Monitor-Based In-Field Wearout Mitigation for CMOS RF Integrated Circuits

abstract: Performance failure due to aging is an increasing concern for RF circuits. While most aging studies are focused on the concept of mean-time-to-failure, for analog circuits, aging results in continuous degradation in performance before it causes catastrophic failures. In this regard, the lifetime of RF/analog circuits, which is defined as the point where at least one specification fails, is not just determined by aging at the device level, but also by the slack in the specifications, process variations, and the stress conditions on the devices. In this dissertation, firstly, a methodology for analyzing the performance degradation of RF circuits caused by aging mechanisms in MOSFET devices at design-time (pre-silicon) is presented. An algorithm to determine reliability hotspots in the circuit is proposed and design-time optimization methods to enhance the lifetime by making the most likely to fail circuit components more reliable is performed. RF circuits are used as test cases to demonstrate that the lifetime can be enhanced using the proposed design-time technique with low area and no performance impact. Secondly, in-field monitoring and recovering technique for the performance of aged RF circuits is discussed. The proposed in-field technique is based on two phases: During the design time, degradation profiles of the aged circuit are obtained through simulations. From these profiles, hotspot identification of aged RF circuits are conducted and the circuit variable that is easy to measure but highly correlated to the performance of the primary circuit is determined for a monitoring purpose. After deployment, an on-chip DC monitor is periodically activated and its results are used to monitor, and if necessary, recover the circuit performances degraded by aging mechanisms. It is also necessary to co-design the monitoring and recovery mechanism along with the primary circuit for minimal performance impact. A low noise amplifier (LNA) and LC-tank oscillators are fabricated for case studies to demonstrate that the lifetime can be enhanced using the proposed monitoring and recovery techniques in the field. Experimental results with fabricated LNA/oscillator chips show the performance degradation from the accelerated stress conditions and this loss can be recovered by the proposed mitigation scheme.Dissertation/ThesisDoctoral Dissertation Electrical Engineering 201

Design and Implementation of Software Defined Radios on a Homogeneous Multi-Processor Architecture

In the wireless communications domain, multi-mode and multi-standard platforms are becoming increasingly the central focus of system architects. In fact, mobile terminal users require more and more mobility and throughput, pushing towards a fully integrated radio system able to support different communication protocols running concurrently on the platform. A new concept of radio system was introduced to meet the users' expectations. Flexible radio platforms have became an indispensable requirement to meet the expectations of the users today and in the future. This thesis deals with issues related to the design of flexible radio platforms. In particular, the flexibility of the radio system is achieved through the concept of software defined radios (SDRs). The research work focuses on the utilization of homogeneous multi-processor (MP) architectures as a feasible way to efficiently implement SDR platforms. In fact, platforms based on MP architectures are able to deliver high performance together with a high degree of flexibility. Moreover, homogeneous MP platforms are able to reduce design and verification costs as well as provide a high scalability in terms of software and hardware. However, homogeneous MP architectures provide less computational efficiency when compared to heterogeneous solutions. This thesis can be divided into two parts: the first part is related to the implementation of a reference platform while the second part of the thesis introduces the design and implementation of flexible, high performance, power and energy efficient algorithms for wireless communications. The proposed reference platform, Ninesilica, is a homogeneous MP architecture composed of a 3x3 mesh of processing nodes (PNs), interconnected by a hierarchical Network-on-Chip (NoC). Each PN hosts as Processing Element (PE) a processor core. To improve the computational efficiency of the platform, different power and energy saving techniques have been investigated. In the design, implementation and mapping of the algorithms, the following constraints were considered: energy and power efficiency, high scalability of the platform, portability of the solutions across similar platforms, and parallelization efficiency. Ninesilica architecture together with the proposed algorithm implementations showed that homogeneous MP architectures are highly scalable platforms, both in terms of hardware and software. Furthermore, Ninesilica architecture demonstrated that homogeneous MPs are able to achieve high parallelization efficiency as well as high energy and power savings, meeting the requirements of SDRs as well as enabling cognitive radios. Ninesilica can be utilized as a stand-alone block or as an elementary building block to realize clustered many-core architectures. Moreover, the obtained results, in terms of parallelization efficiency as well as power and energy efficiency are independent of the type of PE utilized, ensuring the portability of the results to similar architectures based on a different type of processing element

Design and Implementation of Software Defined Radios on a Homogeneous Multi-Processor Architecture

In the wireless communications domain, multi-mode and multi-standard platforms are becoming increasingly the central focus of system architects. In fact, mobile terminal users require more and more mobility and throughput, pushing towards a fully integrated radio system able to support different communication protocols running concurrently on the platform. A new concept of radio system was introduced to meet the users' expectations. Flexible radio platforms have became an indispensable requirement to meet the expectations of the users today and in the future. This thesis deals with issues related to the design of flexible radio platforms. In particular, the flexibility of the radio system is achieved through the concept of software defined radios (SDRs). The research work focuses on the utilization of homogeneous multi-processor (MP) architectures as a feasible way to efficiently implement SDR platforms. In fact, platforms based on MP architectures are able to deliver high performance together with a high degree of flexibility. Moreover, homogeneous MP platforms are able to reduce design and verification costs as well as provide a high scalability in terms of software and hardware. However, homogeneous MP architectures provide less computational efficiency when compared to heterogeneous solutions. This thesis can be divided into two parts: the first part is related to the implementation of a reference platform while the second part of the thesis introduces the design and implementation of flexible, high performance, power and energy efficient algorithms for wireless communications. The proposed reference platform, Ninesilica, is a homogeneous MP architecture composed of a 3x3 mesh of processing nodes (PNs), interconnected by a hierarchical Network-on-Chip (NoC). Each PN hosts as Processing Element (PE) a processor core. To improve the computational efficiency of the platform, different power and energy saving techniques have been investigated. In the design, implementation and mapping of the algorithms, the following constraints were considered: energy and power efficiency, high scalability of the platform, portability of the solutions across similar platforms, and parallelization efficiency. Ninesilica architecture together with the proposed algorithm implementations showed that homogeneous MP architectures are highly scalable platforms, both in terms of hardware and software. Furthermore, Ninesilica architecture demonstrated that homogeneous MPs are able to achieve high parallelization efficiency as well as high energy and power savings, meeting the requirements of SDRs as well as enabling cognitive radios. Ninesilica can be utilized as a stand-alone block or as an elementary building block to realize clustered many-core architectures. Moreover, the obtained results, in terms of parallelization efficiency as well as power and energy efficiency are independent of the type of PE utilized, ensuring the portability of the results to similar architectures based on a different type of processing element

Bias Temperature Instability Modelling and Lifetime Prediction on Nano-scale MOSFETs

Bias Temperature Instability (BTI) is one of the most important reliability concerns for Metal Oxide Semiconductor Field Effect Transistors (MOSFET), the basic unit in integrated circuits. As the development MOSFET manufacturing technology, circuit designers need to consider device reliability during design optimization. An accurate BTI lifetime prediction methodology becomes a prerequisite. Typical BTI lifetime standard is ten years, accelerated BTI tests under high stress voltages are mandatory. BTI modelling is needed to project BTI lifetime from high voltages (accelerated condition) to operating voltage. The existing two mainstream BTI models: 1). The Reaction-Diffusion (R-D) framework and 2). The Two-Stage model cannot provide accurate lifetime prediction. Quite a few fitting parameters and unjustifiable empirical equations are needed in the R-D framework to predict the lifetime, questioning its predicting capability. The Two-stage model cannot project device lifetime from high voltages to operating voltage. Moreover, the scaling down of MOSFET feature size brings new challenges to nano-scale device lifetime prediction: 1). Nano-scale devices’ current is fluctuating due to the impact of a single charge is increasing as MOSFET scaling down, repetitive tests need to be done to achieve meaningful averaged results; 2). Nano-scale devices have significant Device-to-Device variability, making the lifetime a distribution instead of a single value. In this work a comprehensive As-grown Generation (A-G) framework based on the A-G model and defect centric theory is proposed and successfully predicts the Time Dependent Variability and lifetime on nano-scale devices. The predicting capability is validated by the good agreement between the test data and predicted values. It is speculated that the good predicting capability is due to the correct understanding of different types of defects. In the A-G framework, Time Dependent Variability is experimentally separated into Within-Device Fluctuation and the averaged degradation. Within-Device Fluctuation can be directly measured and the averaged degradation can be modelled using the A-G model. The averaged degradation in the A-G model contains: Generated Defects, As-grown Traps and Energy Alternating Defects. These defects have different kinetics against stress time thus need separate modelling. Various patterns such as Stress-Discharge-Recharge, multi-Discharging-based Multiple Pulses are designed to experimentally separate these defects based on their different charging/discharging properties. Fast-Voltage Step Stress technique is developed to reduce the testing time by 90% for the A-G framework parameter extraction, making the framework practical for potential use in industry