A Highly Ultraviolet Light Sensitive and Highly Robust Image Sensor Technology Based on Flattened Si Surface

In this paper, an ultraviolet light (UV-light) sensitive and highly robust Si photodiode technology based on atomically flattened Si surface is summarized and its application to a CMOS image sensor is demonstrated. By forming a surface high concentration layer of photodiode with steep dopant profile uniformly on flattened Si surface, the almost 100 % internal quantum efficiency to UV-light waveband and negligibly small degradation of photo-sensitivity were achieved for both n+pn and p+np photodiodes. The developed photodiode technology was applied to a 5.6 μm pixel pitch front-side-illuminated CMOS image sensor. The fabricated sensor chip exhibited a spectral response to a wide light waveband of 200-1000 nm, and the sensitivity degradation did not occur after the strong UV-light exposure stress.