Simulation And Preparation For IDT/AlN/Diamond Multilayer Films Of Surface Acoustic Wave

For the preparation of IDT/AlN/Diamond mutilayer membrane structure of SAW filters with high frequence(2.5GHz) and large power, we have done modal and harmonic analysis on IDT/AlN and IDT/AlN/Diamond structures using the piezoelectric analysis in ANSYS multiphysics envirionment. Some conclusions are obtained. For IDT/AlN structure, its resonance frequence is 1.248GHz in short circuit case, and the anti-resonance frequence is 1.266GHz in open circuit case. The phase velocity of SAW is 5028m/s. The effective electromechanical coupling coefficient (K~2) is 3.6% and the equivalent resistance is 0.5mΩ. For IDT/AlN/Diamond structure, its resonance frequence is 2.4936GHz in short circuit case, and the anti-resonance frequence is 2.562GHz in open circuit case. The phase velocity of SAW is 9911m/s and K2 is 5.8%.Then a series of AlN films with preferred c-axis orientation were deposited on Si or Diamond substrates using the radio frequency (RF) magnetron sputtering method under the different substrate to target distance, substrate temperature, the component ratio between N2 and Ar, RF power and different cooling post-processings. Finally, the optimal FWHM of (002)AlN/Si structure is 0.252°. Moreover, we also got some other conclusions as follows. Firstly, with the increasing of N~2 concentration and RF power, or the decreasing of substrate temperature, (002)AlN peak increased while FWHM inclined. Secondly, there was the competant growth between the group of (100) and (002) peaks and the group of (100) and (002) peaks with the decreasing of substrate to target distance. Lastly, from the perspective of the crystal plane and substrate-film adherence, AlN film with highly preferred c-axis orientation was obtained by cooling in low vacuum under deposition gas ambient. However, the maximum values of the hardness and Young's modulus were reached in that case. In summary, AlN films with preferred c-axis orientation were deposited on following condition:substrate to target distance(5cm), substrate temperature(300℃), the component ratio between N2 and Ar(1:1), RF power(350W).Eventually, AlN films with preferred c-axis orientation were also deposited on Cu/Si structure and Diamond substrate successfully.