Annealing effects on contact properties of aluminum doped zinc oxide thin films

Aluminum Zinc Oxide (AZO) thin films are grown on glass substrates by RF Magnetron Sputtering using a single target of zinc oxide (99 wt%) and aluminum oxide (1 wt%) with argon as the plasma. Photolithographic process is then performed on the films in order to obtain a Transmission Line Model structure (TLM) of the metal contact system, namely aluminum and gold. The specific contact resistivity, rho(c), of these two metal-semiconductor systems, which will undergo different rapid thermal annealing (RTA) environment, are determined. X-Ray diffraction patterns for these samples are obtained to investigate phase formations or micro-structural changes so as to justify for the differences in specific contact resistivity obtained for these contact systems. The different RTA environment are simulated by purging either nitrogen or argon gas, with a pressure of 40 psi at a temperature of 400 degreesC for 60 s and annealing in vacuum (10(-6) Tort) also at the same temperature and duration, One-dimensional TLM (1D-TLM) measurements are performed on the TLM structures to obtain the specific contact resistivity. rho(c). Results show that aluminum contacts on AZO without RTA give the lowest rho(c) as compared to those in other environment, while gold contacts on AZO annealed in vacuum yield the lowest rho(c). Adhesion of aluminum contacts on AZO is good even when subjected to ultrasonic bath test but not true for the case of gold contact, which adheres poorly on AZO films.