Characterization of large-scale non-uniformities in a 20k TDC/SPAD array integrated in a 130nm CMOS process

With the emergence of large arrays of high-functionality pixels, it has become critical to characterize the performance non-uniformity of such arrays. In this paper we characterize a 160×128 array of complex pixels, each with a single-photon avalanche diode (SPAD) and a time-to-digital converter (TDC). A study of the array's non-uniformities in terms of the timing resolution, jitter, and photon responsivity is conducted for the pixels at various illumination levels, temperatures, and other operating conditions. In the study we found that, in photon-starved operation, the TDCs exhibit a median resolution of 55ps and a standard deviation of 2 ps. The pixels show a median timing jitter of 140ps. Moreover, we measured negligible variations in photon responsivity while changing the number of active pixels. These findings suggest that the image sensor can be used in highly reliable, large-scale, time-correlated measurements of single photons for biological, molecular, and medical applications. The chip is especially valuable for time-resolved imaging, single-photon counting, and correlation-spectroscopy under many realistic operating conditions.