Interdiffusion, Phase Transformation, and Epitaxial CoSi2 Formation in Multilayer Co/Ti‐Si(100) System

Abstract

Interdiffusion, phase transformation, and epitaxial formation in a Co/Ti multilayer‐Si(100) system have been investigated. Evaporated and sputtered Co/Ti multilayers were deposited on RCA‐cleaned and dilute Si(100) substrate. The multilayer system was then subsequently heat‐treated by a two‐step annealing process. An initial Ti(O) amorphous layer formed due to oxygen/carbon incorporation during the deposition, or a amorphous layer formed by solid‐state amorphization reaction. These interfacial layers evolved into a Co‐Ti(O)‐Si amorphous alloy which functioned as a diffusion membrane which controlled the phase formed during subsequent annealing. The Co‐silicide phase sequence was , and finally from 550°C to higher temperature. Preferentially oriented (311) formed as the dominant phase in the temperature range from 650 to 800°C. Epitaxial nucleated from the template layer and grew substantially during the high temperature second annealing. The resulting epitaxial layer exhibited superior thermal stability and a resistivity as low as 15 μΩ‐cm, even for nanoscale thicknesses. Interface impurity cleansing by Ti, uniform and slow Co supply through the interfacial amorphous membrane, and a positive effect of the capping layers throughout the process promoted preferential (311) formation and subsequent epitaxial growth.