Thin wafer detectors with improved radiation damage and crosstalk characteristics
View Patent ↗The present invention provides for reduced radiation damage susceptibility, decreased affects of crosstalk, and increased flexibility in application. In one embodiment, the present invention includes a back side illuminated photodiode array with a back side etching that minimizes the active area layer, thereby decreasing the affects of crosstalk. The back side etching is preferably, but by no way of limitation, in the form of “U” or “V” shaped grooves. The back side illuminated with back side etching (BSL-BE) photodiodes are implemented in an array and have superior performance characteristics, including less radiation damage due to a thinner active area, and less crosstalk due to shorter distances for minority carriers to diffuse to the PN junction.
1. A photodiode array comprising:
a substrate having at least a front side and a back side;
a plurality of photodiodes integrally formed in the substrate forming said array;
a plurality of metal contacts provided on said front side, wherein the fabrication of said array comprises:
diffusing a n+ layer on said back side of said substrate forming a deep n+ region;
applying a first masking layer on said back side;
applying a second masking layer on said back side;
applying a photoresist mask on said back side, forming an etching pattern;
first etching said second masking layer according to said photoresist mask pattern;
second etching said first masking layer according to said photoresist mask pattern;
removing said photoresist mask;
third etching said deep n+ region and said substrate, forming grooves in said substrate;
diffusing a n+ layer onto said back side of said substrate, forming a shallow n+ region; and
coating said back side of said substrate with an antireflective coating,
wherein said first masking layer, said second masking layer, and said antireflective coating form a three-layer dielectric membrane and wherein said membrane forms a bridge between said grooves in said back side.
2. The array of claim 1 , wherein said antireflective coating layer is silicon dioxide.
3. A photodiode array comprising:
a substrate having at least a front side and a back side;
a plurality of photodiodes integrally formed in the substrate forming said array;
a plurality of metal contacts provided on said front side, wherein the fabrication of said array comprises:
diffusing a n+ layer on said back side of said substrate forming a deep n+ region;
applying a first masking layer on said back side;
applying a second masking layer on said back side;
applying a photoresist mask on said back side, forming an etching pattern;
first etching said second masking layer according to said photoresist mask pattern;
second etching said first masking layer according to said photoresist mask pattern;
removing said photoresist mask;
third etching said deep n+ region and said substrate, forming grooves in said substrate;
diffusing a n+ layer onto said back side of said substrate, forming a shallow n+ region; and
coating said back side of said substrate with an antireflective coating wherein a handle wafer is bonded to said front side.
4. The array of claim 3 , wherein front surface cathode and anode contacts are brought to a surface of said handle wafer via metallization of channels.
5. The array of claim 4 , wherein said channels are formed from side walls of said handle wafer.
6. The array of claim 5 , wherein said side walls forming said channels comprise a first layer and a second layer.
7. The array of claim 6 , wherein said first layer comprises an oxide insulation layer.
8. The array of claim 6 , wherein said second layer comprises a heavily doped pad layer of a selected conductivity type of either p+ doped or n+ doped.
9. A photodiode array comprising:
a substrate having at least a front side and a back side;
a plurality of photodiodes integrally formed in the substrate forming said array;
a plurality of metal contacts provided on said front side, wherein the fabrication of said array comprises:
applying a first masking layer on said back side;
applying a second masking layer on said back side;
applying a photoresist mask on said back side, forming an etching pattern;
first etching said second masking layer according to said photoresist mask pattern;
second etching said first masking layer according to said photoresist mask pattern;
removing said photoresist mask;
third etching said substrate, forming grooves in said substrate;
diffusing a shallow n+ layer onto said back side of said substrate, forming a shallow n+ region; and
coating said back side of said substrate with an antireflective coating wherein said membrane forms a bridge between said grooves in said back side.
10. The array of claim 9 , wherein said antireflective coating layer is silicon dioxide.
11. A photodiode array comprising:
a substrate having at least a front side, a back side, and a handle wafer bonded to said front side;
a plurality of photodiodes integrally formed in the substrate forming said array; and
a plurality of electrical contacts in electrical communication with said front side, wherein front surface cathode and anode contacts are brought to a top surface of said handle wafer via metallization of channels wherein said channels are formed from side walls of said handle wafer and wherein said channels connect a p+ metal pad to the p+ region and an n+ metal pad to the n+ region.
12. The array of claim 11 , wherein said side walls of said handle wafer comprise a first layer and a second layer.
13. The array of claim 12 , wherein said first layer comprises an oxide.
14. The array of claim 12 , wherein said second layer is boron doped polysilicon.
15. The array of claim 12 , wherein said second layer is phosphorus doped polysilicon.
16. The array of claim 12 , wherein said second layer is a p+ metal pad.
17. The array of claim 12 , wherein said second layer is an n+ metal pad.