High sensitivity and high dynamic-range CMOS image sensor pixel structure with dynamic C-V characteristics

Abstract

A new photogate pixel structure for high performance CMOS Image Sensors is proposed. A new photogate structure is incorporated into the photodiode active-pixel structure. The proposed pixel structure exhibits the dynamic integration capacitance characteristics, which can be controlled by varying the control-voltage at the photogate node. Since the sensitivity is inversely proportional to the integration capacitance, the dynamic integration capacitance characteristics can provide the new functionality and controllability for high sensitivity and high dynamic range. At a low voltage level of the photogate, the pixel sensitivity of the new photogate pixel structure is maximized due to the minimum value of the integration capacitance. At a high voltage of the photogate, the dynamic range of the new structure can be maximized due to the increased well capacity. In addition, at an optimum bias voltage of the photogate, both the dynamic-range and the sensitivity can be simultaneously improved. Consequently, the new pixel structure allows performance tunability as well as optimization in both the dynamic range and the sensitivity of the image sensor cell.