Silicon germanium film formation method and structure

Abstract

Epitaxial deposition of silicon germanium in a semiconductor device is achieved without using masks. Nucleation delays induced by interactions with dopants present before deposition of the silicon germanium are used to determine a period over which an exposed substrate surface may be subjected to epitaxial deposition to form a layer of SiGe on desired parts with substantially no deposition on other parts. Dopant concentration may be changed to achieve desired thicknesses within preferred deposition times. Resulting deposited SiGe is substantially devoid of growth edge effects.

1 . A semiconductor device structure comprising:
 a first FET having a plug formed from an epitaxially deposited first material in a channel of the first FET;   a second FET having a channel formed from the epitaxially deposited first material; and   wherein, during a predetermined period, the first material is deposited epitaxially substantially devoid of growth edge effects.   
     
     
         2 . The structure of  claim 1 , wherein the epitaxially deposited first material includes silicon germanium (SiGe), the first FET is a PFET, the second FET is an NFET, the structure further comprises a trench isolation between the NFET and the PFET, and the epitaxially deposited SiGe is substantially free of epitaxial growth edge effects. 
     
     
         3 . The structure of  claim 2 , wherein the substrate includes silicon and the PFET includes a first region doped with a N-type dopant such that the SiGe accumulates on the first region during the predetermined period. 
     
     
         4 . The structure of  claim 1 , wherein one of the first and second FETs includes a first dopant in a first concentration and the predetermined period of epitaxial deposition of the first material is dependent on the first concentration. 
     
     
         5 . A semiconductor structure comprising:
 a substrate with a first region and a second region, the first region being doped with a first dopant; and   a layer of silicon germanium (SiGe) on substantially only one of the first region or the second region and substantially free of edge effects, the layer being formed by exposing the first and second regions to a deposition stream of SiGe for at least a predetermined period without coating the second region prior to deposition.   
     
     
         6 . The semiconductor structure of  claim 5 , wherein the first dopant is an N-type dopant and the SiGe layer is on substantially only the second region. 
     
     
         7 . The semiconductor structure of  claim 6 , wherein the first dopant includes arsenic. 
     
     
         8 . The semiconductor structure of  claim 6 , wherein the second region is doped with a P-type dopant. 
     
     
         9 . The semiconductor structure of  claim 8 , wherein the P-type dopant includes boron. 
     
     
         10 . The semiconductor structure of  claim 5 , wherein the first dopant is a P-type dopant and the SiGe layer is on substantially only the first region. 
     
     
         11 . The semiconductor structure of  claim 10 , wherein the first dopant includes boron. 
     
     
         12 . The semiconductor structure of  claim 10 , wherein the second region is doped with an N-type dopant. 
     
     
         13 . The semiconductor structure of  claim 12 , wherein the N-type dopant includes arsenic. 
     
     
         14 . A semiconductor structure formed according to a process including:
 providing a substrate;   defining a first region of the substrate and a second region of the substrate;   doping the first region of the substrate with a first dopant in a first concentration; and   exposing a surface of the substrate of the first and second regions to a deposition stream of silicon germanium (SiGe) for at least a predetermined period dependent on at least the first concentration so that:
 responsive to the first dopant being a P-type dopant, a layer of SiGe forms on the first region during the predetermined period with substantially no deposition of SiGe on the second region; and 
 responsive to the first dopant being an N-type dopant, a layer of SiGe forms on the second region with substantially no deposition on the first region. 
   
     
     
         15 . The semiconductor structure of  claim 14 , wherein the process further comprises doping the second region with a second dopant in a second concentration so that:
 responsive to the second dopant being a P-type dopant, a layer of SiGe forms on the second region during the predetermined period; and   responsive to the second dopant being an N-type dopant, substantially no SiGe deposition occurs on the first region.   
     
     
         16 . The semiconductor structure of  claim 15 , wherein the first dopant is a P-type dopant and the second dopant is an N-type dopant. 
     
     
         17 . The semiconductor structure of  claim 14 , wherein the second region is substantially dopant free during deposition of the SiGe.