Investigation of leakage current in pinned photodiode CMOS imager pixel with negative transfer-gate bias operation

The characteristics of leakage current observed in the pixels of pinned photodiode CMOS image sensor with negative transfer-gate bias operation are investigated, taking metal contamination into account. Simulation results show that interface states between insulator and the pinned layer in the vicinity of transfer gate, acting as hole traps, are responsible for negative transfer-gate bias dependence of the dark current.