Technology and System Integration of CMOS Image Sensors

The major drawback of the CMOS image sensors when compared to CCD devices is reduced image quality at low illumination due to lower quantum efficiency and larger leakage current of the CMOS photodiodes. In this paper, a novel photodiode structure is presented. Only minor changes to the original CMOS process were applied that don't affect the parameters of other devices. The quantum efficiency of the novel photodiode was nearly doubled and the leakage current was decreased by almost 2 orders of magnitude with respect to a source/drain junction photodiode. The concept is expected to be also applicable to future CMOS processes. This makes the benefits of the system integration of sensor and signal processing on a single CMOS chip available to applications requiring good image quality at low-light levels.