Analysis on light transmission through Multi-Metal-Layers for CMOS image sensors

With CMOS technology's downscaling, interconnect layers are multi-stratified since the number of metal levels has increased. However, this multi-metal-layer structure above photodiodes affects sensitivity, one of a important performance, of CMOS image sensors. We proposes a method for analysis of light transmission characteristics on multi-metal-layer (interconncet layers). To evaluate the effect on the multi-metal-layer of standard CMOS process technologies, we have developed a method for calculation of the transmitted light intensity through the multi-metal-layer. We show the transmitted light intensity of calculation results for standard CMOS of 1.2μm to 22nm.