A new well capacity adjusting scheme for high sensitivity, extended dynamic range CMOS imaging pixel sensors

Abstract

An embedded 3T active-pixel complementary metal oxide semiconductor (CMOS) image sensor, fabricated with a standard 0.25-μm CMOS logic process with new well capacity adjusting scheme is proposed to extend dynamic range. The photo-sensing device consists of a photo-gate area and a photo-diode, and the well capacity is adjusted by controlling the pulse voltage on the photo-gate. Besides, the imaging sensitivity can be improved through optimizing the photo-gate to photo-diode area ratio and the pulse high level of photo-gate voltage. The experimental results demonstrate that the pixel can achieve both high sensitivity at low illumination and extended dynamic range of 25 dB under high illumination. ©2005 The Japan Society of Applied Physics.