Reduction of Random Noise in Complementary Metal Oxide Semiconductor Image Sensors by Gate Oxide Interface Control

Abstract

Techniques to reduce random noise in complementary metal oxide semiconductor (CMOS) image sensor chips with pixel sizes as small as 2.2 ×2.2 µm2 are addressed. By applying dummy heat annealing and plasma nitrided (PN) oxide, random noise can be reduced by more than 40%. Measured results indicate that the gate oxide–Si interface is improved by a dummy heat treatment, and PN oxide is a good choice as a gate oxide for image sensors, since it has an optimal nitrogen profile as a gate oxide while it effectively suppresses boron penetration. The results show the importance of nitrogen profile control in gate oxides and of oxide curing for low noise characteristics in CMOS image sensors.