Texture formation in Ti–Ta alloy disilicide thin films

Abstract

Texture development in (Ti,Ta)Si2, formed from Ti–Ta alloy (0–6 at. % Ta) thin films sputtered on Si(001) and poly-Si substrates, was studied using both in situ and ex situ x-ray diffraction. The addition of Ta fundamentally changes the C54 texture. At 6 at. % Ta, an effective composition for lowering the C49–C54 transformation temperature, films on both substrates develop a strong (010) texture normal to the film plane. Alloy films on Si(001) also exhibit an in-plane orientational relationship between the final C54 texture and the underlying silicon lattice. A pseudoepitaxial film relationship with the substrate may, therefore, be playing an important role in the C54 transformation process. For 32 nm films on single-crystal substrates, the in situ measurements show that significant evolution of the C54 texture occurs during the growth process, suggesting that those grains well oriented with respect to the Si substrate lattice have higher growth velocities. The possibility of a template effect by the C40 or metal-rich Ti5Si3 phase is also discussed on the basis of texture considerations.