Evaluation of in situ formed W–Ti and MoSi2 as a diffusion barrier to Al for CoSi2 silicided contact

Abstract

A simple metallization process to form a shallow CoSi2 silicided contact and W–Ti diffusion barrier simultaneously has been developed. The process starts with depositions of a Co–Ti alloy layer and an overlying W layer on silicon wafers using a dual e-beam evaporation system; this is followed by a single-step annealing treatment in a normal flowing-nitrogen furnace. On the other hand, bilayer self-aligned shallow MoSi2/CoSi2/Si silicided contact can be derived from the W/Co–Mo/Si system by a two-step annealing treatment performed in the same environment. I–V characteristics for silicided p+n diodes with the diffusion barriers formed in situ were measured after they had been finished with Al deposition and post-Al annealing at temperatures from 350 to 600 °C in N2. For comparison, Al/CoSi2/p+n and Al/p+n structures were also investigated. It turns out that the integrity of Al/W–Ti/CoSi2/p+n and Al/MoSi2/CoSi2/p+n silicided contacts can be preserved up to 550 and 500 °C, respectively, for a 20 min annealing, while that of Al/CoSi2/p+n can be kept only up to 450 °C.