双结光电二极管荧光检测单元暗电流优化设计

双结p+/n-well/p-sub光电二极管由于其较高灵敏度、低暗电流而成为荧光检测光电传感单元的最佳选择.文章基于0.5 μm CMOS工艺对双结p+/n-well/p-sub光电二极管进行了版图优化设计,有效减少了硅和二氧化硅界面对光电二极管光吸收区暗电流的影响.流片后测试表明优化后版图面积为100μtm×100 μm,双结p+/n-well/p-sub光电二极管单元的暗电流从11 pA减小到了6.5pA,光电流从2.15 nA稍有减弱到2.05 nA,光暗电流比值提高了60％.优化后的双结p+/n-well/p-sub光电二极管更适用于对微弱的荧光信号检测.

Dark Current Optimization of Double Junction Photoelectric Diode for Fluorescent Sensing

p+/n-well/p-sub double junction photodiode becomes the best choice for fluorescence detection because of its high sensitivity and low dark current.In this paper,the layout of p+/n-well/p-sub double junction photodiode is optimized based on 0.5 μm CMOS process,the effect of silicon and silicon dioxide interface on the dark current for the active region of the photodiode is reduced effectively.The test result of a tape-out chip shows that the dark current for the p+/n-well/p-sub double junction photodiode is reduced from 11 to 6.5 pA and the photoelectric sensitivity weakens slightly from 2.15 to 2.05 nA after optimization.So the light and dark current ratio increases by 60％.The results show that the optimal p+/n-well/p-sub double junction photodiode is more suitable for weak fluorescence signal detection.