Method of fabricating a highly conductive structure

Abstract

An improved method of fabricating a silicide structure includes depositing a metal, e.g., molybdenum or tungsten, directly onto a thin insulating layer of silicon dioxide and/or silicon nitride formed on a semiconductor substrate, co-depositing the metal and silicon onto the metal layer and then depositing silicon onto the co-deposited metal-silicon layer. This structure is annealed at a temperature sufficient to form a metal silicide between the thin insulating layer and the layer of silicon. The silicon layer serves as a source of silicon for the metal layer which is consumed during the annealing step to form, along with the co-deposited metal-silicon layer, a relatively thick metal silicide layer directly on the thin silicon dioxide layer. A sufficiently thick silicon layer is initially provided on the co-deposited metal-silicon layer so that a portion of the initial silicon layer remains after the annealing step has been completed. This excess silicon may be oxidized to form a passivating layer on top of the thick metal silicide layer. If all or a part of the silicon in the remaining silicon layer after annealing is removed, the thick metal silicide layer may be exposed to an oxidizing ambient for self-passivation. In this latter instance, the pure metal precipitates in the silicide resulting in a line with even greater conductivity than a pure silicide line, which is very desirable for interconnections.