Accurate Extraction of Effective Gate Resistance in RF MOSFET

Ikkyun Jo,Toshimasa Matsuoka

doi:10.4236/cs.2015.65015

Abstract

This paper describes the gate electrode resistance of MOSFET and non-quasi-static (NQS) effect for RF operation. The vertical current paths between the silicide layer and poly-silicon are considered in the gate electrode. The vertical current paths are not effective in long-channel devices, but become more significant in short-channel devices. The gate resistance including vertical current paths can reproduce the practical RF characteristics well. By careful separation of the above gate electrode resistance and the NQS effect, the small-signal gate-source admittance can be analyzed with 130-nm CMOS process. Elmore constant (κ) of the NQS gate-source resistance is about five for long-channel devices, while it decreases down to about three for short-channel devices.

Highlights

CMOS device technology realizing low-power, large-scale integration and low-cost to manufacture is recently matching demands for miniaturization, low-power operation in wireless communication systems [1]-[4]
One of the important issues of the MOSFET model in RF operation is related to effective gate resistance which influences input impedance, maximum oscillation frequency fmax, and noise performance [9]-[11]
Gate electrode resistance of the MOSFET is composed of gate contact resistance between connecting the metal and silicide, resistance of the silicide itself, the interface resistance between the silicide and poly-silicon, (a) and vertical resistance of the poly-silicon itself [22]

Summary

Introduction

CMOS device technology realizing low-power, large-scale integration and low-cost to manufacture is recently matching demands for miniaturization, low-power operation in wireless communication systems [1]-[4]. Complexity of such a RF SoC increases, its short development time is always forced In such a situation, precise simulations of analog/RF circuits are important, and more accurate MOSFET model and analysis of parasitic elements are needed for their implementations [6]-[8]. Because the above two resistance factors have a different gate size dependence [18], their separate analysis is important in scalable MOSFET model and is useful in RF circuit design [8]. By careful separation of the gate electrode resistance and the NQS effect, the small signal gate-source admittance can be analyzed. From these values, the κ is derived.

Gate Electrode Resistance of MOSFET

Parameter Extraction for NQS Resistances

Verification of Gate Electrode Model and NQS Effect

Conclusion