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Mapping of Thin Film Elastic Constants and Density Using a Scanning Phase-Measuring Acoustic Microscope

IP.com Disclosure Number: IPCOM000036724D
Original Publication Date: 1989-Oct-01
Included in the Prior Art Database: 2005-Jan-29
Document File: 2 page(s) / 49K

Publishing Venue

IBM

Related People

Meeks, SW: AUTHOR

Abstract

This invention is a new technique to map the elastic constants and density of a very thin film. This technique is applicable to films as thin as 10 angstroms. The method described here can map the density and elastic constants of thin film deposited on an anisotropic substrate with a lateral resolution of 5 microns. To accomplish this mapping a scanning phase-measuring acoustic microscope (SPAM) with a directional acoustic lens is required.

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Mapping of Thin Film Elastic Constants and Density Using a Scanning Phase-Measuring Acoustic Microscope

This invention is a new technique to map the elastic constants and density of a very thin film. This technique is applicable to films as thin as 10 angstroms. The method described here can map the density and elastic constants of thin film deposited on an anisotropic substrate with a lateral resolution of 5 microns. To accomplish this mapping a scanning phase-measuring acoustic microscope (SPAM) with a directional acoustic lens is required.

The maps of elastic constants and density are obtained by positioning the lens above the region of an anisotropic substrate where it has been covered with a thin film and measuring the phase versus angle by rotating the lens by 360o. This will give a curve of velocity or phase versus angle. This procedure is repeated at each point on the thin film to yield a map of the mechanical properties of the thin film. This set of measurements is compared with a similar set of measurements made on bare silicon in order to extract the elastic constants and density of the thin film. This scheme is illustrated in the figure, which shows the unperturbed Rayleigh wave curve (solid line) taken on the bare silicon and the perturbed Rayleigh wave curve (dashed line) taken in the region where the thin film covers the silicon. The perturbed Rayleigh wave velocity is related to the elastic constants and density of the thin film by the equation below. where p' and m', g' are the density and Lame constants, respectively, of the thin ...