Research And Improvement On Photo-Gate CMOS Image Sensor In-Pixel Structure

CMOS image sensor has developed very fast during the past ten years because of its advantages of low cost, low power dissipation, high integration, being compatible with standard CMOS process, random access and so on. There are three types of CMOS image sensor in-pixel structures which are used now. Among them, photo-gate CMOS image senor has the advantages of simple structure and low dark current, and has attracted extensive attention. But the short wavelength response in this type of CMOS image sensor has limited its application. To overcome the negative factor, a new in-pixel structure of photo-gate CMOS image sensor has been proposed here. While maintaining the dark current and crosstalk at similar level as those of the original structure, the new structure with inverted gate is shown to reduce the short wavelength response effectively. Based on the standard 0.35μm CMOS process, the new in-pixel structure of photo-gate CMOS image sensor has been proved to have better short wavelength response by simulation with Synopsys's Medici two-dimensional device simulator. So, a more effective method has been developed here to suppress the short wavelength response of photo-gate CMOS image sensor, which can widen its application field greatly.