质子辐照下CMOS图像传感器随机电报信号机理研究

Random Telegraph Signal Mechanism on CMOS Image Sensors After Proton Irradiation

针对星用CMOS图像传感器面临的质子辐照导致像素性能退化问题,基于中国原子能科学研究院100 MeV质子回旋加速器试验装置,开展质子辐照导致CMOS图像传感器随机电报信号研究。试验结果表明,CMOS图像传感器积累的位移损伤剂量为240 TeV·g^(-1)时,质子辐照产生的随机电报信号占比为21.4%。随机电报信号可在2~8个固定的暗电流台阶之间随机波动,而且其行为受积分时间调控。分析认为,质子辐照CMOS图像传感器产生的随机电报信号来自于光电二极管,与像素内晶体管无关。质子辐照诱发的复杂位移缺陷是导致光电二极管随机电报信号的原因,复杂位移缺陷在室温条件下可以在不同结构之间随机转换,引起暗电流随机波动。低温工作条件可以有效抑制质子辐照导致的随机电报信号。

This paper focuses on the pixel performance degradation problem faced by CMOS image sensors in space applications.Taking the domestic back-illuminated 0.18μm CMOS image sensor as the research object,based on the 100 MeV proton cyclotron facility at China Institute of Atomic Energy,random telegraph signal caused by proton irradiation on CMOS image sensors is studied.The experimental results show that when the deposited displacement damage dose on CMOS image sensors reaches 240 TeV·g-1,the percentage of proton irradiation-induced random telegraph signal is 21.4%.Random telegraph signal fluctuates randomly from 2 to 8 discrete dark current values and its behavior is influenced by integration time.It is concluded that proton irradiation-induced random telegraph signal originates from the photodiode on CMOS image sensor and is independent of the in-pixel transistor.Random telegraph signals in the photodiodes are attributed to complex displacement defects induced by proton irradiation.This complex displacement defect can randomly switch between different structures at room temperature,causing random fluctuations of dark current.Low operating temperature is able to effectively suppress the random telegraph signal of CMOS image sensors.