Nanoscale CoSi2 contact layer growth from deposited Co/Ti multilayers on Si substrates

In this letter, we describe procedures for forming continuous, planar, and thermally stable 12-nm-thick CoSi2 layers via Co/Si interaction through an interfacial Ti(O) diffusion barrier layer. Three Co and three Ti layers were deposited sequentially on Si-(100) substrates by dual source thermal evaporation with Ti as the first layer. Oxygen was found to be selectively incorporated into all Ti layers during deposition. Following a 550 °C, 2 h anneal the morphology of the silicide layer depended strongly on the thickness of the initial Ti(O) layer. For an initial Ti(O) layer of ∼5 nm, both Co and Si readily diffused to form a Co silicide interfacial layer with a very rough, faceted interface. Increasing the Ti(O) thickness to ∼10 nm stopped Si out diffusion and reduced Co in diffusion such that a uniform 6 nm CoSix interfacial layer formed. Selective removal of the upper layers and a 750/800 °C annealing produced a 12 nm CoSi2 layer with a resistivity of ∼28 μΩ cm.