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

Abstract

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 CoSi_x 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.