標題: Optimal design of CMOS pseudoactive pixel sensor (PAPS) structure for low-dark-current and large-array-size imager applications
作者: Shih, YC
Wu, CY
電子工程學系及電子研究所
Department of Electronics Engineering and Institute of Electronics
關鍵字: CMOS imagers;dark current;optimal pseudoactive pixel sensor (OPAPS);photodiode;pn junctions
公開日期: 1-十月-2005
摘要: In this paper, a pixel structure called the optimal pseudoactive pixel sensor (OPAPS) is proposed and analyzed for the applications of CMOS imagers. The shared zero-biased-buffer in the pixel is used to suppress both dark current of photodiode and leakage current of pixel switches by keeping both biases of photodiode and parasitic pn junctions in the pixel bus at zero voltage or near zero voltage. The factor of photocurrent-to-dark-current ratio per pixel area (PDRPA) is defined to characterize the performance of the OPAPS structure. It is found that a zero-biased-buffer shared by four pixels can achieve the highest PDRPA. In addition, the column sampling circuits and output correlated double sampling circuits are also used to suppress fixed-pattern noise, clock feedthrough noise, and channel charge injection. An experimental chip of the proposed OPAPS CMOS imager with the format of 352 x 288 (CIF) has been designed and fabricated by using 0.25-mu m single-poly-five-level-metal (1P5M) N-well CMOS process. In the fabricated CMOS imager, one shared zero-biased-buffer is used for four pixels where the PDRPA is equal to 47.29 mu m(-2). The fabricated OPAPS CMOS imager has a pixel size of 8.2 x 8.2 mu m, fill factor of 42%, and chip size of 3630 x 3390 mu m. Moreover, the measured maximum frame rate is 30 frames/s and the dark current is 82 pA/cm(2). Additionally, the measured optical dynamic range is 65 dB. It is found that the proposed OPAPS structure has lower dark current and higher optical dynamic range as compared with the active pixel sensor (APS) and the conventional passive pixel sensor (PPS). Thus, the proposed OPAPS structure has high potential for the applications of high-quality and large-array-size CMOS imagers.
URI: http://dx.doi.org/10.1109/JSEN.2004.841429
http://hdl.handle.net/11536/13187
ISSN: 1530-437X
DOI: 10.1109/JSEN.2004.841429
期刊: IEEE SENSORS JOURNAL
Volume: 5
Issue: 5
起始頁: 956
結束頁: 963
顯示於類別:期刊論文


文件中的檔案:

  1. 000231772900024.pdf