Impact of Direct Plasma Densification on Resistivity and Conformality of PEALD Tantalum Nitride

Abstract

A novel plasma enhanced atomic layer deposition (PEALD) process was demonstrated for tantalum nitride (TaN) based on the reduction of pentakis(dimethylamino)tantalum (PDMAT). High-power, direct plasma densification steps were incorporated into each PEALD growth cycle, resulting in ion bombardment of the TaN surface during growth. These densification steps enabled the deposition of low-resistivity, high-density TaN. Physical film densification by ion bombardment was confirmed from the observed thickness reduction of TaN deposited by PEALD with densification steps compared to PEALD without densification steps, for an equivalent number of PEALD cycles. In terms of PEALD TaN resistivity, ion-bombardment induced densification resulted in a reduction by an order of magnitude, from ~4000 μΩcm to ~400 μΩcm. In patterned trench structures, ion bombardment can achieve densification of PEALD TaN at the trench bottom while sidewall surfaces appear to show a less significant reduction in film thickness.