Stable tungsten disilicide contacts for surface and thin film resistivity measurements

Abstract

High-temperature stable electric contacts of tungsten disilicide (WSi2) on Si(001) are fabricated by a simple two-step process: vacuum deposition of W on the native Si dioxide and subsequent annealing under ultrahigh-vacuum conditions. Silicidation starts at 1000K, as, it is believed to occur, the Si diffuses to the surface through the defects in the oxide. Flash annealing to 1500K removes the oxide, resulting in stable WSi2 contacts on the surface. Contamination due to migrating W is confined to within a micrometer of the edge of the WSi2 contacts. Beyond this micrometer-sized zone, the surface is free of contamination as confirmed by low-energy electron microscopy and high-resolution low-energy electron diffraction. Reproducible resistance curves during annealing and cooling of the Si(001) sample confirm the reliability of the contacts, which can withstand many flash-annealing cycles without degradation.