Photonic Curing: Rapid Thermal Processing of Oxide Thin-film Transistors on Plastic

Abstract

Metal oxide semiconductors (e.g., In2O3, InZnO) are excellent materials for flexible electronics because they exhibit high carrier mobility in the amorphous phase. In particular, metal oxides obtained with solution-processing methods based on sol-gel inks are compatible with large-area roll-to-roll manufacturing, thus offering a cost-effective alternative to traditional gas-phase oxide deposition methods. However, sol-gel oxide semiconductors typically require high post-processing temperatures (≥400 °C) to efficiently convert hydroxides (M-OH) to an extensive metal oxide network (M-O-M), which enables high mobility. The high temperature required for the oxide conversion hinders their use on plastic substrates, so alternative thermal processing routes are being investigated. Photonic Curing is particularly well-suited for this application because it was designed to rapidly heat a thin film to several hundred degrees on a low-temperature substrate (e.g. plastic) without damaging the substrate [1]. Photonic curing is a type of flashlamp annealing that uses short, intense pulses of broadband light from a xenon flashlamp (200–1100 nm, typically 1–2 ms pulses delivering 1–5 J/cm2) to heat the near-surface of the device stack, while most of the plastic substrate remains near room temperature. This can be accomplished due to the rapid (nonequilibrium) nature of photonic curing. Photonic curing also has other advantages over traditional thermal processing methods, including compatibility with large-area, high-throughput roll-to-roll fabrication. In the past, photonic curing has been primarily used to cure printed metal films, but recently there has been significant interest in photonic curing oxide semiconductors.