A TCAD Simulation Analysis of NADGFET Oscillator with Metal and Dielectric Combination

This paper analyzes the design and simulation results of a 5-stage ring oscillator using a 180 nm length non-aligned double gate inverter (NADGI). The NADGI consists of p-channel and n-channel field effect transistors i.e., NADGPFET and NADGNFET, with a channel length of 40 nm. The performance of a 5-stage ring oscillator was investigated by taking a combination of metal work functions ($\phi$) and gate oxide dielectrics ($k$). In this work, three metals namely, gold ($\phi=5 \text{eV}$), molybdenum ($\phi=4.75 \text{eV}$), tungsten ($\phi= 4.5 \text{eV}$), and three gate oxide namely, HfO2 ($k =24$), SiO2 ($k = 3.9$), Si3N4 ($k= 7.2$), are taken. The product of dielectric constant and metal work function ($\phi$) is taken as a characterizing parameter. The structure of the NADGI and ring oscillator was designed and tested in Sentaurus sdevice mixed-mode environment. The simulation result shows, at a supply voltage of 1 V, the NADGI device with low-$k$ dielectric material, and metal work function of 4.5 eV, gives a highest frequency of oscillations i.e., 85 GHz, when compared to the other combinations. Thus, this paper concludes that NADGI with low-$k$ dielectric material and work function is suitable choice to get a larger frequency of oscillations.