Thermal and oxidation stability of Ti_<i>x</i>W_1−<i>x</i> diffusion barriers investigated by soft and hard x-ray photoelectron spectroscopy

The binary alloy of titanium-tungsten (TiW) is an established diffusion barrier in high-power semiconductor devices, owing to its ability suppress the copper from metallisation scheme into surrounding silicon substructure. However, little known about response TiW high temperature events or behaviour when exposed air. Here, a combined soft and hard X-ray photoelectron spectroscopy (XPS) characterisation approach used study influence post-deposition annealing titanium concentration on oxidation 300~nm-thick film. combination both XPS techniques allows for assessment chemical state elemental composition across surface bulk layer. findings show that high-temperature annealing, segregates out mixed metal system upwardly migrates, accumulating at TiW/air interface. Titanium shows remarkably rapid under relatively short timescales extent enrichment increased through longer periods by increasing precursor concentration. Surface enhances due strong gettering titanium. Quantification spectra highlights formation three tungsten environments, attributed WO$_2$, WO$_3$ oxide coordinated with environment. This combinatorial provides valuable insights thermal stability alloys two depth perspectives, aiding development future device technologies.