Analog/RF Performance Analysis of a-ITZO Thin Film Transistor

Abstract

This work reports RF and analog performance analysis of an amorphous Indium Tin Zinc Oxide thin film transistor. The various parameters affecting the performance of a-ITZO TFT like drain current, drain conductance, output resistance, transconductance, transconductance generation factor, early voltage, intrinsic gain, capacitances, cut off frequency, maximum frequency of oscillation, transconductance frequency product, gain frequency product, gain bandwidth product and gain transconductance frequency product have been closely examined. The device is further analyzed to investigate the impact of variation in physical parameters viz. dielectric material, dielectric thickness (𝐷𝑡) and temperature (T) on the RF/Analog performance. Use of high-k dielectric material in the simulated structure has resulted in low subthreshold slope (SS) of 0.62 V/decade, On voltage (𝑉𝑜𝑛) of - 0.29 V, 𝐼𝑜𝑛/𝐼𝑜𝑓𝑓 ratio of ~ 109, intrinsic gain (Av) of 104.5 dB and gain frequency product (GFP) of 1.86 GHz. The best results for dielectric thickness variation are obtained for Dt of 150 nm with SS of 0.22 V/decade, 𝑉𝑜𝑛 of -0.26 V, 𝐼𝑜𝑛/𝐼𝑜𝑓𝑓 of ~ 1010, Av of 175.69 dB and GFP of 2.39 GHz. In order to investigate device thermal reliability and stability, temperature analysis has also been done. To demonstrate the circuit level implementation of the simulated structure, a resistive load inverter circuit is simulated and analyzed for different variations (high-k, 𝐷𝑡 and T). It has also been concluded that TFT with high-k material or thinner dielectric at T=300 K provides best performance. This analysis confirms the potential of a-ITZO TFTs to realize high performance analog/RF circuits.