Method for Manufacturing a Semiconductor Substrate

Abstract

A method for manufacturing a semiconductor substrate includes providing a first wafer having a first surface and a second surface opposite the first surface, forming cavities in the first wafer at a first distance from the first surface, wherein the cavities, when seen in a cross-section perpendicular to the first surface, are laterally spaced from each other by partition walls formed by the semiconductor material of the first wafer, the cavities forming a separation region, bonding a second wafer on the first surface of the first wafer, breaking the partition walls by applying mechanical impact to the partition walls to split the first wafer along the separation region so that a residual wafer remains attached to the second wafer, and depositing an epitaxial layer on the residual wafer.

What is claimed is: 
     
         1 . A method for manufacturing a semiconductor substrate, the method comprising:
 providing a seed-wafer having a first surface and a second surface opposite the first surface, the seed-wafer comprising a first semiconductor material exposed at the first surface of the seed-wafer;   forming, when seen in a cross-section perpendicular to the first surface, cavities in the seed-wafer at a first distance from the first surface, the cavities being laterally spaced from each other by partition walls formed by the first semiconductor material of the seed-wafer, the cavities forming a separation region;   depositing, at an elevated temperature, a second semiconductor material different to the first semiconductor material on the exposed first semiconductor material of the seed-wafer, the second semiconductor material having a thickness which is at least 10-times larger than the first distance between the cavities and the first surface of the seed-wafer; and   cooling the seed-wafer with the second semiconductor material deposited on the first surface of the seed-wafer to cause mechanical stress acting on the partition walls due to different thermal shrinkage of the first semiconductor material and the second semiconductor material, wherein the mechanical stress results in breaking of at least some of the partition walls to split at least partially the seed-wafer along the separation region.   
     
     
         2 . The method of  claim 1 , wherein the cavities are spaced from the second surface of the seed-wafer by a second distance which is at least 10-times larger than the first distance. 
     
     
         3 . The method of  claim 1 , wherein the partition walls between adjacent cavities have a lateral thickness d and the cavities have a height b, wherein the ratio b:d is 5:1 or less. 
     
     
         4 . The method of  claim 3 , wherein the ratio b:d is 3:1 or less. 
     
     
         5 . The method of  claim 1 , wherein the cavities have a height b and a lateral width c, wherein the ratio c:b is between about 10:1 and about 100:1. 
     
     
         6 . The method of  claim 1 , wherein, when seen in a projection onto the first surface of the seed-wafer, the cavities are ring-shaped and arranged in a substantially concentric manner. 
     
     
         7 . The method of  claim 1 , wherein forming the cavities comprises:
 forming a plurality of groups of closely spaced trenches in the first surface of the seed-wafer, the trenches extending at least to a depth from the first surface corresponding to the first distance; and   tempering the seed-wafer at an elevated temperature in a deoxidising atmosphere to cause surface migration of the first semiconductor material of the seed-wafer until the trenches of the respective groups of closely spaced trenches coalesce to respective cavities.   
     
     
         8 . The method of  claim 7 , wherein the elevated temperature is between about 1000° C. and about 1150° C. 
     
     
         9 . The method of  claim 1 , wherein the first semiconductor material is silicon and the second semiconductor material is one of GaN, sapphire, and SiC. 
     
     
         10 . The method of  claim 1 , wherein a residual wafer remains attached to the epitaxial layer after breaking of the partition walls, the method further comprising:
 removing the residual wafer from the epitaxial layer.   
     
     
         11 . The method of  claim 1 , further comprising:
 integrating at least one semiconductor device into the epitaxial layer after splitting the seed-wafer by forming at least one doping region.   
     
     
         12 . A method for manufacturing a semiconductor substrate, the method comprising:
 providing a first wafer having a first surface and a second surface opposite the first surface;   forming cavities in the first wafer at a first distance from the first surface, wherein the cavities, when seen in a cross-section perpendicular to the first surface, are laterally spaced from each other by partition walls formed by the semiconductor material of the first wafer, the cavities forming a separation region;   bonding a second wafer on the first surface of the first wafer;   breaking the partition walls by applying mechanical impact to the partition walls to split the first wafer along the separation region so that a residual wafer remains attached to the second wafer; and   depositing an epitaxial layer on the residual wafer.   
     
     
         13 . The method of  claim 12 , further comprising:
 at least partially integrating semiconductor devices in the epitaxial layer by forming doping regions in the epitaxial layer.   
     
     
         14 . The method of  claim 13 , further comprising:
 polishing the residual wafer prior to depositing the epitaxial layer.   
     
     
         15 . The method of  claim 13 , wherein the cavities are interconnected with each other, the method further comprising:
 filling the cavities with an aqueous solution having a freezing point; and   breaking the partition walls by cooling the aqueous solution in the cavities below the freezing point to cause expansion of the aqueous solution.   
     
     
         16 . The method of  claim 15 , further comprising:
 forming a hydrophilic layer on internal surfaces of the cavities prior to filling the cavities with the aqueous solution.   
     
     
         17 . The method of  claim 13 , wherein the cavities are interconnected with each other, the method further comprising:
 filling the cavities with an aqueous solution; and   breaking the partition walls by subjecting the aqueous solution in the cavities to ultrasonic sound to cause cavitation of the aqueous solution.   
     
     
         18 . The method of  claim 13 , wherein the second wafer comprises a bonding layer, wherein bonding the second wafer on the first surface of the first wafer comprises:
 bonding the second wafer with its bonding layer on the first surface of the first wafer.