CMOS image sensor: Process impact on dark current

Abstract

Dark current is a major concern for the CMOS Image sensor. If the Shockley-Read-Hall generation creates this current, the origin of defects is multiple. Metallic contaminants cause deep level bulk defects, this gives the blemish pixels. The interface states generate the mean dark current of the pixel. The good use of Forming Gas anneal is needed to passivate these interfaces. Next, all the plasma processes have to be optimized not to dissociate the passivation, because of the deep UV and the electric field created by plasma. Finally, some process improvements, or the choice of a p-type pixel with holes collection, should give robust image sensors with low and controlled dark current.