Thin‐Film Properties and Barrier Effectiveness of Chemically Vapor Deposited Amorphous WSix Film

Abstract

Thin‐Film properties and barrier effectiveness against copper (Cu) diffusion of a thin amorphous layer were investigated. The amorphous layer was deposited by the chemical vapor deposition (CVD) method using the chemistry with the activation energy determined to be 3.0 kcal/mol. The film has a low film stress, low electrical resistivity, and excellent step coverage. The resistivity of the amorphous layer increases with the deposition temperature, but the residual stress of the layer decreases with the deposition temperature. The structure is thermally stable up to at least 600deg;C, while the copper‐contacted Cu//Si structure with a 50 nm thick barrier is stable only up to 550°C. Moreover, the Cu/ junction diodes can sustain a 30 min thermal annealing up to 500°C without causing degradation in electrical characteristics. Barrier failure of the layer in the Cu//Si structure at temperatures above 550°C is attributed to Cu atoms diffusion via fast paths in the layer. These fast paths were presumably developed from grain growth of the layer and/or thermal‐stress‐induced weak points in the layer.