Surface acoustic wave methods to determine the anisotropic elastic properties of thin films

Citation
Dc. Hurley et al., Surface acoustic wave methods to determine the anisotropic elastic properties of thin films, MEAS SCI T, 12(9), 2001, pp. 1486-1494
Citations number
35
Categorie Soggetti
Spectroscopy /Instrumentation/Analytical Sciences","Instrumentation & Measurement
Journal title
MEASUREMENT SCIENCE & TECHNOLOGY
ISSN journal
09570233 → ACNP
Volume
12
Issue
9
Year of publication
2001
Pages
1486 - 1494
Database
ISI
SICI code
0957-0233(200109)12:9<1486:SAWMTD>2.0.ZU;2-#
Abstract
We have developed experimental and analytical methods to measure the anisot ropic elastic properties of thin supported films. In this approach, surface acoustic waves (SAWS) were generated using a line-focused laser. Waves wit h frequency components up to 400 MHz were detected by a Michelson interfero meter. Dispersion relations for the SAW phase velocity were calculated from displacement waveforms acquired with source-detector separations of 5-15 m m. To determine film properties from the dispersion relations, we developed a new inversion algorithm based on the delta-function representation of th e fully anisotropic, elastodynamic Green function for wave propagation. Our methods were first applied to an elastically isotropic aluminium film on a n isotropic fused silica substrate. The results show the validity of our me thods and were in good agreement with literature values. The results also i llustrate various aspects of measurement uncertainty. The same SAW methods were used to examine a series of titanium nitride films on single-crystalli ne silicon wafers. The inversion results assuming orthotropic elastic symme try indicated that c(11) increased and c(13) decreased with increasing film thickness. Values for the film thickness determined by our analysis were i n good agreement with destructive measurements of the actual thicknesses.