Capacitance enhancement of Ru/ZrO2/Ru metal–insulator–metal capacitors via the annealing-induced densification of the top Ru electrode

Abstract

Ru films deposited via atomic layer deposition (ALD) typically exhibit island-like growth on oxide substrates, which degrades their mechanical and electrical properties. The reduction of structural defects in Ru films (including voids within the film bulk and loose bonds at the electrode/dielectric interface) by electrode annealing can increase the capacitance of Ru/ZrO2/Ru capacitors. However, the post-deposition annealing (PDA) of Ru electrodes in such capacitors has not been examined in detail. The capacitance enhancement of Ru/ZrO2/Ru capacitors was investigated by annealing their top Ru electrodes, which led to film densification. Structural and electrical analyses involving X-ray reflectivity, transmission electron microscopy, and adhesion tests revealed that annealing-induced densification of the Ru film lowered the film resistivity and strengthened interfacial adhesion. Consequently, PDA of the ALD-Ru top electrode resulted in an 11–16% increase in the capacitance of Ru/ZrO2/Ru capacitors compared to those with an as-deposited Ru top electrode.