Backside illumination image sensor having charge accumulation regions surrounded by a channel region on the surface of a vertical photodiode and preparation method thereof

Abstract

The present invention is to provide a backside illumination image sensor and a preparation method thereof. A photodiode and a channel region are surrounded by an isolation ring passing through a semiconductor substrate and an epitaxial layer; a source region and a drain region extend from a surface of the channel region to an interior of the channel region and surround a charge accumulation region, the source region and the charge accumulation region are isolated by the channel region. The preparation method of the isolation ring of the backside illumination image sensor is compatible with a conventional CMOS process flow. By multiple implantations, the photodiode and the source region are vertically distributed in the isolation ring, thus reducing the parasitic capacitance of a charge transfer tube, increasing the transfer rate, and improving the image frame rate of an image sensor chip.