CHARACTERISTICS OF HYDROGENATED ALUMINUM NITRIDE FILMS PREPARED BY RADIO-FREQUENCY REACTIVE SPUTTERING AND THEIR APPLICATION TO SURFACE-ACOUSTIC-WAVE DEVICES

Hydrogenated aluminum nitride (AlN:H) films have been deposited on sil icon wafers by the rf reactive magnetron sputtering method with H-2 ga s addition to Ar-N-2 gas mixture. The changes of physical properties o f AlN:H films with different H-2 gas addition have been examined by x- ray diffraction, scanning electron microscopy, and x-ray photoelectron spectroscopy. The surface acoustic wave (SAW) filters with wavelength of 60 mu m using these films have been fabricated and their SAW veloc ities and electromechanical coupling coefficients have also been measu red by a network analyzer. It is found that as the amount of H-2 addit ion increases, the surface of film becomes smooth, the stress is relie ved, the concentration of nitrogen atom increases and that of oxygen a tom decreases. We also found that AlN/AlN:H/AlN tri-layered films can prevent the blistering phenomena of AlN:H film. By measuring SAW chara cteristics of AlN/AlN:H/AlN tri-layered films, the SAW velocity is cal culated to be 5280 m/s and electromechanical coupling coefficient is 1 .35% which is the highest value reported so far. (C) 1997 American Vac uum Society.