title: Electromechanical coupling constant extraction of thin-film piezoelectric materials using a bulk acoustic wave resonator.
abstract: Thin-film piezoelectric materials such as ZnO and AlN have great potential for on-chip devices such as filters, actuators and sensors. The electromechanical coupling constant is an important material parameter which determines the piezoelectric response of these films. This paper presents a technique based on the Butterworth Van-Dyke (BVD) model which, together with a simple one-mask over-moded resonator, can be used to extract the bulk, one-dimensional electromechanical coupling constant K(2) of any piezoelectrically active thin-film. The BVD model is used to explicitly define the series resonance, parallel resonance, and quality factor Q of any given resonating mode. Common methods of defining the series resonance, parallel resonance, and Q are shown to be inaccurate for low coupling, lossy resonators such as the over-moded resonator. Specifically, an electromechanical coupling constant K(2) of (2.6+/-0.1)% was measured for an (002) c-axis textured AlN film with an X-ray diffraction rocking curve of 7.5 degrees using the BVD based extraction technique.
authors.affiliation: Massachusetts Institute of Technology, Cambridge, MA 02139 , USA. rajan@mtl.mit.edu
authors.forename: R S
authors.initials: RS
authors.lastname: Naik
authors.forename: J J
authors.initials: JJ
authors.lastname: Lutsky
authors.forename: R
authors.initials: R
authors.lastname: Reif
authors.forename: C G
authors.initials: CG
authors.lastname: Sodini