Random Telegraph Noise Degradation Caused by Hot Carrier Injection in a 0.8 µm-Pitch 8.3Mpixel Stacked CMOS Image Sensor.

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.

Minimal influence of estrous cycle on studies of female mouse behaviors.

Introduction: Sex bias has been an issue in many biomedical fields, especially in neuroscience. In rodent research, many scientists only focused on male animals due to the belief that female estrous cycle gives rise to unacceptable, high levels of variance in the experiments. However, even though female sexual behaviors are well known to be regulated by estrous cycle, which effects on other non-sexual behaviors were not always consistent in previous reports. Recent reviews analyzing published literature even suggested that there is no evidence for larger variation in female than male in several phenotypes. Methods: To further investigate the impact of estrous cycle on the variability of female behaviors, we conducted multiple behavioral assays, including the open field test, forced swimming test, and resident-intruder assay to assess anxiety-, depression-like behaviors, as well as social interaction respectively. We compared females in the estrus and diestrus stages across four different mouse strains: C57BL/6, BALB/c, C3H, and DBA/2. Results: Our results found no significant difference in most behavioral parameters between females in these two stages. On the other hand, the differences in behaviors among certain strains are relatively consistent in both stages, suggesting a very minimal effect of estrous cycle for detecting the behavioral difference. Last, we compared the behavioral variation between male and female and found very similar variations in most behaviors between the two sexes. Discussion: While our study successfully identified behavioral differences among strains and between the sexes, we did not find solid evidence to support the notion that female behaviors are influenced by the estrous cycle. Additionally, we observed similar levels of behavioral variability between males and females. Female mice, therefore, have no reason to be excluded in future behavioral research.

Lack of social touch alters anxiety-like and social behaviors in male mice.

The importance of social interactions has been reported in a variety of animal species. In human and rodent models, social isolation is known to alter social behaviors and change anxiety or depression levels. During the coronavirus pandemic, although people could communicate with each other through other sensory cues, social touch was mostly prohibited under different levels of physical distancing policies. These social restrictions inspired us to explore the necessity of physical contact, which has rarely been investigated in previous studies on mouse social interactions. We first conducted a long-term observation to show that pair-housed mice in a standard laboratory cage spent nearly half the day in direct physical contact with each other. Furthermore, we designed a split-housing condition to demonstrate that even with free access to visual, auditory, and olfactory social signals, the lack of social touch significantly increased anxiety-like behaviors and changed social behaviors. There were correspondingly higher levels of the pro-inflammatory cytokine interleukin-6 in the hippocampus in mice with no access to physical contact. Our study demonstrated the necessity of social touch for the maintenance of mental health in mice and could have important implications for human social interactions.

Random Telegraph Noises from the Source Follower, the Photodiode Dark Current, and the Gate-Induced Sense Node Leakage in CMOS Image Sensors.

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.

Statistical Analysis of the Random Telegraph Noise in a 1.1 µm Pixel, 8.3 MP CMOS Image Sensor Using On-Chip Time Constant Extraction Method.

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.