Chemical Mechanical Polishing of Al and SiO2 Thin Films: The Role of Consumables

Abstract

Chemical mechanical polishing (CMP) studies of blanket aluminum, patterned aluminum, and thin films using a commercial slurry based on abrasive particles are presented. Both silicon dioxide and aluminum blanket films were polished with two pads of different hardness and structure. The removal rate and the dependence of the removal rate on pressure and linear velocity for both materials varies significantly with pad type. For the softer pad, the Al removal rate depends critically on the surface saturation of the pad with slurry particles. Scanning electron microscopy and X‐ray photoelectron spectroscopy were used to study the texture and chemical composition of the soft pad after different polishing conditions. We found saturation of the pad surface with particles but no metallic aluminum on the pad after CMP. Pad reconditioning causes the removal of the abrasive particles from the pad surface. Patterned aluminum samples with a TiN barrier layer were polished in alumina slurry with and without hydrogen peroxide using the soft pad. During CMP of microstructures, both Al and TiN must be removed at similar rates. The removal rate of the TiN film is dramatically enhanced when is incorporated into the slurry, whereas polishing of aluminum thin films showed that the oxidizer has no effect on the Al removal rate. Passive soaking of TiN in slurry revealed that TiN readily dissolves in the presence of a strong oxidizer, which increases the chemical component of the CMP process. © 1999 The Electrochemical Society. All rights reserved.