LOW VOLTAGE SOI CMOS IMAGE SENSOR WITH PINNED PHOTODIODE ON HANDLE WAFER

Abstract

We have fabricated 32 × 32 SOI CMOS active pixel image sensor with pinned photodiode on handle wafer in order to reduce dark current, transfer charge completely, and improve spectral response. The four transistor type active pixel image sensor is comprised of reset and source follower transistors on SOI seed wafer, while the pinned photodiode, transfer gate, and floating diffusion are fabricated on SOI handle wafer. The pinned photodiode could be optimized because the process of the photodiode on SOI handle wafer is independent of the transistor process on SOI seed wafer. The optimized pinned photodiode is simulated in order to understand complete charge transfer at 3.3 V and 2.5 V of transfer gate voltage, respectively. We also investigated the optical response of fabricated active pixel image sensor under different illumination density conditions from He - Ne laser source at 3.3 V and 2.5 V of transfer gate voltage.