Decreasing dark current of complementary metal oxide semiconductor image sensors by new postmetallization annealing and ultraviolet curing

We demonstrate a new postmetallization annealing and ultraviolet (UV) treatment process for reducing the dark current of image sensors. The new method utilizes a large amount of hydrogen in a plasma-silicon nitride film (p-SiNx) as a hydrogen diffusion source. Through charge pumping measurement, it is proved that this method effectively reduces the interface trap density of pixel transistors, thereby decreasing the dark current of image sensors. Although the postetch process for removing p-SiNx films induces plasma damage during the etch step, the damage can be effectively cured by the subsequent UV annealing.