Application of AES micro-analysis to interface characterization in TiSi diffusion couples: 2—Influence of oxygen

Abstract

The diffusion of both silicon and oxygen in TiSi couples annealed at 600–700°C under low (pO2 = 10−4 Torr) or high (i.e. in air) oxygen pressures has been studied by AES depth profiling. The AES quantitative analysis of titanium and oxygen was based on the computation of the peak height to background ratios vs. concentration curves for the Ti-L3M23M23; Ti-Li3M23M45 and O-KL2L3 peaks. The element analysis was correlated with the peak shape and EELS spectra. The diffusion of oxygen from the free surface of the sample within the titanium film slows down and eventually stops the extension of the titanium silicide layer formed by diffusion of silicon from the wafer. The former results in the formation of titanium oxides (i.e. TiO, Ti2O3, or TiO2) and the latter in that of titanium silicides (mainly Ti5Si3, and TiSi2). For long enough diffusion times, the main silicide in the diffusion zone is TiSi2 and its growth rejects oxygen in the titanium-rich part of the couple. Therefore, the TiSi2/Si interface is almost free of oxygen.