Low-leakage-current and low-operating-voltage buried photodiode for a CMOS imager

A low-leakage current and low-operating-voltage buried-photodiode structure of CMOS image sensors has been developed. The new structure adopted a modified fabrication process as well as an additional shallow p+ layer structure that covers the entire surface of the deep n-type photodiode. The required operating voltage for complete charge transfer from the photodiode is 3.3 V. Furthermore, the leakage current level allows high-quality images comparable to those of CCD image sensors.