Broad spectral response of large array CIS with BSI-PD from visible light to near ultraviolet

Abstract

The narrow spectral response range of traditional CMOS image sensors (CISs) limits their application such as weak-light and ultraviolet (UV) scenes. In the paper, a novel method of broadening spectral response range of traditional CISs is proposed by the design of a wide-PN photodiode (PD), which can be achieved by both back-illuminated (BSI) and gradient-doping structure using traditional process. Theoretical research shows that the wide-PN junction near illuminated surface can broaden the spectral range of the BSI-PD from visible light to near UV, which is conducive to weak-light imaging due to the generation of more photogenerated electrons. Moreover, the gradient potential in the BSI-PD with gradient-doping can inhibit the recombination of photogenerated electron-hole pairs, leading to the improvement of QE. The above BSI-PD is used for a large array CIS with 8520 × 9448 pixels, which was taped out by 110 nm CMOS process. The testing results indicate the large array CIS has a good imaging effect in different scenes.