Deposition of silicon germanium on silicon-on-insulator structures and bulk substrates

Abstract

Methods are provided for producing SiGe-on-insulator structures and for forming strain-relaxed SiGe layers on silicon while minimizing defects. Amorphous SiGe layers are deposited by CVD from trisilane and GeH 4 . The amorphous SiGe layers are recrystallized over silicon by melt or solid phase epitaxy (SPE) processes. The melt processes preferably also cause diffusion of germanium to dilute the overall germanium content and essentially consume the silicon overlying the insulator. The SPE process can be conducted with or without diffusion of germanium into the underlying silicon, and so is applicable to SOI as well as conventional semiconductor substrates.

1 . A method of forming a strain-relaxed SiGe layer on a substrate that includes a silicon layer, the method comprising: 
 covering the silicon layer with less than about a monolayer of oxide;    depositing over the silicon layer an amorphous SiGe layer by chemical vapor deposition from trisilane; and    conducting solid phase epitaxy to crystallize the amorphous SiGe layer, thereby forming a strain-relaxed SiGe layer.    
     
     
         2 . The method of  claim 1 , wherein the oxide is a native oxide.  
     
     
         3 . The method of  claim 1 , wherein the oxide is a chemical oxide.  
     
     
         4 . The method of  claim 1 , wherein the less than about a monolayer of oxide is formed on the substrate by deposition of more than one monolayer of oxide, followed by etching.  
     
     
         5 . The method of  claim 1 , wherein the germanium concentration in the strain-relaxed SiGe layer is between about 20% and about 60%.  
     
     
         6 . A method of forming a strained silicon layer on a relaxed SiGe layer, the method comprising: 
 depositing a SiGe layer on a first Si layer by chemical vapor deposition from trisilane and a germanium precursor, thereby forming an interface between the first Si layer and the deposited SiGe layer;    converting the deposited SiGe layer to a strain-relaxed single crystal SiGe layer; and    heteroepitaxially depositing a second Si layer on the strain-relaxed single crystal SiGe layer to form a strained Si layer, wherein the strain-relaxed single crystal SiGe layer has fewer than 10 7  threading dislocations per square centimeter.    
     
     
         7 . The method of  claim 6 , wherein the deposited SiGe layer is amorphous.  
     
     
         8 . The method of  claim 6 , wherein the deposited SiGe layer is a strained heteroepitaxial layer.  
     
     
         9 . The method of  claim 8 , wherein the deposited SiGe layer is deposited to a thickness below its critical thickness at the temperature during deposition of the deposited SiGe layer.  
     
     
         10 . The method of  claim 8 , wherein converting the deposited SiGe layer to a strain-relaxed single crystal SiGe layer comprises implanting a bubble forming agent below the interface between the first Si layer and the deposited SiGe layer.  
     
     
         11 . The method of  claim 10 , wherein the bubble forming agent is selected from the group consisting of He and H.  
     
     
         12 . The method of  claim 11 , wherein converting the deposited SiGe layer additionally comprises annealing the SiGe layer.  
     
     
         13 . The method of  claim 6 , wherein converting the deposited SiGe layer to a strain-relaxed single crystal SiGe layer comprises: 
 disrupting the interface between the first Si layer and the deposited SiGe layer before depositing the deposited SiGe layer; and    conducting solid phase epitaxy.    
     
     
         14 . The method of  claim 13 , wherein the interface is disrupted by the presence of up to a half monolayer of oxide on the first Si layer.  
     
     
         15 . The method of  claim 13 , wherein the interface is disrupted by the presence of up to a monolayer of dopant at the interface between the first Si layer and the deposited SiGe layer.  
     
     
         16 . The method of  claim 13 , wherein the interface is disrupted by the presence of misfit dislocations.  
     
     
         17 . The method of  claim 6 , wherein: 
 the first Si layer is part of a silicon-on-insulator substrate; and    converting the deposited SiGe layer to a strain-relaxed single crystal SiGe layer comprises melting the deposited SiGe layer.    
     
     
         18 . The method of  claim 17 , wherein melting comprises diffusing germanium from the deposited SiGe layer through the first Si layer to an oxide interface.