Thin layer growth on cobalt surface in solutions simulating slurry chemistry for chemical mechanical polishing

Abstract

Cobalt is gaining strong attention as an alternative metal for very narrow interconnects of advanced LSIs. Cobalt interconnects are fabricated by a damascene process like in copper. Slurries for the chemical mechanical polishing contain both an oxidizer and a corrosion inhibitor, in addition to abrasives. To understand the chemistry of the cobalt surface exposed to slurries, we studied the development of a layer on cobalt surfaces in benzotriazole (BTA)–hydrogen peroxide (H2O2) aqueous solutions using in situ spectroscopic ellipsometry and a microfluidic optical cell specifically designed for this purpose. The layer growth mechanism is discussed in view of cobalt out-diffusion.