A Novel CMOS Photon Sensing Device With Dark Current Cancellation and Dynamic Sensitivity

• Main Authors: Hsiu-Yu Cheng, 鄭秀渝
• Other Authors: Ya-Chin King
• Format: Others
• Language: en_US
• Published: 2002
• Online Access: http://ndltd.ncl.edu.tw/handle/34764373795294838026

碩士 === 國立清華大學 === 電子工程研究所 === 90 === An ultra low dark signal and high sensitivity pixel has been developed for an embedded active-pixel CMOS image sensor, by using a standard 0.35-µm CMOS logic process. To achieve in-pixel dark current cancellation, we developed a combined photogate/photodiode photon-sensing device with a novel operation scheme. To eliminate the photosensitivity reduction resulting from the optically opaque salicide layer, a salicide blocking mask is adopted to obtain a sensitivity improvement of 110%. The experimental results demonstrate that the severe dark signal degradation of CMOS active pixel sensor (APS) is reduced more than an order of magnitude. Through varying the bias conditions on the photogate, dynamic sensitivity can be obtained by increasing the maximum allowable illumination level. Combining the above two operation schemes, the dynamic range of this new cell is extended by more than 20X.