Germanium-silicon light sensing apparatus

Abstract

A method for fabricating an image sensor array having a first group of photodiodes for detecting light at visible wavelengths a second group of photodiodes for detecting light at infrared or near-infrared wavelengths, the method including growing a germanium-silicon layer on a semiconductor donor wafer; defining pixels of the image sensor array on the germanium-silicon layer; defining a first interconnect layer on the germanium-silicon layer, wherein the interconnect layer includes a plurality of interconnects coupled to the first group of photodiodes and the second group of photodiodes; defining integrated circuitry for controlling the pixels of the image sensor array on a semiconductor carrier wafer; defining a second interconnect layer on the semiconductor carrier wafer, wherein the second interconnect layer includes a plurality of interconnects coupled to the integrated circuitry; and bonding the first interconnect layer with the second interconnect layer.

What is claimed is: 
     
         1 . A method for fabricating an image sensor array, the method comprising:
 forming, on a semiconductor donor wafer comprising silicon, one or more recesses;   growing, on the one or more recesses, an absorption layer comprising germanium;   forming a first interconnect layer on the absorption layer, the first interconnect layer comprising a plurality of interconnects configured to be coupled to the absorption layer;   forming, on a semiconductor carrier wafer, integrated circuitry for controlling the image sensor array;   forming the integrated circuitry, forming a second interconnect layer on the semiconductor carrier wafer, the second interconnect layer comprising a plurality of interconnects coupled to the integrated circuitry; and   bonding the first interconnect layer with the second interconnect layer.   
     
     
         2 . The method of  claim 1 , further comprising:
 after bonding the first interconnect layer with the second interconnect layer, removing a portion of the semiconductor donor wafer.   
     
     
         3 . The method of  claim 2 , wherein removing the portion of the semiconductor donor wafer comprises polishing the semiconductor donor wafer. 
     
     
         4 . The method of  claim 1 , wherein growing, on the one or more recesses, the absorption layer comprises:
 growing the germanium on the one or more recesses by a selective epitaxial growth, such that the germanium is at least partially embedded in the one or more recesses.   
     
     
         5 . The method of  claim 4 , wherein growing, on the one or more recesses, the germanium further comprises:
 polishing the absorption layer to planarize the germanium to be fully embedded in the one or more recesses.   
     
     
         6 . The method of  claim 1 , further comprising:
 after forming the one or more recesses, forming, within the one or more recesses, one or more sidewall spacers.   
     
     
         7 . The method of  claim 6 , wherein forming the one or more sidewall spacers comprises:
 depositing, on the semiconductor donor wafer, a dielectric layer; and   performing a directional etch of the dielectric layer.   
     
     
         8 . The method of  claim 1 , further comprising:
 forming lens elements over the image sensor array, wherein each of the lens elements is arranged to guide light to a respective photodiode of the image sensor array, and   forming wavelength filters over the image sensor array, wherein each of the wavelength filters is configured to filter light for a respective photodiode of the image sensor array.   
     
     
         9 . The method of  claim 1 , wherein each of the one or more recesses corresponds to a pixel in the image sensor array. 
     
     
         10 . The method of  claim 1 , wherein a shape of each of the one or more recesses comprises a square or a circle.