Low-resistive tungsten silicide layer strongly adhered to lower layer and semiconductor device using the same

Abstract

Tungsten silicide WSi x is grown through reduction of WF 6 with SiCl 2 H 2 , and the flow rate between WF 6 and SiCl 2 H 2 is controlled in such a manner that the composition ratio x ranges from 2.0 to 2.2 in an initial stage for forming cores on a doped polysilicon layer, and is treated with heat at 700 degrees to 850 degrees in centigrade so as to grow tungsten silicide grains with <001>orientation faster than tungsten silicide grains with <101>orientation; the tungsten silicide WSi x is tightly adhered to the doped polysilicon, and the abnormal oxidation is restricted during the heat treatment.

What is claimed is:  
     
         1 . A tungsten silicide layer incorporated in a semiconductor device, including tungsten silicide grains different in orientation having at least first tungsten silicide grains with <101>orientation and secondtungsten silicide grains with <001>orientation having a volume ratio largest of all.  
     
     
         2 . The tungsten silicide layer as set forth in    claim 1   , said second tungsten silicide grains are equal to or greater than 50 percent in volume.  
     
     
         3 . The tungsten silicide layer as set forth in    claim 1   , in which said first tungsten silicide grains have a volume ratio smallest of all.  
     
     
         4 . The tungsten silicide layer as set forth in    claim 3   , in which said ratio of said first tungsten silicide grains is equal to or less than 10 percent.  
     
     
         5 . The tungsten silicide layer as set forth in    claim 1   , in which the tungsten silicide has a first intensity peak at (101) indicative of said first tungsten silicide grains and a second intensity peak at (002) indicative of said second tungsten silicide grains in an x-ray diffraction analysis, and said first intensity peak is equal to or less than 10 percent of said second intensity peak.  
     
     
         6 . A semiconductor device fabricated on a substrate, comprising at least one composite conductive path including a lower layer formed of silicon and an upper layer formed of tungsten silicide including tungsten silicide grains different in orientation and having at least first tungsten silicide grains with <101>orientation and second tungsten silicide grains with <001>orientation having a volume ratio largest of all.  
     
     
         7 . The semiconductor device as set forth in    claim 6   , in which said at least one composite conductive path serves as a gate electrode of a field effect transistor.  
     
     
         8 . The semiconductor device as set forth in    claim 1   , in which said at least one composite conductive path serves as a signal propagation path.  
     
     
         9 . The semiconductor device as set forth in    claim 8   , further comprising another composite conductive path serving as a gate electrode of a field effect transistor.  
     
     
         10 . The tungsten semiconductor device as set forth in    claim 6   , in which said second tungsten silicide grains are equal to or greater than 50 percent in volume.  
     
     
         11 . The semiconductor device as set forth in    claim 6   , in which said first tungsten silicide grains have a volume ratio smallest of all.  
     
     
         12 . The semiconductor device as set forth in    claim 11   , in which said ratio of said first tungsten silicide grains is equal to or less than 10 percent.  
     
     
         13 . The semiconductor device as set forth in    claim 6   , in which the tungsten silicide has a first intensity peak at (101) indicative of said first tungsten silicide grains and a second intensity peak at (002) indicative of said second tungsten silicide grains in an x-ray diffraction analysis, and said first intensity peak is equal to or less than 10 percent of said second intensity peak.  
     
     
         14 . A process for fabricating a semiconductor device, comprising the steps of: 
 a) preparing a substrate structure having at least a silicon layer;    b) depositing a tungsten silicide on said silicon layer for producing a tungsten silicide layer, at least a part of said tungsten silicide layer at the boundary to said silicon layer being expressed as WSi x  where the composition ratio x ranges from 2.0 to 2.2; and    c) treating said tungsten silicide layer with heat at 700 degrees to 850 degrees in centigrade so as to render said tungsten silicide layer including plural tungsten silicide grains different in orientation and having at least first tungsten silicide grains with <101>orientation and second tungsten silicide grains with <001>orientation having a volume ratio largest of all.    
     
     
         15 . The process as set forth in    claim 14   , further comprising the step of d) exposing said tungsten silicide layer to an oxidizing atmosphere.  
     
     
         16 . The process as set forth in    claim 14   , in which said silicon layer is polycrystalline.