Composite Wafer Having a SiC-Based Functional Layer

Abstract

A composite wafer includes a substrate and a SiC-based functional layer. The substrate includes a porous carbon substrate core and an encapsulating layer encapsulating the substrate core. The SiC-based functional layer comprises, at an interface region with the encapsulating layer, at least one of: a carbide and a silicide formed by reaction of a portion of the SiC-based functional layer with a carbide-and-silicide-forming metal. An amount of the carbide-and-silicide-forming metal, integrated over the thickness of the functional layer, is 10 −4 mg/cm 2 to 0.1 mg/cm 2 .

What is claimed is: 
     
         1 . A composite wafer, comprising:
 a substrate, comprising a porous carbon substrate core and an encapsulating layer, the encapsulating layer encapsulating the substrate core in an essentially oxygen-tight manner; and   a SiC-based functional layer bonded on the substrate, wherein the SiC-based functional layer comprises, at an interface region with the encapsulating layer, at least one of a carbide and a silicide formed by reaction of a portion of the SiC-based functional layer with a carbide-and-silicide-forming metal, and wherein the amount of the carbide-and-silicide-forming metal, integrated over the thickness of the functional layer, is 10 −4  mg/cm 2  to 0.1 mg/cm.   
     
     
         2 . The composite wafer of  claim 1 , wherein the interface region directly contacts the encapsulating layer without any further continuous layer in between. 
     
     
         3 . The composite wafer of  claim 1  wherein the carbide and silicide forming metal is at least one element selected from the group consisting of: Mo, Ta, Nb, V, Ti, W, Ni, and Cr. 
     
     
         4 . The composite wafer of  claim 1 , wherein the encapsulating layer is essentially oxide-tight for temperatures up to at least 1500° C. 
     
     
         5 . The composite wafer of  claim 1 , wherein the encapsulating layer comprises at least one of: SiC, a Si oxide, a Si, a Ti oxide, and Si 3 N 4 . 
     
     
         6 . The composite wafer of  claim 1 , wherein pores of the porous carbon substrate core are closed by a pore-plug material, which is different from and encapsulated by the material of the encapsulating layer. 
     
     
         7 . The composite wafer of  claim 1 , wherein the substrate has a mass density of at most 5 g/cm 3 . 
     
     
         8 . The composite wafer of  claim 1 , wherein at least a portion of the encapsulating layer connecting the side of the substrate facing the functional layer and a side of the substrate opposite to the functional layer is electrically conductive. 
     
     
         9 . The composite wafer of  claim 8 , further comprising a soldering portion on the side of the substrate opposite to the functional layer, the soldering portion being in electrical contact with the SiC functional layer. 
     
     
         10 . The composite wafer of  claim 1 , wherein no continuous layer of unreacted carbide-and-silicide-forming metal remains between the functional layer and the encapsulating layer. 
     
     
         11 . A wafer, comprising a SiC-based functional layer, wherein the SiC-based functional layer comprises, on one side, at least one of a carbide and a silicide formed by reaction of a portion of the SiC-based functional layer with a carbide-and-silicide-forming metal, and wherein the amount of the carbide-and-silicide-forming metal, integrated over the thickness of the functional layer, is 10 −4  mg/cm 2  to 0.1 mg/cm 2 . 
     
     
         12 . The wafer of  claim 11 , wherein the wafer is free of any continuous layer of non-reacted carbide-and-silicide-forming metal. 
     
     
         13 . The wafer of  claim 11 , wherein the carbide and silicide forming metal is at least one element selected from the group consisting of: Mo, Ta, Nb, V, Ti, W, Ni, and Cr. 
     
     
         14 . The wafer of  claim 11 , further comprising a soldering portion in electrical contact with the SiC functional layer. 
     
     
         15 . A composite wafer, comprising:
 a substrate, the substrate comprising a porous carbon substrate core and an encapsulating layer, the encapsulating layer comprising reactively formed SiC and encapsulating the substrate core in an essentially oxygen-tight manner; and   a SiC-based functional layer bonded on the substrate, wherein the SiC-based functional layer comprises, at an interface region to the encapsulating layer, at least one of: a carbide, a silicide, and a mixture of both.