The Deposition And Character Of H-BN/Si And H-BN/Diamond Multilayer Structure Films For SAW Device

With the development of society and the progress of technology, acoustics which is ancient and extremely with vigor has already permeated many disciplines and our daily lives, particularly has obtained the widespread application in electronic information domain, the surface acoustic wave (SAW) technology is the acoustics and electronics combination of a Frontier Science, acoustic-electric transducer is the emergence of a powerful impetus to the development of acoustics and electronics.In recent years, with the rapid development of mobile communications, the traditional SAW materials and process conditions can no longer meet the high operating frequency and have the ability to withstand high-power, high sound velocity, high electro-mechanical coupling coefficient, low insertion loss, high temperature stability and other characteristics of requirements, this time, multi-layer structure SAW devices with their excellent characteristics aroused extensive attention.This paper discussed the basic working principle of SAW devices, analyzed and compared the characteristics of several piezoelectric materials (LiNbO3, ZnO, AlN and h-BN) for SAW devices. After giving full consideration to the current applications of the device, we decided to use h-BN as piezoelectric material for SAW devices.First, boron nitride films for SAW devices were deposited on Si wafers by RF magnetron sputtering. The purity and orientation of h-BN in the Films was investigated. RF magnetron sputtering processes were optimized using orthogonal experiments. Sputtering time was fixed at 2 hours, the distance from target to substrate was 6 cm, and the working pressure was 0.75 Pa. The boron nitride films were characterized by Fourier transform infrared(FTIR)spectroscopy, X-ray diffraction spectra(XRD) and atomic force microscope,(AFM). Based on the experimental results, the optimized fabrication parameters of high purity and c-axis oriented h-BN films by RF magnetron sputtering are shown as following: the substrate temperature of 400℃, the N 2:Ar ratio of 7:8(vol.%), the sputtering power of 300 W and the substrate negative bias of 0 V.Second, boron nitride films were deposited on diamond wafers, and the processes were optimized using orthogonal experiments also.By optimizing the deposition process on silicon and diamond substrates by two kinds of h-BN thin film, we obtained high purity and c-axis oriented h-BN films for the development of 2.5GHz or above SAW devices to create the conditions.