Effect of High-k Oxide on Double Gate Transistor Embedded in RF Colpitts Oscillator

Abstract

This paper present a comprehensive analysis of LC Colpitts Oscillator built around a DGMOS (Double Gate Metal Oxide Semiconductor) transistor using high-k technology. A mixed- mode simulation is involved, applying a quantum model to the device whereas the rest of the considered circuit is governed by Kirchhoff‟s laws. The quantum device model correspond to 2D numerical calculations based on self- consistent codes coupling Poisson and Schrödinger equation along the transport direction, considering an effective mass approximation. A comparison with Drift Diffusion model (DDM) is made in order to point out importance of quantum effect in this nanometer device. The impact of high-k oxide gate is investigated and analyzed; the results confirm that the high-k is an interesting alternative to reduce tunneling gate current of the DGMOS transistor but reach the same drain one. Considering the oscillator, our goal is focused on the analysis of its phase noise. The Linear Time Variant (LTV) model of phase noise is considered. It is based on the Impulse Sensitivity Function (ISF) which describes carefully the sensitivity of an oscillator to a parasite impulse current injection in different nodes of the circuit. The obtained results pointed out that the ISF function is sinusoidal and its period is nearly the same of the oscillator output signal for different dielectric oxide. It also states that the phase noise of a Colpitts oscillator is not affected by the use of the high-k materials. Finally this method, if extended, is a good tool to investigate a perturbation response on such circuits.