Low-Temperature Fabrication of High-Quality Silicon Oxide Thin Film by RF Sputtering

Abstract

Low-temperature fabrication of thin-film dielectric is essential in various applications, including flexible/stretchable electronics, monolithic 3D device, and large-area sensor/display. Silicon dioxide (SiO2) is one of the most extensively used dielectric materials, but conventional deposition methods, such as plasma-enhanced chemical vapor deposition and atomic layer deposition, require relatively high temperature. In this study, a high-quality SiO2 thin film was fabricated at low temperature below 150 °C using sputter deposition and plasma treatment. As additional oxygen flow during sputtering reduced the fraction of unstable strained SiO2, a 30-nm-thick thin film exhibited low leakage current (3×10-7 A/cm2 at 3 MV/cm) and high breakdown field (11.33 MV/cm). After an optimized hydrogen plasma treatment, the interface trap density between Si and sputtered SiO2 was minimized to be 7×1011 cm-2eV-1, which is comparable to thermally grown SiO2. X-ray photoelectron spectroscopy and secondary ion mass spectroscopy at the interface confirmed that the hydrogen plasma process effectively passivates dangling bonds and reduces the portion of oxygen-deficient species, such as Si2O3, SiO, and Si2O. The hysteresis curve of IGZO thin film transistors (TFTs) with sputtered SiO2 showed our SiO2 has the outstanding interface characteristics with IGZO, which the most promising semiconductor material for future devices.