CONVENTIONAL FURNACE AND RAPID THERMAL ANNEALING OF COBALT FILMS ON SI(111)

Abstract

The effects of conventional furnace annealing (CFA) and rapid thermal annealing (RTA) on the interfacial reactions of thin cobalt films on Si(111) have been investigated. The low heating rates (about 10-degrees-C s-1) associated with CFA lead to impurity segregation at the silicide-Si interface during the initial stage of interfacial reactions, while segregation is absent for high heating rates (about 100-degrees-C s-1) associated with RTA. From examination by transmission electron microscopy (TEM), RTA promotes uniform formation of silicides and epitaxial growth of twin-structure CoSi2, causing an average grain size of about 50 nm and a surface coverage area of about 70% at 500-600-degrees-C for 100-600 s. In contrast. silicidation is retarded for CFA, and grain growth is preferred to formation of epitaxial CoSi2. The electrical characterization of low doping level silicided shallow junctions correlates well with the TEM examinations of the interfacial reactions by the respective annealing schemes.