Thin Active Layer Fishbone Photodiode With A Shallow N+ Layer and Method of Manufacturing the Same

Abstract

The present invention is directed toward a detector structure, detector arrays, and a method of detecting incident radiation. The present invention comprises a photodiode array and method of manufacturing a photodiode array that provides for reduced radiation damage susceptibility, decreased affects of crosstalk, reduced dark current (current leakage) and increased flexibility in application.

We claim: 
     
         1 . A photodiode array comprising:
 a thin active layer substrate having at least a front side and a back side;   a plurality of photodiodes integrally formed in the thin active layer substrate forming said array;   a plurality of metal contacts provided on said front side, wherein the fabrication of said array comprises:
 coating said front side and said back side of said substrate with an oxide layer via mask oxidation; 
 coating said front side of said substrate with a photoresist layer; 
 masking said front side of said substrate with a p+ lithography mask; 
 selectively etching the oxide layer on said front side said substrate wafer, wherein the p+ lithography mask is used to reveal p+ diffusion regions on said front side and etching the oxide coating on said back side of said substrate completely; 
 diffusing a p+ layer on said front side of said substrate forming p+ diffusion regions; 
 applying a drive-in oxidation layer on said front side of said substrate; 
 coating said front side of said substrate with a photoresist layer; 
 masking said front side of said substrate with a n+ lithography mask to form at least one active area etch pattern; 
 selectively etching the photoresist layer on said front side of said substrate using said active area etch pattern to reveal n+ diffusion regions on said front side; 
 diffusing a n+ layer on said front side of said substrate forming shallow n+ regions between adjacent p+ regions; 
 performing a drive-in oxidation on said front side of said substrate; 
 coating at least one exposed surface on said front side of said substrate with an oxide layer; 
 coating said front side of said substrate with a silicon nitride layer; 
 coating said front side of said substrate with a photoresist layer; 
 masking said front side of said substrate wafer using a contact window mask; 
 selectively etching the front side of the substrate using said contact window mask to form at least one contact window; 
 metallizing said front side and said back side of said substrate; 
 coating said front side of said substrate with a photoresist layer; and 
 masking and selectively etching said front side of said substrate to form metal contacts. 
   
     
     
         2 . The array of  claim 1 , wherein said thin active layer has a thickness of 15 μm. 
     
     
         3 . The array of  claim 1 , wherein said p+ mask pattern is a fishbone pattern. 
     
     
         4 . The array of  claim 3  wherein the fishbone pattern p+ mask comprises a plurality of p+ bones further defined by a p+ periphery frame bone. 
     
     
         5 . The array of  claim 4  wherein the distance between adjacent p+ bones in said fishbone pattern is 700 μm. 
     
     
         6 . The array of  claim 1 , wherein said shallow n+ layer has a depth of 0.3 μm. 
     
     
         7 . The array of  claim 1 , wherein said antireflective coating layer is a thin film material. 
     
     
         8 . The array of  claim 7  wherein said thin film material is one of an oxide, a sulfide, a fluoride, a nitride, a selenide, or a metal. 
     
     
         9 . The array of  claim 7  wherein said antireflective coating is a silicon dioxide antireflective having a thickness of 150 Å. 
     
     
         10 . The array of  claim 7  wherein said antireflective coating is a silicon nitride antireflective having a thickness of 425 Å. 
     
     
         11 . The array of  claim 1  wherein an oxide layer is retained on at least a portion of the front side of the thin active layer to increase the structural rigidity of the device. 
     
     
         12 . The array of  claim 1  further comprising a mechanical support bonded to said back side of said thin active area layer substrate. 
     
     
         13 . The array of  claim 12  wherein the mechanical support comprises n+ silicon substrate. 
     
     
         14 . A photodiode array comprising:
 a thin active area substrate having at least a front side and a back side;   a plurality of diode elements integrally formed in the substrate forming said array, wherein each diode element has a p+ fishbone pattern on said front side, further comprising at least two p+ bones, a p+ bone frame periphery, and at least one shallow n+ region between adjacent p+ regions and wherein each p+ bone is protected by a thick oxide layer, and   a plurality of front surface cathode and anode contacts,   wherein said at least one shallow n+ region increases the stability of the diode element relative to a diode element without said shallow n+ region.   
     
     
         15 . The array of  claim 14 , wherein said thin active layer has a thickness of 15 μm. 
     
     
         16 . The array of  claim 14 , wherein said p+ mask pattern is a fishbone pattern. 
     
     
         17 . The array of  claim 14  further comprising a mechanical support bonded to said back side of said thin active area layer substrate 
     
     
         18 . A photodiode array comprising:
 a thin active area substrate having at least a front side and a back side;   a mechanical support bonded to said back side of said thin active area substrate;   a plurality of diode elements integrally formed in the substrate forming said array, wherein each diode element has a p+ fishbone pattern on said front side, further comprising at least two p+ bones, a p+ bone frame periphery, and at least one shallow n+ region between adjacent p+ regions and wherein each p+ bone is protected by a thick oxide layer, and   a plurality of front surface cathode and anode contacts,   wherein said at least one shallow n+ region increases the stability of the diode element relative to a diode element without said shallow n+ region.   
     
     
         19 . The array of  claim 18 , wherein said thin active layer has a thickness of 15 μm. 
     
     
         20 . The array of  claim 18 , wherein said p+ mask pattern is a fishbone pattern.