THE Ti / c - Si SOLID STATE REACTION III . The low - temperature reaction kinetics

Thin Ti layers (10 nm) are grown on top of a clean Si(ll1) substrate. Heating these layers initiates a solid state reaction, yielding a monosilicide phase at 350 o C and a C49 disilicide at 450 o C. The present study concerns the growth kinetics of both phases by means of ellipsometry. A diffusion-limited growth kinetics is found for the monosilicide formation. However, two growth rates are observed, a fast initial one and a slow terminal growth rate. An enhanced Si diffusion in atomically disordered regions as compared to well ordered regions (grams or clusters) could be an explanation. From the measurements we have found a value of 2 X 1OK” cm’/s for the diffusion coefficient at 370 o C and an activation energy of 0.62 + 0.1 eV. Both values correspond to the fast process. Subsequently increasing the temperature to 450 o C permits the growth of the homogeneous C49 TiSi, phase. For this process, both planar layer growth and intermixing are observed, however, quantitative results could not be derived from the present study.