25 . A semiconductor device according to  claim 14 , wherein said first layer is disposed on said surface of said semiconductor device and said first layer is thinner and has a higher x-ratio than said third layer.  
     
     
         26 . A semiconductor device according to  claim 15 , wherein said layer formed by step (a) is thinner and has a higher x-ratio than each said layer formed by step (c).