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 - 20 . (canceled) 
     
     
         21 . A method for 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;   forming at least one diffusion barrier having cavities in the substrate, wherein the diffusion barrier abuts ends of the first and second diffusion regions, the diffusion barrier reduces out-diffusion of dopants from the first and second diffusion regions.   
     
     
         22 . The method of  claim 21  wherein the diffusion barrier abuts bottom ends of the first and second diffusion regions. 
     
     
         23 . The method of  claim 22  comprising:
 forming a plurality of shallow trench isolation (STI) regions in the substrate. 
 
     
     
         24 . The method of  claim 23  wherein the diffusion barrier spans a substantial distance from one STI region to another adjacent STI region. 
     
     
         25 . The method of  claim 24  wherein forming the diffusion barrier comprises:
 implanting an implant medium in the substrate to form an implant region of which the diffusion barrier is to be formed; and 
 annealing the implant region to form the cavities. 
 
     
     
         26 . The method of  claim 25  wherein the implant medium comprises He, hydrogen, argon atoms or a combination thereof. 
     
     
         27 . The method of  claim 24  wherein forming the first and second diffusion regions comprises:
 forming spacers adjacent to sidewalls of the gate structure; and 
 implanting the dopants to form the first and second diffusion regions. 
 
     
     
         28 . The method of  claim 21  wherein the diffusion barrier comprises:
 first and second diffusion barriers, wherein the first diffusion barrier abuts a bottom of the first diffusion region and the second diffusion barrier abuts a bottom of the second diffusion barriers. 
 
     
     
         29 . The method of  claim 28  wherein forming diffusion barrier is performed after forming the gate structure. 
     
     
         30 . The method of  claim 28  comprising:
 providing a capping layer over the gate structure; and 
 forming spacers adjacent to sidewalls of the gate structure. 
 
     
     
         31 . The method of  claim 30  wherein forming the diffusion barrier comprises:
 implanting an implant medium in the substrate to form an implant region of which the diffusion barrier is to be formed, wherein the spacers and the capping layer mask a channel region below the gate structure from the implant medium; and 
 annealing the implant region to form the cavities. 
 
     
     
         32 . The method of  claim 31  wherein the implant medium comprises He, hydrogen, argon atoms or a combination thereof. 
     
     
         33 . A method for 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;   forming a diffusion barrier having cavities in the substrate, wherein the diffusion barrier is disposed in between the first and second diffusion regions, the diffusion barrier reduces out-diffusion of dopants from the first and second diffusion regions.   
     
     
         34 . The method of  claim 33  wherein the diffusion barrier is formed immediately below a channel region which is disposed below the gate structure. 
     
     
         35 . The method of  claim 34  wherein the diffusion barrier is formed at a depth corresponding to lower portions of the first and second diffusion regions. 
     
     
         36 . The method of  claim 34  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. 
 
     
     
         37 . The method of  claim 36  wherein the implant medium comprises He, hydrogen, argon atoms or a combination thereof. 
     
     
         38 . A device comprising:
 a substrate;   a gate structure disposed on the substrate;   first and second diffusion regions disposed in the substrate on opposed sides of the gate structure;   at least one diffusion barrier having cavities disposed in the substrate, wherein the at least one diffusion barrier abuts ends of the first and second diffusion regions, the diffusion barrier reduces out-diffusion of dopants from the first and second diffusion regions.   
     
     
         39 . The device of  claim 38  comprising:
 a plurality of shallow trench isolation (STI) regions in the substrate, wherein the diffusion barrier spans a substantial distance from one STI region to another adjacent STI region. 
 
     
     
         40 . The device of  claim 39  wherein the diffusion barrier abuts bottom ends of the first and second diffusion regions.