Diffusion barrier and method of formation thereof

Abstract

A method of forming a device is presented. The method includes providing a structure having first and second regions. A diffusion barrier is formed between at least a portion of the first and second regions. The diffusion barrier comprises cavities that reduce diffusion of elements between the first and second regions.

What is claimed is: 
     
         1 . A method of forming a device comprising:
 providing a substrate;   forming a gate structure over the substrate;   forming first and second diffusion regions in the substrate on opposed sides of the gate structure; and   forming a diffusion barrier having cavities in the substrate in between the first and second diffusion regions, wherein the diffusion barrier is formed immediately below a channel region which is disposed below the gate structure.   
     
     
         2 . The method of  claim 1  wherein the diffusion barrier is formed at a depth corresponding to lower portions of the first and second diffusion regions. 
     
     
         3 . The method of  claim 1  wherein forming the diffusion barrier comprises:
 providing a mask on top of the substrate, the mask comprises a cavity that exposes a portion of a top surface of the substrate of which the gate structure is to be formed; 
 implanting an implant medium in the portion exposed by the cavity to form an implant region below a portion of the substrate which forms the channel region; and 
 annealing the implant region to form the cavities. 
 
     
     
         4 . The method of  claim 3  wherein the mask comprises a silicon oxide layer and a silicon nitride layer over the silicon oxide layer. 
     
     
         5 . The method of  claim 3  wherein the mask comprises a polymer-based photoresist material. 
     
     
         6 . The method of  claim 3  wherein the implant medium comprises He, hydrogen, argon atoms or a combination thereof. 
     
     
         7 . The method of  claim 3  wherein implanting the implant medium is performed at an energy in the range of from around 2 keV to around 100 keV and at a dose of around 1×10 13  to around 5×10 15  cm −2 . 
     
     
         8 . The method of  claim 3  wherein forming the gate structure comprises:
 forming a gate dielectric layer over the exposed portion of the top surface of the substrate; 
 blanket depositing a gate electrode layer over the mask; and 
 performing an etch back process to form a gate electrode over the gate dielectric layer in the cavity. 
 
     
     
         9 . The method of  claim 8  comprises:
 removing the mask; and 
 forming spacer elements on sidewalls of the gate structure, wherein the first and second diffusion regions are source and drain regions which are formed after forming the spacer elements and the diffusion barrier. 
 
     
     
         10 . A method of forming a device comprising:
 providing a substrate;   forming a gate structure over the substrate;   forming first and second diffusion regions in the substrate on opposed sides of the gate structure; and   forming at least a first diffusion barrier having cavities in the substrate in between the first and second diffusion regions, wherein the first diffusion barrier is formed immediately below a channel region which is disposed below the gate structure.   
     
     
         11 . The method of  claim 10  wherein the first diffusion barrier is formed at a depth corresponding to lower portions of the first and second diffusion regions. 
     
     
         12 . The method of  claim 10  wherein the at least a first diffusion barrier reduces out-diffusion of dopants from the first and second diffusion regions. 
     
     
         13 . The method of  claim 10  wherein forming the at least a first diffusion barrier comprises forming second and third diffusion barriers, wherein the second and third diffusion barriers are separated from each other and are formed immediately adjacent to bottom ends of the first and second diffusion regions. 
     
     
         14 . The method of  claim 10  comprising:
 forming a plurality of shallow trench isolation (STI) regions in the substrate; and wherein 
 forming the at least a first diffusion barrier comprises forming a second diffusion barrier, wherein the second diffusion barrier is formed immediately adjacent to bottom ends of the first and second diffusion regions and the second diffusion barrier spans a substantial distance from one STI region to another adjacent STI region. 
 
     
     
         15 . A device comprising:
 a substrate;   a gate structure over the substrate;   first and second diffusion regions disposed in the substrate on opposed sides of the gate structure; and   at least a first diffusion barrier having cavities disposed in the substrate in between the first and second diffusion regions, wherein the first diffusion barrier is disposed immediately below a channel region which is disposed below the gate structure.   
     
     
         16 . The device of  claim 15  wherein the first diffusion barrier is formed at a depth corresponding to lower portions of the first and second diffusion regions. 
     
     
         17 . The device of  claim 15  wherein the first and second diffusion regions are source and drain regions. 
     
     
         18 . The device of  claim 15  wherein the at least a first diffusion barrier comprises a second diffusion barrier, wherein the second diffusion barrier is disposed immediately adjacent to a bottom end of the first or second diffusion region. 
     
     
         19 . The device of  claim 15  wherein the at least a first diffusion barrier comprises second and third diffusion barriers, wherein the second and third diffusion barriers are separated from each other and are disposed immediately adjacent to bottom ends of the first and second diffusion regions. 
     
     
         20 . The device of  claim 15  comprising:
 a plurality of shallow trench isolation (STI) regions in the substrate; and wherein 
 the at least a first diffusion barrier comprises a second diffusion barrier, wherein the second diffusion barrier is disposed immediately adjacent to bottom ends of the first and second diffusion regions and the second diffusion barrier spans a substantial distance from one STI region to another adjacent STI region.