A pixel size shrinkage of amplified MOS imager with two-line mixing

This paper describes a pixel size shrinkage of an amplified MOS image sensor (AMI). We have developed a new circuit technique to achieve the reduction of a pixel size while realizing vertical two-line mixing and high sensitivity. A 1/4-in format 250-k pixel image sensor was developed using a 0.8-μm CMOS process. The difference from the conventional CMOS process is an additional layer of ion-implantation process. The power supply voltages of this imager are 4 and 6 V. The dynamic range of 75 dB, the sensitivity of 1.8 μA/Ix, and the smear noise of less than -120 dB have been attained for the pixel size of 7.2 (H)×5.6 (V) μm². Although the measured fixed pattern noise ratio (FPN) of this imager is -55 dB, analysis with a test chip shows that FPN can be improved by 2 dB by adopting a suitable gate length for amplifier and resetting MOSFET, respectively