In this work, the degradation of the random telegraph noise (RTN) and the threshold voltage (Vt) shift of an 8.3Mpixel stacked CMOS image sensor (CIS) under hot carrier injection (HCI) stress are ...investigated. We report for the first time the significant statistical differences between these two device aging phenomena. The Vt shift is relatively uniform among all the devices and gradually evolves over time. By contrast, the RTN degradation is evidently abrupt and random in nature and only happens to a small percentage of devices. The generation of new RTN traps by HCI during times of stress is demonstrated both statistically and on the individual device level. An improved method is developed to identify RTN devices with degenerate amplitude histograms.
A study of the random telegraph noise (RTN) of a 1.1 μm pitch, 8.3 Mpixel CMOS image sensor (CIS) fabricated in a 45 nm backside-illumination (BSI) technology is presented in this paper. A noise ...decomposition scheme is used to pinpoint the noise source. The long tail of the random noise (RN) distribution is directly linked to the RTN from the pixel source follower (SF). The full 8.3 Mpixels are classified into four categories according to the observed RTN histogram peaks. A theoretical formula describing the RTN as a function of the time difference between the two phases of the correlated double sampling (CDS) is derived and validated by measured data. An on-chip time constant extraction method is developed and applied to the RTN analysis. The effects of readout circuit bandwidth on the settling ratios of the RTN histograms are investigated and successfully accounted for in a simulation using a RTN behavior model.
This paper presents a sub-electron temporal readout noise, 8.3 Mpixel and 1.1-μ 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 mm 2 . 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.
In this paper we present a systematic approach to sort out different types of random telegraph noises (RTN) in CMOS image sensors (CIS) by examining their dependencies on the transfer gate ...off-voltage, the reset gate off-voltage, the photodiode integration time, and the sense node charge retention time. Besides the well-known source follower RTN, we have identified the RTN caused by varying photodiode dark current, transfer-gate and reset-gate induced sense node leakage. These four types of RTN and the dark signal shot noises dominate the noise distribution tails of CIS and non-CIS chips under test, either with or without X-ray irradiation. The effect of correlated multiple sampling (CMS) on noise reduction is studied and a theoretical model is developed to account for the measurement results.
The effects of X-ray irradiation on the random noises, especially the random telegraph noises (RTN), of a 45-nm on 65-nm stacked CMOS image sensor with 8.3M 1.1 μm pixels are investigated. It is ...found that before X-ray irradiation the dominant type of RTN among the noisiest pixels is the source follower (SF) MOSFET channel RTN. In contrast, after X-ray irradiation up to a total ionizing dose of 1 Mrad(SiO 2 ), the RTN becomes dominated by the variable transfer-gate-induced sense node (SN) leakage. These two different types of RTN can be distinguished by their dependence on the transfer gate (TG) OFF voltage and the time between the correlated double sampling (CDS). The magnitude of the RTN from the variable SN leakage is proportional to the CDS time and can be suppressed effectively by increasing the TG OFF voltage, whereas the SF RTN is independent of the CDS time or the TG OFF voltage.
A new method for on-chip random telegraph noise (RTN) characteristic time constant extraction using the double sampling circuit in an 8.3 Mpixel CMOS image sensor is described. The dependence of the ...measured RTN on the time difference between the double sampling and the key equation used for time constant extraction are derived from the continuous time RTN model and the discrete event RTN model. Both approaches lead to the same result and describe the data reasonably well. From the detailed study of the noisiest 1000 pixels, we find that about 75% to 85% of them show the signature of a single-trap RTN behavior with three distinct signal levels, and about 96% of the characteristic time constants fall between 1 μs and 500 μs with the median around 10 μs at room temperature.
Random Telegraph Noise (RTN) is a type of electronic noise that occurs in semiconductors and ultra-thin gate oxide films. RTN data acquisition and analysis require multiple measurements of millions ...of devices which is time consuming. This paper presents the design of a real-time RTN analysis system which achieved 17x speed boost with same accuracy by real-time processing noise data through DDR3 memory access. The designed system reduces the per wafer RTN analysis time from 5.5 hours to 0.33 hour.
The pinned photodiode capacitance extraction method proposed by Goiffon et al. is discussed, and two additional new methods are presented and analyzed; one based on the full well dependence on photon ...flux and the other based on the full well dependence on transfer-gate off-voltage.
Slow-motion video is a desirable feature for state-of-art smartphones. The effect is achieved by capturing a video at a higher frame rate and playing it back at a lower frame rate. While the ...still-image resolution of smartphone cameras ranges from 8MP to 25MP, standard videos are limited to 3 formats: 3840×2160 (4K2K, 2160p), 1920×1080 (Full High Definition, FHD, 1080p), and 1280×720 (High Definition, HD, 720p). CMOS image sensors using various column-parallel aDc architectures have been reported to reach high frame rates 1-5. The single-slope (SS) ADC is an attractive choice for a balanced performance among high speed, low noise, small area, and low power consumption. However, in conventional SS ADC design, each ADC is hardwired to a column signal line. ADCs for skipped columns are left idle during the subsampling operation, and the potential to reach higher frame rate is not optimized. In this paper, we develop an approach in which all the column ADCs are fully utilized in both of the 2-to-1 and 3-to-1 subsampling modes, such that the maximum of 4x faster FHD and 9x faster HD videos are demonstrated with reference to the 1-to-1 non-subsampled 4K2K video.
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