Semiconductor device and manufacturing method thereof

Abstract

A method includes forming a gate structure on a substrate; forming a gate spacer on a sidewall of the gate structure; forming a carbon-containing layer on the gate spacer; diffusing carbon from the carbon-containing layer into a portion of the substrate below the gate spacer; forming a recess in the substrate on one side of the gate spacer opposite to the gate structure; and forming an epitaxy feature in the recess of the substrate.

What is claimed is: 
     
         1 . A method, comprising:
 forming a gate structure on a substrate;   forming a gate spacer layer on a sidewall of the gate structure;   forming a carbon-containing layer on the gate spacer layer;   diffusing carbon from the carbon-containing layer into a portion of the substrate below the gate spacer layer;   forming a recess in the substrate on one side of the gate spacer layer opposite to the gate structure; and   forming an epitaxy feature in the recess of the substrate.   
     
     
         2 . The method of  claim 1 , wherein the carbon-containing layer is formed using a plasma-assisted process. 
     
     
         3 . The method of  claim 1 , further comprising:
 removing the carbon-containing layer.   
     
     
         4 . The method of  claim 1 , wherein the forming the recess is performed prior to the forming the carbon-containing layer, and wherein the carbon-containing layer is further formed in the recess. 
     
     
         5 . The method of  claim 4 , wherein the epitaxy feature is formed over the carbon-containing layer in the recess. 
     
     
         6 . The method of  claim 1 , further comprising etching the gate spacer layer to expose a top surface of the substrate prior to forming the recess in the substrate. 
     
     
         7 . The method of  claim 1 , wherein diffusing carbon from the carbon-containing layer into the portion of the substrate comprises performing an annealing process. 
     
     
         8 . A method, comprising:
 forming a gate structure on a substrate;   forming a gate spacer layer on a sidewall of the gate structure;   forming a carbon-containing layer over the gate spacer layer;   removing the carbon-containing layer;   removing a horizontal portion of the gate spacer layer to expose a surface of the substrate; and   forming an epitaxy structure in the substrate.   
     
     
         9 . The method of  claim 8 , further comprising performing an annealing process after forming the carbon-containing layer and prior to removing the carbon-containing layer. 
     
     
         10 . The method of  claim 9 , wherein the annealing process is performed such that first carbon-containing diffusion barriers are formed in the gate spacer layer and second carbon-containing diffusion barriers are formed in the substrate, and the first carbon-containing diffusion barriers are vertically aligned with the second carbon-containing diffusion barriers. 
     
     
         11 . The method of  claim 10 , wherein one of the second carbon-containing diffusion barriers is below an angular corner formed by an up-slant facet and a down-slant facet of the epitaxy structure. 
     
     
         12 . The method of  claim 9 , wherein the carbon-containing layer is formed using a plasma-assisted process. 
     
     
         13 . The method of  claim 9 , wherein the carbon-containing layer is above a top surface of the gate structure. 
     
     
         14 . The method of  claim 8 , wherein the carbon-containing layer is formed using a plasma-assisted process. 
     
     
         15 . A method, comprising:
 forming a gate structure over a channel region of a substrate;   forming a gate spacer layer on a sidewall of the gate structure;   forming a first carbon-containing diffusion barrier in the gate spacer layer and forming a second carbon-containing diffusion barrier in the substrate, wherein the first carbon-containing diffusion barrier in the gate spacer layer is vertically aligned with the second carbon-containing diffusion barrier; and   forming an epitaxy feature on the substrate.   
     
     
         16 . The method of  claim 15 , wherein forming the first carbon-containing diffusion barrier and the second carbon-containing diffusion barrier comprises:
 forming a carbon-containing layer over the gate spacer layer; and   diffusing carbon from the carbon-containing layer into the gate spacer layer and into the substrate.   
     
     
         17 . The method of  claim 16 , further comprising removing the carbon-containing layer after diffusing carbon from the carbon-containing layer into the gate spacer layer and into the substrate. 
     
     
         18 . The method of  claim 16 , wherein diffusing carbon from the carbon-containing layer into the gate spacer layer and into the substrate comprises performing an annealing process. 
     
     
         19 . The method of  claim 16 , wherein the carbon-containing layer is above a top surface of the gate structure. 
     
     
         20 . The method of  claim 15 , further comprising removing a horizontal portion of the gate spacer layer to form a gate spacer prior to forming the epitaxy feature.