Oxidation behaviour of Cu thin films on Si wafer at 175-400°C

Abstract

Cu thin films have started to be used as the interconnection material in ultra-large-scale integrated (ULSI) circuits. Oxidation is a potential problem in this application. The present work studies the oxidation behaviours of Cu thin films in a multi-layered structure of Cu/TaN/SiO2/Si at temperatures from 175°C to 400°C in dry air. Below 250°C, Cu is oxidized to form Cu2O with a linear kinetics. Within ∼ 50 min, a compact, fine-grained oxide layer is formed to minimize further oxidation. Above 275°C, CuO forms following a parabolic rate law. The layer containing CuO is less protective than Cu2O. The oxidation products formed on Cu thin films are different from most previous reports on oxidation of bulk Cu metal. Oxidation mechanisms of thin Cu films were discussed based on the experimental results. © 2001 Elsevier Science B.V. All rights reserved.