[OPTICAL REVIEW Vol. 12, No. 3 (2005) 196-201]
© 2005 The Optical Society of Japan

A 64 × 64 CMOS Active Pixel Sensor Operative at a Very Low Illumination Level

Jae-Hyoun PARK1,2, Hoon KIM1, Sang-Ho SEO2 and Jang-Kyoo SHIN2*

1NANO Scale Quantum Devices Research Center, Korea Electronics Technology Institute, #455-6 Masan-ri, Jinwi-myon, Pyoungteak, Kyunggi-do 451-865, Korea
2Department of Electronics, Kyungpook National University, 1370 Sankyuk-dong, Buk-ku, Deagu 702-701, Korea

(Received June 21, 2004; Accepted March 25, 2005)

A CMOS image sensor that focuses on very low illumination applications is described. The sensor uses a 0.35 μm 2-poly 4-metal standard CMOS process and is realized as a 64 × 64 array of 7.8 × 7.4 μm2 active pixels with a fill factor of 33%. The unit pixel contains 3 NMOSFETs and a gate-body tied PMOSFET photodetector. The image sensor features highly sensitive characteristics because of the photodetector which has a maximum photo-responsivity of 2.5 × 102 A/W, and a pixel configuration with a voltage gain of about 1.3 and a pixel sensitivity of 1.2 × 10 V/lx·s. Furthermore, this sensor has a well-defined output voltage at a very low illumination level of sub-10 lx, such as with a photo-sensitivity of 35 mV/lx without adjusting gain and integration time.

Key words: CMOS image sensor, active pixel, PMOSFET photodetector, low illumination

*E-mail: jkshin@ee.knu.ac.kr