This work investigates the joint impact of device variability and transistor aging on the data integrity of SRAM cells implemented using 22 FDSOI. Our analysis is based on well-calibrated TCAD simulations that reproduce measurements from a commercial 22nm FDSOI technology node. The calibrations are done against measurement data for both I-V characteristics and variability data. We perform error analysis for SRAMs during hold and read operations under three different scenarios: (i) Fresh: time-zero variation (PV) alone caused by manufacturing variability, (ii) Aged: combined impact of PV and aging-induced increase in the transistor threshold voltage ($V_{TH}$) at the room temperature, (iii) Aged@85°C: combined impact of PV and transistor aging but at an elevated temperature of 85°C. Further, we explore how SRAM errors are exacerbated when the voltage is scaled down due to the reductions in noise margins. All error analyses were accurately performed in TCAD mixed-mode simulations for a complete 6-T SRAM cell. Finally, to investigate further how such errors impact the system level, we explore the corresponding induced accuracy drop in Deep Neural Networks (DNNs). Different quantized NNs are studied, and their sensitivity to errors in weights and activations is also explored. We demonstrate that short-term aging (i.e., when aging effects are combined with voltage scaling) results in a noticeable accuracy drop when ResNet20 and ResNet18 DNN models are examined on the CIFAR100 and Imagenet datasets, respectively.

Quantum confinement in 3-D device structure together with the newly employed materials like silicon-germanium (SiGe) in advanced technologies (e.g., FinFET, nanowire, nanosheets, etc.) makes transistors seriously suffer from localized self-heating effects in which generated heat within the transistor's channel is trapped inside. This is mainly due to the much lower channel and surrounding material thermal conductivity and hence lower ability for heat dissipation along with the firm isolation needed for better gate control. Self-heating effects strongly accelerate transistor aging and all the underlying defect generation mechanisms leading to serious reliability problems during the early life of chips. The key challenge in transistor self-heating when it comes to semiconductor testing is the profound difficulty in measuring self-heating directly as generated heat is trapped inside the transistor. Failing in capturing self-heating phenomenon during IC testing would later lead to chips malfunctions at run-time and hence early life failures because of reliability degradations and failure mechanisms will be unexpectedly accelerated akin to excessive internal temperatures. In this paper, we investigate the impact of self-heating effects on n-type and p-type FinFET transistors calibrated with Intel 14 nm measurement data using mature Technology CAD (TCAD) simulations. Then, the industry standard compact model for FinFET technologies (BSIM-CMG) is carefully calibrated to accurately model and reproduce all measurements. This enables circuit's designers, for the first time, to accurately investigate how emerging self-heating effects in transistors impacts the performance and power of large circuits. This opens new doors for developing novel Design-for-Testing methods that effectively reveal self-heating effects and increase the yield of chips.

With the rapid development of emerging technologies, especially the ferroelectric field-effect transistors (FeFETs), the density and energy efficiency of ternary content addressable memory (TCAM) have been increasingly improved. TCAM plays a major role in realizing In-Memory Computing and other brain-inspired computing concepts. Recently, the parallel search functionality of a FeFET based ultra-dense TCAM design is also enhanced with a Hamming distance-based approximate search scheme. However, in order to realize the highly-promising TCAM design, in which the approximate search function based on Hamming distance is implemented, it is inevitable to investigate the impact of temperature on the reliability of FeFET-based TCAM cells as well as all involved peripheral circuits. In this paper, the temperature impact on the FeFET at the device level and the approximate TCAM design at the circuit level is investigated for the first time. The demonstrated example of a FeFET-based TCAM array shows that the unique temperature dependency of a FeFET device can help mitigate the temperature impact on the FeFET TCAM array. Based on the observation, we showcase, evaluate, and discuss in detail one strategy to eliminate the temperature impact on the approximate TCAM design. Understanding and mitigating the deleterious impact of temperature on the reliability of FeFET-based TCAM circuits is essential to ensure reliable In-Memory Computing.

Self-heating is one of the biggest threats to reliability in current and advanced CMOS technologies like FinFET and Nanowire, respectively. Encapsulating the channel with the gate dielectric improved electrostatics, but also thermally insulates the channel resulting in elevated channel temperatures as the generated heat is trapped within the channel. Elevated channel temperatures lowers the performance, increases leakage power and degrades the reliability of circuits. Self-heating becomes worse in each new transistor structure (from planar transistor to FinFET to Nanowire) due to the ever-increasing thermal resistance of the transistor. This leads to elevated temperatures, which must be carefully considered while designing circuits. Otherwise, reliability cannot be ensured. This work presents a self-heating study to illustrate how self-heating matters in digital circuits. It also explores the impact of running workloads in SRAM arrays, such as register files in CPUs, and how self-heating effects in SRAM cells can be mitigated.

This is the first work that investigates the impact of Negative Bias Temperature Instability (NBTI) on the Self-Heating (SH) phenomenon in Silicon Nanowire Field-Effect Transistors (SiNW-FETs). We investigate the individual as well as joint impact of NBTI and SH on pSiNW-FETs and demonstrate that NBTI-induced traps mitigate SH effects due to reduced current densities. Our Technology CAD (TCAD)-based SiNW-FET device is calibrated against experimental data. It accounts for thermodynamic and hydrodynamic effects in 3-D nano structures for accurate modeling of carrier transport mechanisms. Our analysis focuses on how lattice temperature, thermal resistance and thermal capacitance of pSiNW-FETs are affected due to NBTI, demonstrating that accurate self-heating modeling necessitates considering the effects that NBTI aging has over time. Hence, NBTI and SH effects need to be jointly and not individually modeled. Our evaluation shows that an individual modeling of NBTI and SH effects leads to a noticeable overestimation of the overall induced delay increase in circuits due to the impact of NBTI traps on SH mitigation. Hence, it is necessary to model NBTI and SH effects jointly in order to estimate efficient (i.e. small, yet sufficient) timing guardbands that protect circuits against timing violations, which will occur at runtime due to delay increases induced by aging and self-heating.

The introduction of FinFET technology as an effective solution to continue technology scaling has pushed self-heating effects to the forefront of reliability challenges, especially at the 14nm technology node and below. Due to limited silicon volume for heat dissipation, elevated temperatures across the transistors channel can be generated during operation. This results in a considerable degradation of the key properties of transistors like decreased drain and increased leakage current. In addition, excessive temperatures considerably accelerate aging phenomena in transistors such as Bias Temperature Instability (BTI) and Hot Carrier Injection (HCI), which shorten the lifetime of circuits. In this work, we discuss how self-heating effects in FinFET transistors can prolong the delay of circuits leading to reliability problems. We evaluate self-heating in an entire SRAM block consisting of SRAM cells, pre-charging circuit, sense amplifiers and an output latch. When it comes to reliability and lifetime, we demonstrate how self-heating effects can result in larger aging-induced degradations which, in turn, enforce designers to include wider and wider safety margins to sustain reliability. Lastly, we provide an outlook of self-heating and reliability concerns in Negative Capacitance Field Effect Transistors (NCFET).