Ultrathin Ni Silicides With Low Contact Resistance on Strained and Unstrained Silicon

Ultrathin Ni silicides were formed on silicon-on-insulator (SOI) and biaxially tensile strained SOI (SSOI) substrates. The Ni layer thickness crucially determines the silicide phase formation: With a 3-nm Ni layer, high-quality epitaxial NiSi(2) layers were grown at temperatures > 450 degrees C, while NiSi was formed with a 5-nm-thick Ni layer. A very thin Pt interlayer, to incorporate Pt into NiSi, improves the thermal stability and the interface roughness and lowers the contact resistivity. The contact resistivity of epitaxial NiSi(2) is about one order of magnitude lower than that of a NiSi layer on both As-and B-doped SOI and SSOI.