Semiconductor substrate and process for producing it

Abstract

A semiconductor substrate useful as a donor wafer is a single-crystal silicon wafer having a relaxed, single-crystal layer containing silicon and germanium on its surface, the germanium content at the surface of the layer being in the range from 10% by weight to 100% by weight, and a layer of periodically arranged cavities below the surface. The invention also relates to a process for producing this semiconductor substrate and to an sSOI wafer produced from this semiconductor substrate.

1 .- 4 . (canceled)  
   
   
       5 . The process of  claim 21 , comprising the following steps, in the order given: 
 a) producing a layer containing periodically arranged recesses at the surface of a single-crystal silicon wafer, and    b) heat treating the single-crystal silicon wafer until a continuous layer consisting of single-crystal silicon has formed at the surface, with a layer of periodically arranged cavities beneath the surface,    wherein after the heat treating, a single-crystal, relaxed layer with a thickness of from 5 nm to 3 μm, which contains silicon and germanium, is deposited on the continuous layer at the surface, the germanium content at the surface of the layer being in the range from 10% by weight to 100% by weight.    
   
   
       6 . The process of  claim 21 , comprising the following steps, in the order given: 
 c depositing a layer containing silicon and germanium on the surface of a single-crystal silicon wafer, the layer being from 5 nm to 3 μm thick and having a germanium content at the surface of the layer in the range from 10% by weight to 100% by weight,    d producing a layer containing periodically arranged recesses at the surface of the single-crystal silicon wafer comprising the layer containing silicon and germanium, and    e heat treating of the single-crystal silicon wafer until a continuous, single-crystal, relaxed layer containing silicon and germanium has formed at the surface, with a layer of periodically arranged cavities beneath the relaxed layer.    
   
   
       7 . The process of  claim 5 , wherein a strained silicon layer is deposited on the surface of the layer containing silicon and germanium.  
   
   
       8 . The process of  claim 6 , wherein a strained silicon layer is deposited on the surface of the layer containing silicon and germanium.  
   
   
       9 . The process of  claim 7 , wherein the strained silicon layer is bonded to a handle wafer.  
   
   
       10 . The process of  claim 8 , wherein the strained silicon layer is bonded to a handle wafer.  
   
   
       11 . The process of  claim 9 , wherein the bonded wafers are split along the layer of cavities, so that the strained silicon layer and the layer containing silicon and germanium above it remain on the handle wafer.  
   
   
       12 . The process of  claim 10 , wherein the bonded wafers are split along the layer of cavities, so that the strained silicon layer and the layer containing silicon and germanium above it remain on the handle wafer.  
   
   
       13 . The process of  claim 11 , wherein the layer containing silicon and germanium is removed.  
   
   
       14 . The process of  claim 12 , wherein the layer containing silicon and germanium is removed.  
   
   
       15 . The process of  claim 5 , wherein the layer containing silicon and germanium is bonded to a handle wafer.  
   
   
       16 . The process of  claim 6 , wherein the layer containing silicon and germanium is bonded to a handle wafer.  
   
   
       17 . The process of  claim 15 , wherein the bonded wafers are split along the layer of cavities, so that the layer containing silicon and germanium remains on the handle wafer.  
   
   
       18 . The process of  claim 16 , wherein the bonded wafers are split along the layer of cavities, so that the layer containing silicon and germanium remains on the handle wafer.  
   
   
       19 . The process of  claim 17 , wherein a strained silicon layer is deposited on the surface of the layer containing silicon and germanium, which has remained on the handle wafer.  
   
   
       20 . The process of  claim 18 , wherein a strained silicon layer is deposited on the surface of the layer containing silicon and germanium, which has remained on the handle wafer.  
   
   
       21 . A process for producing a semiconductor substrate comprising a continuous silicon and germanium layer above a single crystal silicon wafer and separated therefrom by a layer of periodically arranged cavities, comprising the following sequences of steps, in the order given: 
 a) producing a layer containing periodically arranged recesses at the surface of a single-crystal silicon wafer, and    b) heat treating the single-crystal silicon wafer until a continuous layer consisting of single-crystal silicon has formed at the surface, with a layer of periodically arranged cavities beneath the surface,    wherein after the heat treating, a single-crystal, relaxed layer with a thickness of from 5 nm to 3 μm, which contains silicon and germanium, is deposited on the continuous layer at the surface, the germanium content at the surface of the layer being in the range from 10% by weight to 100% by weight; or    c) depositing a layer containing silicon and germanium on the surface of a single-crystal silicon wafer, the layer being from 5 nm to 3 μm thick and having a germanium content at the surface of the layer in the range from 10% by weight to 100% by weight,    d) producing a layer containing periodically arranged recesses at the surface of the single-crystal silicon wafer comprising the layer containing silicon and germanium, and    e) heat treating of the single-crystal silicon wafer until a continuous, single-crystal, relaxed layer containing silicon and germanium has formed at the surface, with a layer of periodically arranged cavities beneath the relaxed layer.