A 192×128 Time Correlated Single Photon Counting Imager in 40nm CMOS Technology

A 192 × 128 pixel single photon avalanche diode (SPAD) time-resolved single photon counting (TCPSC) image sensor is implemented in STMicroelectronics 40nm CMOS technology. The 13 % fill-factor, 18.4×9.2 μm pixel contains a 33 ps resolution, 135 ns full-scale, 12-bit time to digital converter (TDC) with 0.9 LSB differential and 5.64 LSB integral nonlinearity (DNL/INL). The sensor achieves a mean 219 ps full-width half maximum (FWHM) impulse response function (IRF) and is operable at up to 18.6 kfps. Cylindrical microlenses with a concentration factor of 3.25 increase the fill-factor to 42 %. The median dark count rate (DCR) is 25 Hz at 1.5 V excess bias. Fluorescence lifetime imaging (FLIM) results are presented.