Deuterium-enabled stabilization of metal/oxide interfaces via suppressed oxygen diffusion in BEOL-compatible InGaZnO thin-film transistors

Abstract

This study systematically investigates the influence of post-metallization annealing (PMA) ambient on the electrical and interfacial properties of a-IGZO thin-film transistors (TFTs) incorporating BEOL-compatible tungsten (W) contacts. The devices were annealed at 300 °C and 350 °C using oxygen rapid thermal annealing (O₂ RTA) and high-pressure deuterium annealing (HPDA). The HPDA-treated devices exhibited enhanced electrical performance, including reduced subthreshold swing (74 mV dec⁻¹), increased I_on/I_off ratio, and lowered contact resistance (R_CW = 5.74 Ω cm). These improvements are attributed to the passivation of interfacial defects and the formation of W–D bonds, which effectively suppress interfacial oxidation. Furthermore, based on density functional theory (DFT) calculations, it was noted that HPDA promotes W–D bond formation, which can play an important role as an oxygen diffusion barrier. These theoretical results give a physical basis for the dual role of deuterium in defect passivation and suppression of interfacial oxidation at the W electrode, consistent with the HPDA observations of decreased W 4f binding energy and reduced WO_x formation.