Back-illuminated Si photomultipliers: structure and fabrication methods

A back-illuminated silicon photomultiplier comprising:

• a p-type substrate having front and back sides, and a thickness of less than approximately 150 um;
• a matrix of n+ regions in the p-type substrate;
• a matrix of p+ regions under the matrix of n+ regions
• and adjacent the back side of the substrate, with the bottom of the matrix of n+ regions forming a p/n junction with the substrate or the p+ region;
• a common anode formed by a uniform p++ deposition or implantation on the back side of the substrate;
• a plurality of trenches in the back side of the substrate between the n+ regions, the trenches being filled with an opaque material;
• and
• cathode contacts coupled to each of the n+ regions.

A back-illuminated silicon photomultiplier comprising:

• a substrate of a first conductivity type having front and back sides, and a thickness of less than approximately 150 um;
• a matrix of regions of a second conductivity type in the substrate;
• a matrix of regions of the first conductivity type under the matrix of regions of the second conductivity type and adjacent the back side of the substrate, with the bottom of the matrix of regions of the second conductivity type forming a p/n junction with the substrate or the matrix of regions of the first conductivity type, the matrix of regions of the first conductivity type having a higher conductivity than the substrate;
• a common anode formed by a uniform layer of the first conductivity type of higher conductivity than the substrate on the back side of the substrate;
• a plurality of trenches in the back side of the substrate between the second conductivity type regions, the trenches being filled with an opaque material;
• and cathode contacts coupled to each of the regions of the second conductivity type.