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It is difficult to measure the random telegraph noises (RTN) of MOSFET subthreshold currents at the sub-pA level directly and accurately. In this work, we used a charge integration method similar to the operation of the CMOS image sensors (CIS) to characterize the RTN of subthreshold currents approximately from 1 fA to 1 nA, using a test chip of 1M cell array in a 40 nm process. We found that each RTN trap was active only within a specific window of gate voltages. The trap became less active or inactive outside the corresponding window of operations. We showed that the sets of RTN-active devices under different gate voltages were different. Furthermore, the choice of sampling frequency in measuring RTN and the number of sampled data points determined the observable range of RTN emission and capture time constants. For the data measured by sampling periods of 3.82 s, 299 ms, and 372 $\mu {\mathrm{ s}}$ , different sets of RTN traps were observed with different spans of time constants. The combined time constants range was about 7 orders of magnitude. For single-trap RTN, we found and verified a relation between the probability of trap occupancy (PTO) and the ratio of root-mean-square random noise (RN) versus the RTN amplitude.

This paper presents a sub-electron temporal readout noise, 8.3 Mpixel and 1.1- $\mu \text{m}$ pixel pitch 3-D-stacked CMOS image sensor (CIS). A conditional correlated multiple sampling (CMS) technique is introduced to selectively reduce the dark pixel noise by using a full-range ramp and a small-range ramp. In this way, a sub-electron temporal readout noise CIS is achieved without degrading the frame rate dramatically, compared to the conventional CMS method. A column-parallel single slope ADC with dark pixel detection function is proposed as well. A dynamic-dark-signal-region detection technique is used to mitigate differential nonlinearity (DNL) errors due to ramp slope mismatch. The implemented prototype in 45-nm CIS/65-nm CMOS occupies an area of 35.89 mm2. This paper achieves a 0.66erms− with 5-time sampling at a frame rate of 7.2 frames/s, which corresponds to a sample-rate frequency of 36.1 kHz for the column ADC. The DNL (11 b) is improved from +0.98 LSB/−0.94 LSB to +0.29 LSB/−0.39 LSB by using dynamic dark-signal region technique. The figure of merit of this paper is 2.02 nVrms/Hz.