In Situ Annealing Behavior of Cu Thin Films Deposited over Co-W Diffusion Barrier Layers

Abstract

The development of new materials for the electronics industry has been in focus in recent years, as circuit miniaturization poses challenges for conventional solutions. Dewetting of Cu films over diffusion-barrier layers has fostered an interest in developing new solutions with lower interfacial energies, to withstand processing and service life. Co-W is a candidate material for seedless Cu-interconnect deposition, but its behavior during annealing is still not properly addressed. This study used an in situ scanning-electron-microscopy (SEM) approach to assess how heating rates affect dewetting behavior, as well as to determine the limits of annealing of 40 nm-thick Cu films deposited over this substrate. The 10 °C/min heating rate used showed copper dewetting starting at 450 °C, whereas the higher 30 °C/min rate induced dewetting at 400 °C. The Cu film deposited over Ta exhibited slightly different dewetting, with its onset starting earlier, but developing a slower progression throughout the temperature range analyzed in the annealing treatments.