Process variability in FinFET standard cells with different transistor sizing techniques

In this paper. The effect of intradie process variations oy the delay of tapered buffers designed in static CMOS logic style is analyzed in depth. An analytical delay model accounting for the dependency of variations on transistor sizing, load and input capacitance requirement is derived for the single stage. Then, this model is extended to the case of N-stage tapered buffers. The closed-form delay expressions includin. The contribution of intradie variations permit to gain an insight int. The impact of process variations oy the performance of tapered buffers. Monte Carlo simulations on a 90-nm technology including layout parasitica are performed to validat. The analysis. Results are shown to agree well wit. The expressions derived, thereby confirmin. The validity oy the underlying assumptions, as well at the suitability oy the proposed models for design purposes. © 2009 IEEE.

A radiation hardening technique for combinational logic circuits is described. The key idea is to exploit the asymmetric logical masking probabilities of gates, hardening gates that have the lowest logical masking probability to achieve cost-effective tradeoffs between overhead and soft error failure rate reduction. The technique, which decouples the physical from the logical aspects of soft error susceptibility of a gate, uses a gate (transistor) sizing technique that is both efficient and accurate (in comparison to SPICE). A full set of experimental results demonstrate the cost-effective tradeoffs that can be achieved.

Advances in the fabrication technology have been a major driving force in the unprecedented increase in computing capabilities over the last several decades. Despite huge reductions in the switching energy of the transistors, two major issues have emerged with decreasing fabrication technology scales. They are: 1) increased impact of process, voltage, and temperature (PVT) variation on transistor performance, and 2) increased susceptibility of transistors to soft errors induced by high energy particles. In presence of PVT variation, as transistor sizes continue to decrease, the design margins used to guarantee correct operation in the presence of worst-case scenarios have been increasing. Systems run at a clock frequency, which is determined by accounting the worst-case timing paths, operating conditions, and process variations. Timing speculation based reliable and aggressive clocking advocates going beyond worst-case limits to achieve best performance while not avoiding, but detecting and correcting a modest number of timing errors. Such design methodology exploit the fact that timing critical paths are rarely exercised in a design, and typical execution happens much faster than the timing requirements dictated by worst-case scenarios. Better-than-worst-case design methodology is advocated by several recent research pursuits, which propose to exploit in-built fault tolerance mechanisms to enhance computer system performance. Recent works have also shown that the performance lose due to over provisioning base on worst-case design margins is upward of 20% in terms operating frequency and upward of 50% in terms of power efficiency. The threat of soft error induced system failure in computing systems has become more prominent as we adopt ultra-deep submicron process technologies. With respect to soft error susceptibility, decreasing transistor geometries lower the energy threshold needed by high-energy particles to induce errors. As this trend continues, the need for fault tolerance mechanisms to counteract this effect has moved from a nice to have, to be a requirement in current and future systems. In this dissertation,

Statistical yield improvement under process variations of multi-valued memristor-based memories

As technology scales to 45 nm and below, process variations will present significant impact on path delay. This trend makes the deviation between simulated path delay and actual path delay in a manufactured chip more significant. In this paper, we propose a new on-chip path delay measurement structure called path-based ring oscillator (Path-RO). The proposed method creates an oscillator from a targeted path for which it is used to measure path delay on-chip under the impact of process variations. To alleviate accuracy degradation caused by the architecture itself, a high-accuracy calibration process is presented. Through experimental results on Path-ROs inserted in ITCpsila99 b19 benchmark, we obtain path delay distribution under different process variations. The accuracy and efficiency of path delay measurement using Path-RO are also verified by comparing the results obtained from post-layout Hspice simulations.

High Throughput Asynchronous NoC Design under High Process Variation

STT-RAM (Spin Transfer Torque Random Access Memory) has been extensively researched as a potential replacement of SRAM (Static RAM) as on-chip caches. Prior work has shown that STT-RAM caches can improve performance and reduce power consumption because of its advantages of high density, fast read speed, low standby power, etc. However, under the impact of process variations, using worst-case design can induce significant performance and power overhead in STT-RAM caches. In order to overcome the problem of process variations, we propose to apply the variable-latency access method to STT-RAM caches by introducing a variation-aware LRU (Least Recently Used) policy. Moreover, we show that simply applying traditional variable-latency access method is inefficient due to the read/write asymmetry. First, we demonstrate that a write-oriented data migration is preferred. Second, a block remapping is necessary to prevent some cache sets from being significantly affected by process variations. After using our techniques, the experimental results show that the performance can be improved by 13.8% and power consumption can be reduced by 14.1% compared to a prior approach [3].

Leakage power is becoming a dominant contributor to the total power consumption and dual-V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sub> assignment is an efficient technique to decrease leakage power, for which effective design methods have been proposed. However, due to the exponential relation of subthreshold current with process parameters, such as, the effective gate length, oxide thickness and doping concentration, process variations can severely affect both power and timing yields of the designs obtained by those methods. In this paper, we propose a mixed integer linear programming method for dual-V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sub> design that minimizes the leakage power and circuit delay in a statistical sense such that the impact of process variation on the respective yields is minimized. The experimental results show that 30% more leakage power reduction can be achieved by using statistical approach when compared with the deterministic approach

Schmitt Trigger 12T1M Non-volatile SRAM cell with improved process variation tolerance

Due to aggressive technology scaling in nanometer regime, the impact of process variations on IC design has become a challenge. Process variations are usually classified into two types: inter-die and intra-die variations. The focus of this paper is on intra-die variations, which were ignored in the past, and are now significantly impacting the performance of modern circuits. A novel statistical gate-sizing metric is proposed to enhance the performance of digital integrated circuits in the presence of local intra-die process variations. The metric selects the most beneficial gates to be resized for improving circuit performance at a lower area cost. The proposed gate-sizing metric provides a means to increase yield leading to better chip revenue.

Over the last fifty years Complementary Metal Oxide Semiconductor (CMOS) technology has been scaled down, making the design of high-performance applications possible. However, there is a growing concern that device scaling will become infeasible below a certain feature size. In parallel, emerging applications present high demands regarding storage and computing capability, combined with challenging constraints. In this scenario, memristive devices have become promising candidates to replace or complement CMOS technology due to their CMOS manufacturing process compatibility, zero standby power consumption as well as high scalability and density. Despite these advantages, the implementation of high-density memories based on memristive devices poses some challenges related manufacturing process variation and consequently, to their reliability during lifetime. This paper investigates the impact of manufacturing process variation on Resistive Random Access Memories (RRAMs). In more detail, an evaluation of the RRAM&#x0027;s functionality when considering different levels of manufacturing process variation is performed. The obtained results show that different parameters can degrade the functionality of the RRAM cell as well as that there is a relation between the performed operating sequence and the tolerated percentage of variability. Finally, it is important to mention that understanding how process variation impacts the functionality of RRAM cells is considered essential to guarantee their reliability during lifetime, also allowing to optimize manufacturing processes.

Gate oxide breakdown is a major cause of reliability failures in future nanometer-scale CMOS designs. This paper develops an analysis technique that can predict the probability of a functional failure in a large digital circuit due to this phenomenon. Novel features of the method include its ability to account for the inherent resilience in a circuit to a breakdown event, while simultaneously considering the impact of process variations. Based on standard process variation models, at a specified time instant, this procedure determines the circuit failure probability as a lognormal distribution. Experimental results demonstrate this approach is accurate compared with Monte Carlo simulation, and gives 4.7-5.9× better lifetime prediction over existing methods that are based on pessimistic area-scaling models.

In this paper, we propose an accurate and computationally efficient Gradient Boosting approach for the estimation of statistical variations aware leakage power and propagation delay in the CMOS/FinFET standard digital cells. The proposed model estimates the leakage power and propagation delay w.r.t variations in process, temperature (−55°C to 125°C) and supply voltage(±10% variations). The distinguishing feature of the proposed approach is its compatibility with both CMOS and FinFET technologies. Moreover, the performance of the proposed model is consistent with various technology nodes. Exhaustive tests report an average error of <1% in 16nm CMOS and FinFET standard digital cells w.r.t analog HSPICE simulations with several orders increase in computational speed. Further, the complex cell estimation can be carried out through precharacterized standard cells abstaining longer simulations.

In this paper, the layout density of three-terminal FinFET logic circuits is extensively analyzed. As opposite to previous works, which are focused either on single devices or simplistic circuits, this analysis explicitly includes the geometric constraints that are imposed by the standard cell approach. The impact of the fin technology is analyzed by comparing the lithography- and spacer-defined approaches, as well as evaluating the dependence of layout density on the fin height. Results show that FinFET standard cells have a layout density that is better than bulk cells even for moderately tall fins. The fin height is also shown to be a powerful knob to improve the layout density in FinFET cells. Analysis also shows that the usually claimed 2X density improvement of the spacer-defined technology compared to the lithography-defined is dramatically reduced in real standard cells, and can be negligible for tall fins. All results are justified through considerations at the physical level of abstraction. Various versions of a 32-nm 44-gate library are laid out to carry out the analysis.

We present an in-depth analysis of the nanowire and nanotube device performance under process variability. While every process parameter variation drastically affects the conventional MOSFET performance, we found that nanowire/nanotube FETs are significantly (> 4X) less sensitive to many process parameter variations.