Nitride-mediated epitaxy of CoSi2 on Si(001)

Epitaxial layers of CoSi2 have been grown on Si(100) by the technique of nitride-mediated epitaxy. An ultrathin layer of silicon nitride was formed on the Si(001) surface by exposure to ammonia gas at 900 degreesC, followed by the deposition of a layer of Co similar to20 A in thickness at room temperature. The sample was then annealed at 600 degreesC and the microstructure monitored by in situ transmission electron microscopy and diffraction. The formation of epitaxial islands of CoSi2 was observed directly, with no evidence of the formation of intermediate phases. The CoSi2 islands were found to be elongated along the in-plane Si<110> directions, consistent with reports of the deposition of Co by molecular beam epitaxy on clean Si(100) at low deposition rates and elevated temperature. This technique of silicidation may be of particular interest in the fabrication of advanced devices incorporating multilayer oxide/nitride gate stacks. (C) 2003 American Institute of Physics.