Characteristics of reactive magnetron sputtered ZnO films

Highly oriented, dense, and fine-grain polycrystalline ZnO films with an excellent surface flatness have been produced. The thin films were deposited by DC conical reactive magnetron sputtering. X-ray scanning and scanning electron microscopy were used to evaluate film crystalline structure, and electromechanical measurements were used to measure piezoelectric properties. The relative importance of experimental parameters influencing the film formation and quality is as follows: substrate distance and location with respect to the cathode, quality of substrate surface, oxygen flow and pressure, plasma-discharge power, and substrate temperature. Excellent films have been produced on glass, on thermally oxidized Si substrates, and on clean metallic thin films. Films having c-axis orientation of up to 17° to the substrate normal have been successfully deposited on Al thin layers on Si-SiO₂ substrates by varying the substrate position with respect to the plasma. The best films produced on (111) Si had X-ray rocking curve half-widths of 0.9°