Plasma-enhanced atomic layer deposition of hafnium silicate thin films using a single source precursor

Abstract

A single source precursor containing both Hf and Si was employed with oxygen plasma to deposit hafnium silicate thin films using plasma-enhanced atomic layer deposition (PEALD). The self-limiting growth features were observed between 210 °C-280 °C with a constant growth rate of 1.45 Å/cycle. The deposited hafnium silicate thin films were amorphous with a composition of Hf0.33Si0.66O2. The mechanism for the surface adsorption of the precursor was investigated by density functional theory (DFT) calculations, which show adsorption reactions of both Hf and Si atoms are viable. Bottom-gated InGaZnO channel thin-film transistors (TFTs) were fabricated to evaluate the electrical characteristics of PEALD hafnium silicate thin films as gate dielectrics. Compared to the conventional SiO2 gate dielectric, TFTs with PEALD hafnium silicate gate dielectric exhibited an improved switching performance, where the turn-on voltage, threshold voltage, saturation mobility, subthreshold slope, and on-off current ratio were −0.456 V, 3.202 V, 15.83 cm2/V·sec, 0.196, and 1.34 × 109, respectively.