Analysis And Deposition Of AlN Films For High Frequency Multilayered SAW Devices

Diamond has excellent properties such as the highest E=1200Gpa,ρ=3.51g/cm3 and high SAW velocity(18000m/s), so CVD diamond were widely applied all because of its excellent physical properties. Amongst the varieties of applications of CVD diamond, the Surface Acoustic Wave (SAW) device is supposed to be one of the practical applications for its high SAW velocity.AlN is an importantⅢ-Ⅴcompound semiconductor material with wide band-gap, which has hexagonal wurtzite structure. Because of their excellent physical properties, AlN thin films were applied in blue-UV emitting materials, epitaxy buffer layer, and SAW device with GHz band. In the aspect of SAW Filter, for CVD diamond have very high SAW velocity, AlN thin films are piezoelectric films with high SAW velocity and good adhesion to CVD diamond. If AlN thin film was deposited on CVD diamond, the multiplayer film has not only high SAW velocity, but also has low temperature modulus (when the SAW device bears of high-power and the temperature rises, but the center frequency is very minor with the temperature power-up drift), which was suitable for SAWF of high frequency.In this paper, firstly, dense smooth diamond films were prepared by PJ CVD. The films were figured by some techniques such as SEM. The effects of underlayment material, deposition temperature of CVD diamond capacitors was investigated. The method of improving the density of nucleation by a diamond-like pre-coated layer in diamond preparation was obtained.Secondly, piezo-electric films AlN were deposited by magnetic sputtering. We have also explored the fabrication technology of AlN films. The AlN thin films are structurally analyzed using techniques such as Bragg X-ray diffraction to determine their crystal structure and composition distribution. We have investigated the deposition of AlN films on Si substrates, the effects of sputtering power, proportion of argon and nitride, sputtering temperature and sputtering pressure on microstructure and electricity performance of AlN thin films are also discussed. AlN/diamond multiplayer structure was prepared by RF magnetic control sputtering. We discussed effects of deposition parameters.In a word, based on a series of research, the paper discussed the effect of the deposition parameters of AlN thin films and CVD diamond, under the optimized condition highly property AlN films are fabricated which are suitable for the fabrication of SAW device.