Cu(Mn) alloy seed BEOL studies revealed fundamental insights into Mn segregation and EM enhancement. We found a metallic-state Mn-rich Cu layer under the MnOx layer at the Cu/SiCNH cap interface, and correlated this metallic layer with additional EM enhancement. A carbonyl-based CVD-Co liner film consumed Mn, reducing its segregation and EM benefit, suggesting O-free Co liner films are strategic for Cu-alloy seed extendibility.

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.

Conformality studies on trench structures in oxide and porous low-k dielectrics as well as Cu trench fill evaluations have been conducted employing a plasma enhanced atomic layer deposition (PEALD) Ru liner process in conjunction with conventional physical vapor deposited (PVD) Ta(N). The conformal growth of Ru by PEALD was demonstrated, while the benefits of a Ru layer underneath a conventional PVD Cu seed layer for Cu trench fill enhancement were shown. Poor PVD Cu seed layer coverage is considered to be the prime cause of the poor Cu/liner interface quality observed in the case of conventional Ta(N)/Cu liner/seed processes. Detailed EELS/EDX analysis has confirmed the presence of TaOx at the Ta(N)/Cu interface which is anticipated to be a key contributing factor impacting reliability performance.