Fixed-Pattern Noise Induced by Transmission Gate in Pinned 4T CMOS Image Sensor Pixels

In this paper, we present the characterization and analysis of fixed-pattern noise (FPN) in CMOS image sensor (CIS) pixels fabricated in CMOS 0.18-mum process. The experimental results demonstrate that the dark signal degradation of pinned 4T CIS is mainly due to the dark current generated from the transmission gate (TG) instead of the photodiode (PD). From our investigations of gate voltage/charge transfer time - dark current characterization and temperature dependencies, we found that hot-carrier (H-C) induced impact ionization and trap-induced leakage current are the main mechanism of sensor performance degradation