Abstract: Ultra thin back-illuminated photodiode array fabrication methods providing backside contact by diffused regions extending through the array substrate. In accordance with the methods, a matrix is diffused into one surface of a substrate, and at a later stage of the substrate processing, the substrate is reduced in thickness and a similar matrix is diffused into the substrate from the other side, this second diffusion being aligned with the first and contacting the first within the substrate. These two contacting matrices provide good electrical contact to a conductive diffusion on the backside for a low resistance contact to the backside. Various embodiments are disclosed.

Abstract: Fast silicon photodiodes with high back surface reflectance in a wavelength range close to the bandgap, and methods of fabrication of such photodiodes. The photodiodes have a patterned oxide or nitride layer on the back surface covered by a metal layer that makes electrical contact with the substrate in a pattern complimentary to the pattern of the oxide or nitride layer. This provided high reflectivity over a large percentage of the back surface, while at the same time providing excellent electrical contact to the back surface.