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

Abstract

Cobalt is gaining a 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.