Novel Complete Probabilistic Models of Random Variation in High Frequency Performance of Nanoscale MOSFET

Rawid Banchuin

doi:10.1155/2013/189436

Abstract

The novel probabilistic models of the random variations in nanoscale MOSFET's high frequency performance defined in terms of gate capacitance and transition frequency have been proposed. As the transition frequency variation has also been considered, the proposed models are considered as complete unlike the previous one which take only the gate capacitance variation into account. The proposed models have been found to be both analytic and physical level oriented as they are the precise mathematical expressions in terms of physical parameters. Since the up-to-date model of variation in MOSFET's characteristic induced by physical level fluctuation has been used, part of the proposed models for gate capacitance is more accurate and physical level oriented than its predecessor. The proposed models have been verified based on the 65 nm CMOS technology by using the Monte-Carlo SPICE simulations of benchmark circuits and Kolmogorov-Smirnov tests as highly accurate since they fit the Monte-Carlo-based analysis results with 99% confidence. Hence, these novel models have been found to be versatile for the statistical/variability aware analysis/design of nanoscale MOSFET-based analog/mixed signal circuits and systems.

Highlights

Nanoscale MOSFET has been adopted in many recently proposed analog/mixed signal circuits and systems such as high speed amplifier [1,2,3], millimeter wave components [4,5,6], and analog-to-digital converter [7,8,9]
Imperfection in MOSFET’s properties at the physical level, for example, random dopant fluctuation, line edge roughness, and so forth, causes the fluctuations in many of its characteristics such as threshold voltage, Vt, channel width, W, and channel length, L, which in turn yields the random variations in its circuit level parameters, for example, drain current, Id, transconductance, gm, and so forth
This means that high frequency performances of the nanoscale PMOS transistor is more robust to the random dopant fluctuation and process variation effects than that of NMOS one due to its lower Max[ΔCg/Cg,nom] and Max[ΔfT/fT,nom]

Summary

Introduction

Nanoscale MOSFET has been adopted in many recently proposed analog/mixed signal circuits and systems such as high speed amplifier [1,2,3], millimeter wave components [4,5,6], and analog-to-digital converter [7,8,9]. Imperfection in MOSFET’s properties at the physical level, for example, random dopant fluctuation, line edge roughness, and so forth, causes the fluctuations in many of its characteristics such as threshold voltage, Vt, channel width, W, and channel length, L, which in turn yields the random variations in its circuit level parameters, for example, drain current, Id, transconductance, gm, and so forth These variations are crucial in the statistical/variability aware design of MOSFET-based analog/mixed signal circuits and systems at the nanometer regimes since their magnitudes become relatively large percentages. There are many previous researches on analytical modeling of such variations, for example, [10,11,12,13] and so forth, on which the nanoscale CMOS technology has been focused They did not mention anything about variations in Cg and fT even though they exist and greatly affect the high frequency performances of the MOSFET-based circuits and systems. They have been found to be the versatile for the statistical/variability aware analysis/design of nanoscale MOSFET-based analog/mixed signal circuits and systems

The Proposed Models

The Verification

Discussion

Mathematical Tool for Reduced Computational Effort

Conclusion