Thermal Stability of CoSi2 on Single Crystal and Polycrystalline Silicon

Abstract

ABSTRACTThe thermal stability of Co silicide on single crystal and polycrystalline Si has been investigated. Co films were evaporated onto (100) Si and undoped polycrystalline Si and annealed in vacuum. Resulting silicide films were examined using Rutherford backscattering spectroscopy, scanning electron microscopy, electron-induced x-ray spectroscopy, and sheet resistivity measurements. We find that CoSi2 on single crystal (100) Si remains stable through 1000°C. In contact with undoped polycrystalline Si, intermixing begins at temperatures as low as 650°C for 30min annealing. The Co silicide and Si layers are intermixed after 750°C 30min annealing, giving islands of Si surrounded by silicide material, with both components extending from the surface down to the underlying oxide layer. The behavior of CoSi2 contrasts with results reported for TiSi2 which agglomerates on single crystal Si around 900°C but is stable on polycrystalline silicon as high as 800°C. Resistivity measurements show that the Co silicide remained interconnected despite massive incursion by Si into the silicide layer.