CMOS Imager with Copper Wiring and Lightpipe

Abstract

A CMOS imager technology is described, which uses Cu wiring and a polymer lightpipe. The microlens height must be optimized when using the lightpipe, so that light is focused into the top of the lightpipe rather than onto the photodiode. A SiN layer is used on the sidewalls to reflect light that enters the top of the lightpipe down onto the photodiode. The SiN layer also forms a hermetic seal, which protects the Cu wiring from ambient moisture. Using this structure, high quantum efficiency can be achieved for a 2.2 mum pixel and high reliability is demonstrated