A wide dynamic range CMOS image sensor with 200-1100 nm spectral sensitivity and high robustness to UV right exposure

• Published in: Japanese Journal of Applied Physics Vol. 53; no. 4S; pp. 4 - 1-04EE07-4
• Main Authors: Nasuno, Satoshi, Kawada, Shun, Koda, Yasumasa, Nakazawa, Taiki, Hanzawa, Katsuhiko, Kuroda, Rihito, Sugawa, Shigetoshi
• Format: Journal Article
• Language: English
• Published: The Japan Society of Applied Physics 01.04.2014
• Subjects: Channels; CMOS; Dynamic range; Exposure; Pixels; Robustness; Sensors; Silicon
• ISSN: 0021-4922; 1347-4065
• DOI: 10.7567/JJAP.53.04EE07

A highly UV-light sensitive and sensitivity robust CMOS image sensor with a wide dynamic range (DR) was developed and evaluated. The developed CMOS image sensor includes a lateral overflow integration capacitor in each pixel in order to achieve a high sensitivity and a wide DR simultaneously. As in-pixel photodiodes (PDs), buried pinned PDs were formed on flattened Si surface. The PD has a thin surface p+ layer with a steep dopant concentration profile to form an electric field that drifts photoelectrons to the pinned n layer. This structure improves UV-light sensitivity and its stability. In addition, a buried channel source follower driver was introduced to achieve a low pixel noise. This CMOS image sensor was fabricated by a 0.18-µm 1-polycrystalline silicon 3-metal CMOS process technology with buried pinned PD. The fabricated image sensor has a high sensitivity for 200-1100 nm light wave band, high robustness of sensitivity and dark current toward UV-light exposure and a wide DR of 97 dB. In this paper, the PD structures, the circuit, the operation sequence and the measurement results of this CMOS image sensor are discussed.