Seminars Spring 2004

Abstract:

Measures of the rate of progress in microelectronics, known as Moore's law, have been very useful in prediction and future planning. This progress can perhaps best be understood in terms of the concept of scaling which was introduced by the speaker and coworkers in the early 1970's. We have come to expect reduction of the transistor and wiring dimensions at a regular pace, along with the critical gate oxide thickness which makes transistor scaling work. Over the last thirty-five years these dimensions have been reduced by a factor of about 80-100, leading to the present situation where we are encountering basic barriers to further scaling of dimensions. This presentation addresses whether and when this progress will slow or cease and the microelectronics industry will mature. Also, what will microelectronics be like in maturity and can it support all our needs for computing?

Abstract:

Soft errors in scaled technologies beyond 90nm are posing a major challenge for design of memories and logic in future high performance microprocessors. Historically, we had to consider power-performance-area tradeoff. There is a need to consider soft error rate (SER) as another design parameter. We describe both cosmic ray and alpha-particle induced soft errors, an experiment to characterize bit-level SER and a method to compute SER of large circuit blocks. We also present scaling trends and SER-tolerant architecture/circuit techniques.

Abstract:

As processors move towards multi-core designs, on-chip interconnection networks are becoming the critical communication backbone that facilitates collaborative processing among the cores. In this talk, I'll address the power and thermal impact of these chip-scale networks, starting with several case studies highlighting the power and thermal contribution of these networks, along with details of our architectural network power and thermal models. Next, two distributed, collaborative approaches towards realizing power and thermal-aware networks will be discussed -- First, a design methodology we propose for power-aware networks with links turned dynamically on/off in response to actual utilization; Second, a run-time thermal management protocol towards regulating network temperature. Finally, I'll touch on how we see the distributed, collaborative approaches towards power and thermal-aware networks forming the foundation for entire power and thermal-aware multi-core processor chips.

Abstract:

The RF performance of scaled CMOS continues to improve. For some of us, the sources of noise in a FET appear complicated and mysterious. Worse, our intuitiion and insight into what we can do to improve noise figure (NF) in a low noise amplifier (LNA) may be lacking. This presentation will review basic noise models in MOSFETs, and interpret them as they apply to a narrow-band LNA. Additionaly, an approach to optimizing an LNA for low noise figure will be presented. The important difference between optimizing a transistor for NFmin and optimizing an LNA for minimum noise figure will be stressed.

Abstract:

Fundamental limits have lead to the pessimistic predictions of the imminent end of technological progress in semiconductor industry. However, the push to scale conventional MOSFET has continued to show remarkable progress. Continued scaling and demand for performance are pushing for lower supply voltage and Vt, shorter channel length, and thinner gate oxide. In addition, new device structures such as double-gate FinFETs and 3D circuits are being aggressively pursued for 65nm technology and beyond. Such aggressive scaling and new device structures give rise to several unique design issues which must be dealt with before any of these technologies will gain mainstream acceptance. We will discuss unique design aspects and issues resulting from this scaling such as power dissipation, gate-to-body tunneling, self-heating, reliability issues, and process variations. With an eye towards the future, design and CAD issues related to sub-65nm device structures such as double gate FinFET will be discussed.

Abstract:

High performance analog-to-digital converter (ADC) is a key circuit in today's signal processing systems, for commercials and defense systems. The ADC keeps extending its applications and performance with the development of new material, technologies, architectures, and circuit techniques. In particular, emerging telecom systems demand state-of-art high speed and high resolution ADCs. This talk deals with design aspects of today's most popular integrated ADC applications, technologies, architectures, and circuits. First I present an overview of the various ADC applications, technologies, architectures, and their performance limitations. I then discuss the design considerations for 10GSPS ADCs for optical receiver applications. Finally, I discuss the performance requirements of the ADCs in RF applications and show two ADC examples for IF sampling and even direct RF sampling receivers.

Abstract:

New advances in analog VLSI circuits have made it possible to perform operations that more closely reflect those done in DSP applications, or that are desired in future DSP applications. The recent explosion of advances in floating-gate technology fabricated in standard CMOS processes have resulted in analog circuits and systems that can be programmable, reconfigurable, and adaptive at a density comparable to digital memories. Therefore, one might wonder if we have both digital and analog signal processing available, how does one choose a particular solution for a given application. This talk will discuss our current research looks at these Cooperative Analog Digital Signal Processing (CADSP) systems that benefit from the advantages of both types of systems to make something better than the sum of its parts. We will also describe basic floating-gate circuits, programming methods of floating-gate circuits and systems, and how they enable a wide range of circuit and signal processing operations. We will describe approaches towards auditory and image signal processing applications, including programmable filters, noise suppression, analog signal processing front-end system for speech recognition, separable image transforms, and adaptive filters. These approaches offer the possibility of changing the way we see analog circuit design, as well as the future of analog and digital signal processing.

Abstract:

This presentation addresses observed phenomena obstructing circuit performance in the RF operation regime. The origin of the phenomena as well as their modeling will be discussed. To assist in the development of RF circuits, the most important issue is to guarantee sufficient simulation accuracy and applicability for any advanced technology. Under high-frequency operation, higher-order phenomena such as distortion as well as noise become serious for reliable circuit performance prediction. Here all such device phenomena are demonstrated to be determined by carrier dynamics, which are in principle observed in the I-V characteristics.

Abstract:

Lowering the energy consumed by an SRAM cache in active or standby mode is becoming increasingly difficult with scaling of transistor dimensions, operating voltages and cache densities due to limitations imposed by VT fluctuations in small-geometry cell transistors, by leakage due to thermal excitation and quantum tunelling, by soft-error and by wiring. This seminar will review fundamental limits on CMOS SRAM operating voltages imposed by binary signal quantization requirements, fluctuation limits on CMOS SRAM density imposed by random VT fluctuations of CMOS SRAM cell transistors and circuit techniques to reduce array leakage without impacting performance, density or noise margins.