Optimization of Oxygen Annealing Process to Increase the Work Function of Mo/Ti or Cu/Ti Film by Inserting Partially Oxidized Thin Layer at Surface Region

Abstract

The Oxygen (O-2) annealing processes of metal electrode in rapid thermal annealing (RTA) and furnace were applied to modify surface properties including work function and bonding state without change in bulk properties. The Mo/Ti (50/3 nm) and Cu/Ti (50/3 nm) films were annealed at different temperature in RTA and furnace, and the film properties of them were characterized with various analytical tools to optimize annealing condition. At high annealing temperature, both Mo/Ti and Cu/Ti films were fully oxidized and bulk properties of them such as resistivity, crystallinity and morphology also changed. But the metal electrode annealed at specific annealing temperature showed distinctive behavior that the binding energy and work function only changed without change in bulk properties. During annealing process, the oxidation reaction is gradually proceed when the oxygen gas of sufficient energy contact metal atom at surface region and diffuses from surface region to bulk region of metal film. For one example, the work function of Mo/Ti film annealed at 300 degrees C in RTA increased from similar to 4.6 eV to similar to 5.2 eV, but the bulk properties such as sheet resistance (similar to 31.6 /square), roughness (0.951 nm) and crystallinity were maintained to similar characteristics with those of as-deposited Mo/Ti film. (C) 2012 The Electrochemical Society. [DOI: 10.1149/2.048206jes] All rights reserved.