MANAGING AND LEVERAGING VARIATIONS AND NOISE IN NANOMETER CMOS

Advanced CMOS technologies have enabled high density designs at the cost of complex fabrication process. Variation in oxide thickness and Random Dopant Fluctuation (RDF) lead to variation in transistor threshold voltage Vth. Current photo-lithography process used for printing decreasing critical dimensions result in variation in transistor channel length and width. A related challenge in nanometer CMOS is that of on-chip random noise. With decreasing threshold voltage and operating voltage; and increasing operating temperature, CMOS devices are more sensitive to random on-chip noise in advanced technologies. In this thesis, we explore novel circuit techniques to manage the impact of process variation in nanometer CMOS technologies. We also analyze the impact of on-chip noise on CMOS circuits and propose techniques to leverage or manage impact of noise based on the application. True Random Number Generator (TRNG) is an interesting cryptographic primitive that leverages on-chip noise to generate random bits; however, it is highly sensitive to process variation. We explore novel metastability circuits to alleviate the impact of variations and at the same time leverage on-chip noise sources like Random Thermal Noise and Random Telegraph Noise (RTN) to generate high quality random bits. We develop stochastic models for metastability based TRNG circuits to analyze the impact of variation and noise. The stochastic models are used to analyze and compare low power, energy efficient and lightweight post-processing techniques targeted to low power applications like System on Chip (SoC) and RFID. We also propose variation aware circuit calibration techniques to increase reliability. We extended this technique to a more generic application of designing Post-Si Tunable (PST) clock buffers to increase parametric yield in the presence of process variation. Apart from one time variation due to fabrication process, transistors undergo constant change in threshold voltage due to aging/wear-out effects and RTN. Process variation affects conventional sensors and introduces inaccuracies during measurement. We present a lightweight wear-out sensor that is tolerant to process variation and provides a fine grained wear-out sensing. A similar circuit is designed to sense fluctuation in transistor threshold voltage due to RTN. Although thermal noise and RTN are leveraged in applications like TRNG, they affect the stability of sensitive circuits like Static Random Access Memory (SRAM). We analyze the impact of on-chip noise on Bit Error Rate (BER) and post-Si test coverage of SRAM cells

NEGATIVE BIAS TEMPERATURE INSTABILITY STUDIES FOR ANALOG SOC CIRCUITS

Negative Bias Temperature Instability (NBTI) is one of the recent reliability issues in sub threshold CMOS circuits. NBTI effect on analog circuits, which require matched device pairs and mismatches, will cause circuit failure. This work is to assess the NBTI effect considering the voltage and the temperature variations. It also provides a working knowledge of NBTI awareness to the circuit design community for reliable design of the SOC analog circuit. There have been numerous studies to date on the NBTI effect to analog circuits. However, other researchers did not study the implication of NBTI stress on analog circuits utilizing bandgap reference circuit. The reliability performance of all matched pair circuits, particularly the bandgap reference, is at the mercy of aging differential. Reliability simulation is mandatory to obtain realistic risk evaluation for circuit design reliability qualification. It is applicable to all circuit aging problems covering both analog and digital. Failure rate varies as a function of voltage and temperature. It is shown that PMOS is the reliabilitysusceptible device and NBTI is the most vital failure mechanism for analog circuit in sub-micrometer CMOS technology. This study provides a complete reliability simulation analysis of the on-die Thermal Sensor and the Digital Analog Converter (DAC) circuits and analyzes the effect of NBTI using reliability simulation tool. In order to check out the robustness of the NBTI-induced SOC circuit design, a bum-in experiment was conducted on the DAC circuits. The NBTI degradation observed in the reliability simulation analysis has given a clue that under a severe stress condition, a massive voltage threshold mismatch of beyond the 2mV limit was recorded. Bum-in experimental result on DAC proves the reliability sensitivity of NBTI to the DAC circuitry

A Support Vector Regression based Machine Learning method for on-chip Aging Estimation

Semiconductor supply chain industry is spread worldwide to reduce cost and to meet the electronic systems high demand for ICs, and with the era of internet of things (IoT), the estimated numbers of electronic devices will rise over trillions. This drift in the semiconductor supply chain produces high volume of e-waste, which affects integrated circuits (ICs) security and reliability through counterfeiting, i.e., recycled and remarked ICs. Utilising recycled IC as a new one or a remarked IC to upgrade its level into critical infrastructure such as defence or medical electronics may cause systems failure, compromising human lives and financial loss. This paper harvests aging degradation induced by BTI and HCI, observing frequency and discharge time affected by changes in drain current and sub-threshold leakage current over time, respectively. Such task is undertaken by Cadence simulations, implementing a 51-stage ring oscillator (51-RO) using 22nm CMOS technology library and aging model provided by GlobalFoundries (GF). Machine learning (ML) algorithm of support vector regression (SVR) is adapted for this application, using a training process that involves operating temperature, discharge time, frequency, and aging time. The data sampling is performed over an emulated 12 years period with four representative temperatures of 20° C, 40° C, 60° C, and 80° C with additional testing data from temperatures of 25° C and 50° C. The results demonstrate a high accuracy on aging estimation by SVR, reported as a normal distribution with the mean (µ) equal to 0.01 years (3.6 days) and a standard deviation (σ) of ±0.1 years (±36 days)

Optimização dinâmica da tensão de alimentação e da frequência de operação em sistemas electrónicos digitais

À medida que a tecnologia de circuitos integrados CMOS é exposta à miniaturização, surgem diversos problemas no que diz respeito à fiabilidade e performance. Efeitos tais como o BTI (Bias Thermal Instability), TDDB (Time Dependent Dielectric Breakdown), HCI (Hot Carrier Injection), EM (Electromigration) degradam os parâmetros físicos dos transístores CMOS e por sua vez alteram as propriedades eléctricas dos mesmos ao longo do tempo. Esta deterioração é chamada de envelhecimento e estes efeitos são cumulativos e têm um grande impacto na performance do circuito, especialmente se ocorrerem outras variações paramétricas, como as variações de processo, temperatura e tensão de alimentação. Estas variações são conhecidas por variações PVTA (variações no Processo de Fabricação do circuito integrado [P], na Tensão de Alimentação [V], na Temperatura [T] e variações provocadas pelo Envelhecimento dos circuitos [A]) e podem desencadear erros de sincronismo durante a vida do produto (circuito integrado digital). O trabalho apresentado nesta dissertação tem por objectivo primordial o desenvolvimento de um sistema que optimize a operação ao longo da vida de circuitos integrados digitais síncronos de forma dinâmica. Este sistema permite que os circuitos sejam optimizados de acordo com as suas necessidades: (i) Diminuir a dissipação de potência, por reduzir a tensão de alimentação para o valor mais baixo que garante a operação sem erros; ou (ii) Aumentar o desempenho/performance, por aumentar a frequência de operação até ao limite máximo no qual não ocorrem erros. A optimização dinâmica da operação ao longo da vida de circuitos integrados digitais síncronos é alcançada através de um controlador, um bloco de sensores globais e por vários sensores locais localizados em determinados flip-flops do circuito. A nova solução tem como objectivo utilizar os dois tipos de sensores atrás mencionados, globais e locais, para possibilitar a previsão de erros de performance de uma forma mais eficaz, que possibilite a activação de mecanismos que impeçam a ocorrência de erros durante o tempo de vida útil de um circuito, e dessa forma permitindo optimizar constantemente o seu funcionamento. Assim é exequível desenvolver circuitos que operem no limite das suas capacidades temporais, sem falhas, e com a utilização de margens de erro pequenas para admitir as variações de performance provocadas por variações no processo de fabrico, na tensão de alimentação, na temperatura ou o envelhecimento. Foi também desenvolvido um sistema de controlo que permite, depois da detecção de um potencial erro, desencadear um processo para diminuir a frequência do sinal de relógio do sistema, ou aumentar a tensão de alimentação, evitando que o erro ocorra. Apesar de existirem outras técnicas de controlo dinâmico da operação de circuitos integrados tais como DVS (Dynamic Voltage Scaling), de DFS (Dynamic Frequency Scaling), ou ambas (DVFS – Dynamic Voltage and Frequency Scaling), estas técnicas ou são de muito complexa implementação, ou apresentam margens de segurança elevadas, levando a soluções em que a operação do circuito não está optimizada. A solução desenvolvida neste trabalho, em que se utilizam sensores preditivos locais e globais os quais são sensíveis ao envelhecimento a longo prazo ocorrido nos circuitos, constitui uma novidade no estado da técnica relativamente ao controlo de sistemas de DVS e/ou DFS. Outro aspecto importante é que neste trabalho desenvolveu-se um método de ajuste da tensão de alimentação ou da frequência, o qual é sensível ao envelhecimento a longo prazo dos circuitos, utilizando sensores locais e globais. O controlador permite a optimização da performance dos circuitos através do aumento da frequência de operação até ao limite máximo que ainda evita a ocorrência de erros e a optimização de consumo de energia através da redução da tensão de alimentação (VDD) para o valor mínimo que ainda previne a ocorrência de erros. Através de uma análise de previsão de envelhecimento, são identificados os caminhos críticos, bem como os caminhos que envelhecem mais rápido e que se tornarão críticos com o envelhecimento do circuito. Uma vez identificados os caminhos críticos, irão ser inserido os sensores locais através da substituição dos flip-flops que terminam os caminhos críticos identificados por novos flip-flops que incluem sensores de performance e de envelhecimento. É de referenciar que estes sensores são preditivos, ou seja, que sinalizam precocemente os erros de performance, antes de eles ocorrerem nos flip-flops que capturam os caminhos críticos. A arquitectura dos sensores propostos é tal que as variações PVTA que ocorrem sobre eles fazem aumentar a sua capacidade de prever o erro, ou seja, os sensores vão-se adaptando ao longo da sua vida útil para aumentarem a sua sensibilidade. Os sensores locais têm como função realizar a calibração dos sensores globais, bem como realizar a monitorização constante dos atrasos nos caminhos mais longos do circuito, sempre que estes são activados. A função dos sensores globais é a realização da monitorização periódica ou quando solicitado dos atrasos no circuito digital. Ambos os tipos de sensores, os sensores globais como os locais podem desencadear ajustes na frequência ou na tensão de alimentação. Os sensores globais são compostos por uma unidade de controlo do sensor global, que recebe ordens do controlador do sistema para iniciar a análise ao desempenho do circuito e gera os sinais de controlo para a operação de análise global do desempenho e por duas cadeias de portas (uma com portas NOR e outra com portas NAND), com tempos de propagação superiores aos caminhos críticos que se esperam vir a ter no circuito durante a sua vida útil. Ambos os caminhos irão, presumivelmente, envelhecer mais que os caminhos críticos do circuito quando sujeitos ao efeito BTI (que influencia fortemente a degradação do Vth dos transístores [NBTI/NORs e PBTI/NANDs]). Ao longo das duas cadeias, diversos sinais à saída de algumas portas NOR e NAND são ligados a células de sensores globais, criando diversos caminhos fictícios com diferentes tempos de propagação. As saídas dos sensores das duas cadeias formam duas saídas de dados do sensor global. A fim de se alcançar a optimização do desempenho do circuito, são realizados testes de calibração dos sensores, onde são estimulados alguns caminhos críticos no circuito (através de um teste determinístico) e, simultaneamente é realizada a análise do desempenho pela unidade de sensores globais. Este procedimento, permite definir o limite máximo (mínimo) para frequência (tensão de alimentação) sem que os sensores locais sejam sinalizados. Esta informação da frequência (tensão) é guardada num registo do controlador (registo V/F) e corresponde à frequência (tensão) normal de funcionamento. Este teste também permite determinar quais os caminhos fictícios nas duas cadeias que apresentam tempos de propagação semelhantes aos caminhos críticos do circuito. Esta informação também é guardada em dois registos no controlador do sistema (registos GSOsafe), que indicam o estado das saídas dos controladores globais para a operação optimizada do circuito. Durante a vida útil do circuito, o controlador do sistema de optimização procede ao ajuste automático da frequência (ou da tensão de alimentação) do circuito, caso o controlador dos sensores globais detecte uma alteração em relação à operação correcta em memória, alterando o conteúdo do registo que guarda a frequência (tensão) de trabalho. Se por ventura ocorrer a sinalização de um sensor local e não existir nenhuma sinalização para alteração do desempenho pelos sensores globais, quer dizer que o circuito pode ter envelhecido mais que os caminhos fictícios dos sensores globais, pelo que a frequência (tensão de alimentação) de funcionamento deve ser alterada, mas também deve existir uma actualização nos registos que guardam a saída correcta dos sensores globais. É de salientar que, se os caminhos fictícios envelhecem mais do que o circuito, as margens de segurança (time slack) existentes vão sendo aumentadas ao longo da vida do circuito, tratando-se de uma segurança positiva. Mas, se existir a possibilidade do envelhecimento ser maior nos caminhos do circuito, a existência dos sensores locais a monitorizar a todo o tempo o desempenho do circuito, garantem que o sistema pode aprender com as sinalizações e adaptar-se às novas condições de operação ao longo da vida útil do circuito. Enquanto a monitorização efectuada pelo bloco de sensores globais fornece uma avaliação grosseira do estado de funcionamento do circuito, a monitorização efectuada pelos sensores locais, quando activados, fornece uma avaliação fina sobre qual a performance do circuito para que não ocorram erros funcionais. As novidades apresentadas neste trabalho são no mecanismo de controlo que permite a optimização dinâmica da tensão ou da frequência, e na arquitectura e funcionamento do sensor global a inserir no circuito. No que diz respeito ao mecanismo de controlo do sistema de optimização dinâmica, as novidades são: (i) na utilização conjunta de sensores locais e globais para garantir níveis de optimização elevados, (ii) na utilização de sensores preditivos (globais e locais) que previnem os erros de ocorrerem e (iii) na utilização de sensores sensíveis ao envelhecimento do circuito ao longo da sua vida útil. Em relação ao sensor global para monitorização de variações PVTA a novidade consiste (iv), na apresentação de sensores para a degradação nos transístores PMOS e de sensores para a degradação nos transístores NMOS. Este método de optimização e as topologias apresentadas podem ser desenvolvidas e utilizadas com outros tipos de flip-flops, ou empregando outros tipos de sensores, ou outros caminhos fictícios nos sensores globais, sem prejuízo do método global de optimização que conjuga os dois tipos de sensores, globais e locais, para optimizar a tensão de alimentação e a frequência de operação. É proposta uma nova arquitectura para um flip-flop com correcção de erros de atraso (DFC-FF / AEPDFC-FF) com e sem previsão de erros adaptativa para realizar a correcção/monitorização e correcção on-line da perda de performance a longo prazo de sistemas digitais CMOS, independentemente da sua causa. O DFC-FF integra um FF do tipo TG-MSFF (Transmission Gate Master Slave Flip-Flop) e um sensor de correcção de erros (CES) dos quais são apresentados duas propostas. O AEPDFC-FF é composto por DFC-FF e um sensor de envelhecimento. A variabilidade tornou-se na principal causa de falha dos circuitos digitais quando a tecnologia evoluiu para as escalas nanométricas. As reduzidas dimensões físicas dos novos transístores e o aumento na complexidade dos circuitos integrados tornou os novos circuitos mais susceptíveis a variações no processo de fabrico, nas condições de operação e operacionais, tendo como consequência o fabrico de dispositivos mais frágeis, com maior probabilidade de falharem nos primeiros meses de vida, e com tempos de vida útil esperados inferiores aos das tecnologias anteriores. Face a outras propostas, uma das principais vantagens do DFC-FF é que a a perda de performance do próprio sensor melhora a sua capacidade de correcção de erros. Os efeitos do envelhecimento, do aumento de temperatura e da diminuição na tensão de alimentação (VTA), aumentam a janela de correcção, permitindo que o DFC-FF possa estar sempre ligado sem comprometer o seu funcionamento. O conceito, estudado e desenvolvido em tecnologia de 65nm, pode ser transportado posteriormente para nanotecnologias mais recentes, usando MOSFETs de menor dimensão, uma vez que a arquitectura do sensor é transversal a toda a tecnologia CMOS.Universidade do Algarve, Instituto Superior de Engenhari

Static random-access memory designs based on different FinFET at lower technology node (7nm)

Title from PDF of title page viewed January 15, 2020Thesis advisor: Masud H ChowdhuryVitaIncludes bibliographical references (page 50-57)Thesis (M.S.)--School of Computing and Engineering. University of Missouri--Kansas City, 2019The Static Random-Access Memory (SRAM) has a significant performance impact on current nanoelectronics systems. To improve SRAM efficiency, it is important to utilize emerging technologies to overcome short-channel effects (SCE) of conventional CMOS. FinFET devices are promising emerging devices that can be utilized to improve the performance of SRAM designs at lower technology nodes. In this thesis, I present detail analysis of SRAM cells using different types of FinFET devices at 7nm technology. From the analysis, it can be concluded that the performance of both 6T and 8T SRAM designs are improved. 6T SRAM achieves a 44.97% improvement in the read energy compared to 8T SRAM. However, 6T SRAM write energy degraded by 3.16% compared to 8T SRAM. Read stability and write ability of SRAM cells are determined using Static Noise Margin and N- curve methods. Moreover, Monte Carlo simulations are performed on the SRAM cells to evaluate process variations. Simulations were done in HSPICE using 7nm Asymmetrical Underlap FinFET technology. The quasiplanar FinFET structure gained considerable attention because of the ease of the fabrication process [1] – [4]. Scaling of technology have degraded the performance of CMOS designs because of the short channel effects (SCEs) [5], [6]. Therefore, there has been upsurge in demand for FinFET devices for emerging market segments including artificial intelligence and cloud computing (AI) [8], [9], Internet of Things (IoT) [10] – [13] and biomedical [17] –[18] which have their own exclusive style of design. In recent years, many Underlapped FinFET devices were proposed to have better control of the SCEs in the sub-nanometer technologies [3], [4], [19] – [33]. Underlap on either side of the gate increases effective channel length as seen by the charge carriers. Consequently, the source-to-drain tunneling probability is improved. Moreover, edge direct tunneling leakage components can be reduced by controlling the electric field at the gate-drain junction . There is a limitation on the extent of underlap on drain or source sides because the ION is lower for larger underlap. Additionally, FinFET based designs have major width quantization issue. The width of a FinFET device increases only in quanta of silicon fin height (HFIN) [4]. The width quantization issue becomes critical for ratioed designs like SRAMs, where proper sizing of the transistors is essential for fault-free operation. FinFETs based on Design/Technology Co-Optimization (DTCO_F) approach can overcome these issues [38]. DTCO_F follows special design rules, which provides the specifications for the standard SRAM cells with special spacing rules and low leakages. The performances of 6T SRAM designs implemented by different FinFET devices are compared for different pull-up, pull down and pass gate transistor (PU: PD:PG) ratios to identify the best FinFET device for high speed and low power SRAM applications. Underlapped FinFETs (UF) and Design/Technology Co-Optimized FinFETs (DTCO_F) are used for the design and analysis. It is observed that with the PU: PD:PG ratios of 1:1:1 and 1:5:2 for the UF-SRAMs the read energy has degraded by 3.31% and 48.72% compared to the DTCO_F-SRAMs, respectively. However, the read energy with 2:5:2 ratio has improved by 32.71% in the UF-SRAM compared to the DTCO_F-SRAMs. The write energy with 1:1:1 configuration has improved by 642.27% in the UF-SRAM compared to the DTCO_F-SRAM. On the other hand, the write energy with 1:5:2 and 2:5:2 configurations have degraded by 86.26% and 96% in the UF-SRAMs compared to the DTCO_F-SRAMs. The stability and reliability of different SRAMs are also evaluated for 500mV supply. From the analysis, it can be concluded that Asymmetrical Underlapped FinFET is better for high-speed applications and DTCO FinFET for low power applications.Introduction -- Next generation high performance device: FinFET -- FinFET based SRAM bitcell designs -- Benchmarking of UF-SRAMs and DTCO-F-SRAMS -- Collaborative project -- Internship experience at INTEL and Marvell Semiconductor -- Conclusion and future wor

Robust Design of Variation-Sensitive Digital Circuits

The nano-age has already begun, where typical feature dimensions are smaller than 100nm. The operating frequency is expected to increase up to 12 GHz, and a single chip will contain over 12 billion transistors in 2020, as given by the International Technology Roadmap for Semiconductors (ITRS) initiative. ITRS also predicts that the scaling of CMOS devices and process technology, as it is known today, will become much more difficult as the industry advances towards the 16nm technology node and further. This aggressive scaling of CMOS technology has pushed the devices to their physical limits. Design goals are governed by several factors other than power, performance and area such as process variations, radiation induced soft errors, and aging degradation mechanisms. These new design challenges have a strong impact on the parametric yield of nanometer digital circuits and also result in functional yield losses in variation-sensitive digital circuits such as Static Random Access Memory (SRAM) and flip-flops. Moreover, sub-threshold SRAM and flip-flops circuits, which are aggravated by the strong demand for lower power consumption, show larger sensitivity to these challenges which reduces their robustness and yield. Accordingly, it is not surprising that the ITRS considers variability and reliability as the most challenging obstacles for nanometer digital circuits robust design. Soft errors are considered one of the main reliability and robustness concerns in SRAM arrays in sub-100nm technologies due to low operating voltage, small node capacitance, and high packing density. The SRAM arrays soft errors immunity is also affected by process variations. We develop statistical design-oriented soft errors immunity variations models for super-threshold and sub-threshold SRAM cells accounting for die-to-die variations and within-die variations. This work provides new design insights and highlights the important design knobs that can be used to reduce the SRAM cells soft errors immunity variations. The developed models are scalable, bias dependent, and only require the knowledge of easily measurable parameters. This makes them useful in early design exploration, circuit optimization as well as technology prediction. The derived models are verified using Monte Carlo SPICE simulations, referring to an industrial hardware-calibrated 65nm CMOS technology. The demand for higher performance leads to very deep pipelining which means that hundreds of thousands of flip-flops are required to control the data flow under strict timing constraints. A violation of the timing constraints at a flip-flop can result in latching incorrect data causing the overall system to malfunction. In addition, the flip-flops power dissipation represents a considerable fraction of the total power dissipation. Sub-threshold flip-flops are considered the most energy efficient solution for low power applications in which, performance is of secondary importance. Accordingly, statistical gate sizing is conducted to different flip-flops topologies for timing yield improvement of super-threshold flip-flops and power yield improvement of sub-threshold flip-flops. Following that, a comparative analysis between these flip-flops topologies considering the required overhead for yield improvement is performed. This comparative analysis provides useful recommendations that help flip-flops designers on selecting the best flip-flops topology that satisfies their system specifications while taking the process variations impact and robustness requirements into account. Adaptive Body Bias (ABB) allows the tuning of the transistor threshold voltage, Vt, by controlling the transistor body voltage. A forward body bias reduces Vt, increasing the device speed at the expense of increased leakage power. Alternatively, a reverse body bias increases Vt, reducing the leakage power but slowing the device. Therefore, the impact of process variations is mitigated by speeding up slow and less leaky devices or slowing down devices that are fast and highly leaky. Practically, the implementation of the ABB is desirable to bias each device in a design independently, to mitigate within-die variations. However, supplying so many separate voltages inside a die results in a large area overhead. On the other hand, using the same body bias for all devices on the same die limits its capability to compensate for within-die variations. Thus, the granularity level of the ABB scheme is a trade-off between the within-die variations compensation capability and the associated area overhead. This work introduces new ABB circuits that exhibit lower area overhead by a factor of 143X than that of previous ABB circuits. In addition, these ABB circuits are resolution free since no digital-to-analog converters or analog-to-digital converters are required on their implementations. These ABB circuits are adopted to high performance critical paths, emulating a real microprocessor architecture, for process variations compensation and also adopted to SRAM arrays, for Negative Bias Temperature Instability (NBTI) aging and process variations compensation. The effectiveness of the new ABB circuits is verified by post layout simulation results and test chip measurements using triple-well 65nm CMOS technology. The highly capacitive nodes of wide fan-in dynamic circuits and SRAM bitlines limit the performance of these circuits. In addition, process variations mitigation by statistical gate sizing increases this capacitance further and fails in achieving the target yield improvement. We propose new negative capacitance circuits that reduce the overall parasitic capacitance of these highly capacitive nodes. These negative capacitance circuits are adopted to wide fan-in dynamic circuits for timing yield improvement up to 99.87% and to SRAM arrays for read access yield improvement up to 100%. The area and power overheads of these new negative capacitance circuits are amortized over the large die area of the microprocessor and the SRAM array. The effectiveness of the new negative capacitance circuits is verified by post layout simulation results and test chip measurements using 65nm CMOS technology

Dynamic Partial Reconfiguration for Dependable Systems

Moore’s law has served as goal and motivation for consumer electronics manufacturers in the last decades. The results in terms of processing power increase in the consumer electronics devices have been mainly achieved due to cost reduction and technology shrinking. However, reducing physical geometries mainly affects the electronic devices’ dependability, making them more sensitive to soft-errors like Single Event Transient (SET) of Single Event Upset (SEU) and hard (permanent) faults, e.g. due to aging effects. Accordingly, safety critical systems often rely on the adoption of old technology nodes, even if they introduce longer design time w.r.t. consumer electronics. In fact, functional safety requirements are increasingly pushing industry in developing innovative methodologies to design high-dependable systems with the required diagnostic coverage. On the other hand commercial off-the-shelf (COTS) devices adoption began to be considered for safety-related systems due to real-time requirements, the need for the implementation of computationally hungry algorithms and lower design costs. In this field FPGA market share is constantly increased, thanks to their flexibility and low non-recurrent engineering costs, making them suitable for a set of safety critical applications with low production volumes. The works presented in this thesis tries to face new dependability issues in modern reconfigurable systems, exploiting their special features to take proper counteractions with low impacton performances, namely Dynamic Partial Reconfiguration

Integrated Electronics for Wireless Imaging Microsystems with CMUT Arrays

Integration of transducer arrays with interface electronics in the form of single-chip CMUT-on-CMOS has emerged into the field of medical ultrasound imaging and is transforming this field. It has already been used in several commercial products such as handheld full-body imagers and it is being implemented by commercial and academic groups for Intravascular Ultrasound and Intracardiac Echocardiography. However, large attenuation of ultrasonic waves transmitted through the skull has prevented ultrasound imaging of the brain. This research is a prime step toward implantable wireless microsystems that use ultrasound to image the brain by bypassing the skull. These microsystems offer autonomous scanning (beam steering and focusing) of the brain and transferring data out of the brain for further processing and image reconstruction. The objective of the presented research is to develop building blocks of an integrated electronics architecture for CMUT based wireless ultrasound imaging systems while providing a fundamental study on interfacing CMUT arrays with their associated integrated electronics in terms of electrical power transfer and acoustic reflection which would potentially lead to more efficient and high-performance systems. A fully wireless architecture for ultrasound imaging is demonstrated for the first time. An on-chip programmable transmit (TX) beamformer enables phased array focusing and steering of ultrasound waves in the transmit mode while its on-chip bandpass noise shaping digitizer followed by an ultra-wideband (UWB) uplink transmitter minimizes the effect of path loss on the transmitted image data out of the brain. A single-chip application-specific integrated circuit (ASIC) is de- signed to realize the wireless architecture and interface with array elements, each of which includes a transceiver (TRX) front-end with a high-voltage (HV) pulser, a high-voltage T/R switch, and a low-noise amplifier (LNA). Novel design techniques are implemented in the system to enhance the performance of its building blocks. Apart from imaging capability, the implantable wireless microsystems can include a pressure sensing readout to measure intracranial pressure. To do so, a power-efficient readout for pressure sensing is presented. It uses pseudo-pseudo differential readout topology to cut down the static power consumption of the sensor for further power savings in wireless microsystems. In addition, the effect of matching and electrical termination on CMUT array elements is explored leading to new interface structures to improve bandwidth and sensitivity of CMUT arrays in different operation regions. Comprehensive analysis, modeling, and simulation methodologies are presented for further investigation.Ph.D

Solid State Circuits Technologies

The evolution of solid-state circuit technology has a long history within a relatively short period of time. This technology has lead to the modern information society that connects us and tools, a large market, and many types of products and applications. The solid-state circuit technology continuously evolves via breakthroughs and improvements every year. This book is devoted to review and present novel approaches for some of the main issues involved in this exciting and vigorous technology. The book is composed of 22 chapters, written by authors coming from 30 different institutions located in 12 different countries throughout the Americas, Asia and Europe. Thus, reflecting the wide international contribution to the book. The broad range of subjects presented in the book offers a general overview of the main issues in modern solid-state circuit technology. Furthermore, the book offers an in depth analysis on specific subjects for specialists. We believe the book is of great scientific and educational value for many readers. I am profoundly indebted to the support provided by all of those involved in the work. First and foremost I would like to acknowledge and thank the authors who worked hard and generously agreed to share their results and knowledge. Second I would like to express my gratitude to the Intech team that invited me to edit the book and give me their full support and a fruitful experience while working together to combine this book