Characterization of nanomechanical and piezoelectric properties of AlN thin film for thin film bulk acoustic wave resonators

In last few years, with the strong progress in thin film technologies for complex materials systems such as PZT, ZnO and AlN, thin film bulk acoustic wave resonator (FBAR) and filter concepts are gaining more and more importance for microwave frequency control applications. For resonators operating in the GHz range, piezoelectric thin film layer in the order of a few microns with desirable electromechanical properties (high Q and wide bandwidth) is required. Among these materials, AlN is very attractive due to that it has a number of interesting properties such as high thermal conductivity, high electrical insulation, and highly chemical stability. These characteristics make it possible to design and fabricate high frequency resonators and bandpass filters for signal processing and communication devices. If the thin film bulk acoustic resonator devices of sufficient performance can be fabricated, they will be the best choice to replace the current crystal, ceramic or SAW devices due to their compactness and good compatibility with the high frequency Si or GaAs integrated circuit processing. In this research, onchip AlN thin film resonator has been investigated. AlN thin films with 0.5 to 2.5 mu m thickness and c-axis orientation have been deposited by DC magnetron reactive sputtering method on silicon and sapphire substrates. The nanoindentation and laser interferometer methods are used to characterize the mechanical properties and electromechanical properties of the thin AlN film in the composite resonator structure. Patterning of AlN film and electrode layers has also been studied for the fabrication of onchip thin film bulk acoustic wave resonators.