Metal silicides synthesized by high current metal–ion implantation

Abstract

High current metal–ion implantation by a metal vapor vacuum arc ion source was conducted to synthesize some metal silicides, which are important candidates as materials in microelectronics. It was found that C54-TiSi2, ZrSi2, NiSi2, CoSi2, β-FeSi2, NbSi2, and TaSi2 layers on Si wafers with good electric properties could be obtained directly after implantation at relatively low formation temperature and that the formation of α-FeSi2, NbSi2, TaSi2, tetragonal WSi2, and tetragonal MoSi2 required additional postannealing to improve their crystallinity as well as their electric properties. Interestingly, NiSi2 layers of superior crystallinity and thus electric property were obtained for the first time by Ni ion implantation with a selected current density of 35 μA/cm2, which heated the Si wafers to a specific temperature of 380 °C. Under such formation conditions, the lattice mismatch between the growing NiSi2 and the Si substrate was calculated to be zero. The resistivity of the NiSi2 layers obtained was much lower than that of the Ni disilicide synthesized by a solid-state reaction that required a formation temperature of over 750 °C. The formation mechanism of the metal silicides studied and their associated electrical properties are also discussed.