Thin-film characterization using a scanning laser acoustic microscope with surface acoustic waves

The use of surface acoustic waves in a scanning laser acoustic microscope for the characterization of the mechanical or acoustic properties of thin films deposited on piezoelectric substrates is demonstrated. Quantitative measurements of mass loading effects of 5000-AA-thick tungsten films deposited on lithium niobate substrates were obtained using 100-MHz surface acoustic waves. No information about the tungsten film could be obtained using 100-MHz compressional waves. Methods of generating surface waves on nonpiezoelectric materials so that this technique could be used on arbitrary substrates are discussed.<
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