Characterization of Ultrathin PEALD-Grown RuCo Films for Diffusion Barrier and Copper Direct-Plate Applications

Abstract

RuCo films have been grown by plasma enhanced atomic layer deposition (PEALD) and investigated as a novel direct plate liner for advanced copper metallization. The RuCo films were characterized by transmission electron microscope (TEM) and found to form solid solutions, unlike other PEALD-grown mixed-phase direct plate barriers. Electrochemical deposition of copper was carried out on RuCo films with thicknesses from 2 nm to 6 nm and a range of Ru:Co metal ratios. Copper migration through the films was measured by triangle voltage sweep (TVS) testing, and RuCo films <6 nm thick were found to have equivalent diffusion performance as that of PVD TaN. Thicker RuCo films were found to be less robust barriers, and this unusual result is discussed.