Non-Linear Dark Current Behavior in CMOS Image Sensor

Abstract

This letter reports the non-linear dark current behavior of white spots in state-of-the-art CMOS image sensors. With continued scaling and increasing structural complexity in pinned-photodiode-based CIS, a thorough understanding of the generation mechanism of white spots is essential for developing high-performance image sensors. In this work, we investigate the non-linear dark current behavior observed in certain pixels of state-of-the-art image sensors, characterized by a decreasing carrier generation rate with increasing integration time. We attribute this behavior to the expansion of the quasi-neutral region with charge accumulation, which drives defect sites toward trap occupation, and thereby suppresses Shockley-Read-Hall generation. This mechanism is supported by a 3D analytic model and TCAD simulations.