Chemical vapor deposition–physical vapor deposition aluminum plug process for dynamic random-access memory applications

Abstract

The integrated chemical vapor deposition (CVD)–physical vapor deposition (PVD) Al plug process was successfully applied to capacitor-over-bit-line-type dynamic random-access memory process flow for the simultaneous formation of plugs and wires. The CVD-PVD Al film completely filled re-entrant vias with aspect ratios up to 10:1, and Al plugs showed lower via resistance compared with that of conventional W plugs. The PVD Al temperature can be as low as 350 °C, which is compatible with most low-dielectric-constant intermetal dielectric materials. However, outgassing from the intermetal dielectric was critical to complete via filling of the CVD-PVD Al film, and the conventional degassing process was insufficient for eliminating outgassing from hydrogen silsesquioxane. Sufficient baking after the via etching was effective for eliminating outgassing, and complete via filling was achieved.