4E-5 Study of Temperature Coefficient of Frequency and Electromechanical Coupling Coefficient of X Band Frequency SAW Devices Based on AlN/Diamond Layered Structure

Abstract

Abstract_ In this work, we report about the study of electromechanical coupling coefficient (K 2 ) and temperature coefficient of frequency (TCF) of SAW devices based on AlN/diamond layered structure intended for the X band (8GHz). SAW devices operating in the range of 8 GHz were realized by the combination of the high velocity of the AlN/diamond layered structure and the high lateral resolution obtained using e-beam lithography (EBL). Due to high electrical resistivity of the AlN film, interdigital transducers with sub-micronic resolution were patterned by an adapted technological EBL process. The analyses of structural and morphological of the diamond and AlN layers by Xray diffraction, atomic force microscopy (AFM) were carried out. They showed the highly (002) preferential orientation of AlN film deposited on diamond layer and a very weak surface roughness of less than 1nm measured on the surface of AlN/diamond layered structure. The analysis of device performances in terms of K 2 and temperature stability were carried out and discussed. The dispersion of both parameters as a function of normalized thickness of AlN layer (kh AlN ) was experimentally determined, and showed the obtaining of electromechanical coupling coefficient up to 1.4% for normalized thickness kh AlN varying between 3 and 5. Concerning the TCF, the recorder values show a quasiparabolic behavior. This TCF behavior in such high frequencies will discussed taking into account the nature of the TCF of AlN and diamond layers separately.