Equilibration of non-stoichiometric Ta-Si deposits on polysilicon at high temperatures.

The formation of Tantalum Disilicide from either a metal-rich or silicon-rich amorphous film was studied to provide information on the kinetics of phase formation and the corresponding details of atom diffusion. A thin film structure consisting of ~3000angstroms of cosputtered Ta-Si on 4000angstroms of annealed polycrystalline silicon (poly Si) on ~1250angstroms of silicon dioxide was deposited over Si (100) wafers. The deposition variables probed were 1) Arsenic doped vs. undoped poly Si, 2) Si/Ta atom ratios of 3.2 and 1.3, and 3) capping silicon dioxide layers vs. no capping present during the anneals. One hour anneals were performed in vacuum between 850 and 1000C at 50C intervals. RBS and TEM measurements show that the metal rich film consumes an appropriate amount of poly Si to form the stable tantalum disilicide phase even at the lowest anneal temperature.