Weidong Liu

Bio: Weidong Liu is an academic researcher from University of California, Berkeley. The author has contributed to research in topics: MOSFET & Spice. The author has an hindex of 9, co-authored 15 publications receiving 830 citations.

BSIM4 gate leakage model including source-drain partition

Abstract: Gate dielectric leakage current becomes a serious concern as sub-20 /spl Aring/ gate oxide prevails in advanced CMOS processes Oxide this thin can conduct significant leakage current by various direct-tunneling mechanisms and degrade circuit performance While the gate leakage current of MOS capacitors has been much studied, little has been reported on compact MOSFET modeling with gate leakage In this work, an analytical intrinsic gate leakage model for MOSFET with physical source/drain current partition is developed This model has been implemented in BSIM4

An effective gate resistance model for CMOS RF and noise modeling

Abstract: A physics-based effective gate resistance model representing the non-quasi-static (NQS) effect and the distributed gate electrode resistance is proposed for accurately predicting the RF performance of CMOS devices. The accuracy of the model is validated with 2D simulations and experimental data. In addition, the effect of the gate resistance on the device noise behavior has been studied with measured data. The result shows that an accurate gate resistance model is essential for the noise modeling.

SOI thermal impedance extraction methodology and its significance for circuit simulation

Abstract: The buried-oxide in SOI MOSFET inhibits heat dissipation in the Si film and leads to increase in transistor temperature. This paper reports a simple and accurate characterization method for the self-heating effect (SHE) in SOI MOSFETs. The AC output conductance at a chosen bias point is measured at several frequencies to determine the thermal resistance (R/sub th/) and thermal capacitance (C/sub th/) associated with the SOI device. This methodology is important to remove the misleadingly large self-heating effect from the DC I-V data in device modeling. Not correcting for SHE may lead to significant error in circuit simulation. After SHE is accounted for, the frequency-dependent SHE may be disabled in circuit simulation without sacrificing the accuracy, thus providing faster circuit simulation for high-frequency circuits.

Modeling of pocket implanted MOSFETs for anomalous analog behavior

Abstract: Pocket implant is widely used in deep-sub-micron CMOS technologies to combat short channel effects It, however, brings anomalously large drain-induced threshold voltage shift and low output resistance to long channel devices This creates a serious problem for high-performance analog circuits In this paper, the first physical model of these effects is proposed and verified against data from a 018 /spl mu/m technology This model is suitable for SPICE modeling

Studying the impact of gate tunneling on dynamic behaviors of partially-depleted SOI CMOS using BSIMPD

Abstract: In this, work, we investigate and analyze the impact of gate tunneling on dynamic behaviors of partially depleted SOI CMOS with the aid of the physically accurate BSIMPD model. We examine in particular the impact of gate tunneling on the history dependence of inverter delays. The examination reveals key requirements for capturing the history effect in SPICE modeling. This study suggests that gate tunneling has a strong impact on the delay range and should be considered in SOI circuit simulation. It is crucial for circuit, designers to understand and contain the hysteretic delay variations caused by gate current. An accurate SPICE model that includes the oxide tunneling mechanism should be used to quantify the effect without undermining the performance benefit of a partially depleted SOI technology. BSIMPD is one model that attempts to bridge the gap between advanced SOI technologies and circuit design. With its built-in floating-body, self-heating and body-contact modules, BSIMPD captures SOI-specific effects and therefore is able to raise the design quality of PD SOI chips. BSIMPD has been implemented in Berkeley SPICE3f4 and other commercial SPICE simulators. It may also be the basis for computing the look-up tables used for higher-level timing simulation.

Leakage current mechanisms and leakage reduction techniques in deep-submicrometer CMOS circuits

Abstract: High leakage current in deep-submicrometer regimes is becoming a significant contributor to power dissipation of CMOS circuits as threshold voltage, channel length, and gate oxide thickness are reduced. Consequently, the identification and modeling of different leakage components is very important for estimation and reduction of leakage power, especially for low-power applications. This paper reviews various transistor intrinsic leakage mechanisms, including weak inversion, drain-induced barrier lowering, gate-induced drain leakage, and gate oxide tunneling. Channel engineering techniques including retrograde well and halo doping are explained as means to manage short-channel effects for continuous scaling of CMOS devices. Finally, the paper explores different circuit techniques to reduce the leakage power consumption.

Energy dissipation and transport in nanoscale devices

Abstract: Understanding energy dissipation and transport in nanoscale structures is of great importance for the design of energy-efficient circuits and energy-conversion systems. This is also a rich domain for fundamental discoveries at the intersection of electron, lattice (phonon), and optical (photon) interactions. This review presents recent progress in understanding and manipulation of energy dissipation and transport in nanoscale solid-state structures. First, the landscape of power usage from nanoscale transistors (∼10−8 W) to massive data centers (∼109 W) is surveyed. Then, focus is given to energy dissipation in nanoscale circuits, silicon transistors, carbon nanostructures, and semiconductor nanowires. Concepts of steady-state and transient thermal transport are also reviewed in the context of nanoscale devices with sub-nanosecond switching times. Finally, recent directions regarding energy transport are reviewed, including electrical and thermal conductivity of nanostructures, thermal rectification, and the role of ubiquitous material interfaces. Open image in new window

Energy Dissipation and Transport in Nanoscale Devices

Abstract: Understanding energy dissipation and transport in nanoscale structures is of great importance for the design of energy-efficient circuits and energy-conversion systems. This is also a rich domain for fundamental discoveries at the intersection of electron, lattice (phonon), and optical (photon) interactions. This review presents recent progress in understanding and manipulation of energy dissipation and transport in nanoscale solid-state structures. First, the landscape of power usage from nanoscale transistors (~10^-8 W) to massive data centers (~10^9 W) is surveyed. Then, focus is given to energy dissipation in nanoscale circuits, silicon transistors, carbon nanostructures, and semiconductor nanowires. Concepts of steady-state and transient thermal transport are also reviewed in the context of nanoscale devices with sub-nanosecond switching times. Finally, recent directions regarding energy transport are reviewed, including electrical and thermal conductivity of nanostructures, thermal rectification, and the role of ubiquitous material interfaces.

Thermal Modeling, Analysis, and Management in VLSI Circuits: Principles and Methods

Abstract: The growing packing density and power consumption of very large scale integration (VLSI) circuits have made thermal effects one of the most important concerns of VLSI designers The increasing variability of key process parameters in nanometer CMOS technologies has resulted in larger impact of the substrate and metal line temperatures on the reliability and performance of the devices and interconnections Recent data shows that more than 50% of all integrated circuit failures are related to thermal issues This paper presents a brief discussion of key sources of power dissipation and their temperature relation in CMOS VLSI circuits, and techniques for full-chip temperature calculation with special attention to its implications on the design of high-performance, low-power VLSI circuits The paper is concluded with an overview of techniques to improve the full-chip thermal integrity by means of off-chip versus on-chip and static versus adaptive methods

PSP: An Advanced Surface-Potential-Based MOSFET Model for Circuit Simulation

Abstract: This paper describes the latest and most advanced surface-potential-based model jointly developed by The Pennsylvania State University and Philips. Specific topics include model structure, mobility and velocity saturation description, further development and verification of symmetric linearization method, recent advances in the computational techniques for the surface potential, modeling of gate tunneling current, inclusion of the retrograde impurity profile, and noise sources. The emphasis of this paper is on incorporating the recent advances in MOS device physics and modeling within the compact modeling context