Pixel structure effects on crosstalk in backwall illuminated CMOS compatible photodiode arrays

CMOS imaging arrays in back-illuminated mode provide a means to realize photodiode arrays for high resolution imaging systems, provided crosstalk effects can be reduced to the level of those observed in front-illuminated arrays. In this study, we have simulated the crosstalk in back-illuminated and front-illuminated arrays as a function of different structural configurations, including the presence of biased guard electrodes in single junction photodiodes, or the development of double junction photodiodes. The results obtained show that significant crosstalk suppression can be achieved in back-illuminated arrays for these structures. The physical mechanisms responsible for electrical crosstalk, and its subsequent suppression, are explained using an absorption volume proportion concept.