Investigation On (100) AlN/Diamond Substrate For High-frequency SAW

In recent years, radio frequency band is currently occupied by the increasingly tense,high-frequency communication device is moving in the development, there has been anincreasing interest in developing surface acoustic wave devices operating at high frequencies.Diamond has the highest SAW velocity among all solids, Combine piezoelectric materialswith diamond has become a research focus at home and abroad. traditional piezoelectricmaterials such as ZnO,LiNbO3,(002)AlN,with a sound velocity under4000m/s were usedto designed high frequency SAW devices, can not achieve the desired purpose of improvingthe frequency.Choose (100)AlN for the study because of its speed of sound is the highest among allpiezoelectric materials,about11354m/s, which is closest to the sound velocity of diamond. Soin this paper, the (100)AlN/diamond substrate of high frequency SAW was designed andanalyzed.In the present paper, AlN thin films were deposited on N-Si(100) substrate by a radiofrequency sputtering. And the grown AlN thin films were studied by X-ray diffraction andAtomic Force Microscopy. The growth parameters, such as pressure, sputtering power, N₂partial pressure and substrate-target spacing, on the texture degree of AlN thin films wereinvestigated. Meanwhile the effects of in-situ annealing and in-situ annealing ended by N₂onthe crystal orientation of were studied, respectively. The most suitable conditions in favor ofAlN (100) orientation priority growth were as follows: the substrate-target was8㎝,sputtering power75w, pressure1.2Pa, substrate temperature350℃,proportion of nitrogenand argon was8:12, and in-situ annealing. In addition, impacts on preferred orientation ofAlN thin films were also discussed within the perspectives of molecular average free distanceand energy.Please look at the following innovation theory:1. Be the first to depositing the high sound velocity (100)AlN piezoelectric material ondiamond, which will lessen frequency dispersion of sound velocities between AlN anddiamond and enhance frequency of SAW devices.2. Moreover, the peak value of AlN (100) orientation was improved by combination ofultrahigh vacuum radio frequency sputtering and in situ annealing ended by N₂. And thesurface roughness was also minished. So the high performance multilayer piezoelectricmaterials "(100) AlN/diamond" were realized.