Breakdown field enhancement of Si-based MOS capacitor by post-deposition annealing of the reactive sputtered ZrO_xN_y gate oxide

Abstract

Zirconium oxynitride (ZrO_xN_y) thin films were deposited on silicon (100) substrates by radio frequency-reactive magnetron sputtering in an argon–oxygen–nitrogen atmosphere. Post-deposition annealing (PDA) process was performed in argon ambient at various annealing temperatures (500, 600, 700 and 800 °C) for 15 min. Metal–oxide–semiconductor capacitors were then fabricated with aluminum as the gate electrode. The effects of PDA process on the thin film’s structural and electrical properties of the samples were investigated. The structural properties of the deposited films have been evaluated by atomic force microscopy, Fourier transform infrared spectroscopy and Raman spectroscopy. On the other hand, the electrical characterization of the film was conducted by current–voltage analysis. The Raman results revealed that (600–800 °C) annealed samples comprised of crystalline multiphase films (t-ZrO₂, fcc-ZrN and bcc γ-Zr₂ON₂). Interfacial layer consisted of Zr–Si–O, Si–O–N and Si–O phase was formed for all investigated samples, and interfacial layer growth was suppressed when annealed at lower temperatures (500 °C). Electrical result revealed that the sample annealed at a relatively low temperature of 500 °C has demonstrated the highest breakdown field which was attributed to the low surface roughness, the low interface trap and the highly amorphous multiphase film.