Using Oxynitride Spacer to Reduce Parasitic Capacitance in CMOS Devices

Abstract

A complementary metal oxide semiconductor (CMOS) device has a substrate 100 , a gate structure 108 disposed atop the substrate, and spacers 250 , deposited on opposite sides of the gate structure 108 to govern formation of deep source drain regions S, D in the substrate. Spacers 250 are formed of an oxynitride (SiO x N y C z ) wherein x and y are non-zero but z may be zero or greater; such oxynitride spacers reduce parasitic capacitance, thus improving device performance. A method of fabricating a portion of a complementary metal oxide semiconductor (CMOS) device involves providing a substrate 100 , forming a gate structure 108 over the substrate, depositing a first layer 104 atop the substrate on opposite sides of the gate structure to govern formation of deep source drain regions in the substrate, depositing an oxynitride (SiO x N y C z ) layer 250 atop the first layer (in which x and y are non-zero but z may be zero or greater), depositing a second layer 112 atop the oxynitride layer, and depositing a nitride layer 114 B atop the second layer.

1 - 13 . (canceled)  
   
   
       14 . A method of fabricating a portion of a complementary metal oxide semiconductor (CMOS) device, the method comprising: 
 providing a substrate;    forming a gate structure over the substrate;    depositing a first layer atop the substrate on opposite sides of the gate structure to govern formation of deep source drain regions in the substrate;    depositing an oxynitride (SiO x N y C z ) layer atop the first layer, wherein x and y are non-zero but z may be zero or greater;    depositing a second layer atop the oxynitride layer; and    depositing a nitride layer atop the second layer.    
   
   
       15 . The method of  claim 14 , wherein: 
 the oxynitride depositing step is a low pressure chemical vapor deposition (LPCVD) process.    
   
   
       16 . The method of  claim 15 , wherein: 
 the LPCVD process involves gas mixtures including ammonia and nitrous oxide.    
   
   
       17 . The method of  claim 14 , wherein the oxynitride layer depositing step includes: 
 depositing a carbon doped oxynitride (SiO x N y C z ) layer, wherein z>0, using an organic precursors such as bis t-ButylaminoSilane (BTBAS, C 8 H 22 N 2 Si).    
   
   
       18 . The method of  claim 14 , wherein the oxynitride layer depositing step includes: 
 forming the oxynitride (SiO x N y C z ) layer with a nitrogen/oxygen ratio that varies as a function of depth, with less oxygen content near faces of the oxynitride layer than at a center of the oxynitride layer so that a nitrogen/oxygen ratio is greatest near the faces of the oxynitride layer.