Integrate stressor with ge photodiode using a substrate removal process

Abstract

The embodiments of the present disclosure describe a stressed Ge PD and fabrications techniques for making the same. In one embodiment, a stressor material is deposited underneath an already formed Ge PD. To do so, wafer bonding can be used to bond the wafer containing the Ge PD to a second, handler wafer. Doing so provides support to remove the substrate of the wafer so that a stressor material (e.g., silicon nitride, diamond-like carbon, or silicon-germanium) can be disposed underneath the Ge PD. The stress material induces a stress or strain in the crystal lattice of the Ge which changes its bandgap and improves its responsivity.

We claim: 
     
         1 . A germanium photodetector, comprising:
 a first layer;   germanium disposed on the first layer, wherein the first layer and the germanium are doped to form a PIN junction; and   a stressor material disposed on an opposite side of the first layer as the germanium, wherein the stressor material induces a stress that changes an optical absorption edge of the germanium, and wherein the germanium and the stressor material directly contact respective sides of the first layer.   
     
     
         2 . The germanium photodetector of  claim 1 , wherein the first layer comprises a semiconductor material. 
     
     
         3 . The germanium photodetector of  claim 2 , wherein the semiconductor material is crystalline silicon. 
     
     
         4 . The germanium photodetector of  claim 1 , further comprising:
 a pair of contacts establishing electrical connections with respective doped regions of the first layer; and   a first contact establishing an electrical connection to a doped region of the germanium.   
     
     
         5 . The germanium photodetector of  claim 1 , further comprising:
 side stressor material disposed on at least two sides of the germanium, and on the first layer, wherein the side stressor material induces a stress that changes the optical absorption edge of the germanium.   
     
     
         6 . The germanium photodetector of  claim 1 , further comprising:
 a top stressor material disposed on a first side of the germanium that is opposite a second side of the germanium that faces the stressor material, wherein the top stressor material induces a stress that changes the optical absorption edge of the germanium.   
     
     
         7 . The germanium photodetector of  claim 1 , wherein the stressor material comprises silicon nitride. 
     
     
         8 . The germanium photodetector of  claim 1 , wherein the stressor material has a width that is equal to or greater than a width of the germanium. 
     
     
         9 . A germanium photodetector, comprising:
 a first layer, wherein the first layer comprises two doped regions, and a pair of contacts establishes electrical connections between the two doped regions of the first layer and their respective metal portions;   germanium disposed on the first layer, wherein the germanium comprises a doped region, a first contact establishes an electrical connection between the doped region of the germanium and a first metal portion, and the first layer and the germanium are doped to form a PIN junction; and   a stressor material disposed on an opposite side of the first layer as the germanium, wherein the stressor material induces a stress that changes an optical absorption edge of the germanium.   
     
     
         10 . The germanium photodetector of  claim 9 , wherein the germanium and the stressor material directly contact respective sides of the first layer. 
     
     
         11 . The germanium photodetector of  claim 9 , wherein the first layer comprises a semiconductor material. 
     
     
         12 . The germanium photodetector of  claim 11 , wherein the semiconductor material is crystalline silicon. 
     
     
         13 . The germanium photodetector of  claim 9 , further comprising:
 side stressor material disposed on at least two sides of the germanium, and on the first layer, wherein the side stressor material induces a stress that changes the optical absorption edge of the germanium.   
     
     
         14 . The germanium photodetector of  claim 9 , further comprising:
 a top stressor material disposed on a first side of the germanium that is opposite a second side of the germanium that faces the stressor material, wherein the top stressor material induces a stress that changes the optical absorption edge of the germanium.   
     
     
         15 . The germanium photodetector of  claim 10 , wherein the stressor material comprises silicon nitride. 
     
     
         16 . The germanium photodetector of  claim 10 , wherein the stressor material has a width that is equal to or greater than a width of the germanium. 
     
     
         17 . A germanium photodetector, comprising:
 a first layer;   germanium disposed on the first layer, wherein the first layer and the germanium are doped to form a PIN junction;   a stressor material disposed on an opposite side of the first layer as the germanium, wherein the stressor material induces a stress that changes an optical absorption edge of the germanium; and   a side stressor material disposed on at least two sides of the germanium, and on the first layer, wherein the side stressor material induces a stress that changes the optical absorption edge of the germanium.   
     
     
         18 . The germanium photodetector of  claim 17 , wherein the germanium and the stressor material directly contact respective sides of the first layer. 
     
     
         19 . The germanium photodetector of  claim 17 , further comprising:
 a pair of contacts establishing electrical connections with respective doped regions of the first layer; and   a first contact establishing an electrical connection to a doped region of the germanium.   
     
     
         20 . The germanium photodetector of  claim 17 , further comprising:
 a top stressor material disposed on a first side of the germanium that is opposite a second side of the germanium that faces the stressor material, wherein the top stressor material induces a stress that changes the optical absorption edge of the germanium.