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High-resolution picosecond acoustic microscopy for non-invasive characterization of buried interfaces

Published online by Cambridge University Press:  01 May 2006

Shriram Ramanathan  and
David G. Cahill
Shriram Ramanathan*
Affiliation:
Components Research, Intel Corporation, Hillsboro, Oregon 97124
David G. Cahill
Affiliation:
Department of Materials Science and Engineering and Frederick Seitz Materials Research Laboratory, University of Illinois, Urbana, Illinois 61801
*
a) Address all correspondence to this author.Present address: Division of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138. e-mail: Shriram@deas.harvard.edu
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Abstract

Non-destructive investigation of buried interfaces at high-resolution is critical for integrated circuit and advanced packaging research and development. In this letter, we present a novel non-contact microscopy technique using ultrahigh frequency (GHz range) longitudinal acoustic pulses to form images of interfaces and layers buried deep inside a silicon device. This method overcomes fundamental limitations of conventional scanning acoustic microscopy by directly generating and detecting the acoustic waves on the surface of the sample using an ultrafast pump-probe optical technique. We demonstrate our method by imaging copper lines buried beneath a 6-μm silicon wafer; the lateral spatial resolution of 3 μm is limited by the laser spot size. In addition to the high lateral spatial resolution, the technique has picosecond (ps) time resolution and therefore will enable imaging individual interconnect layers in multi-layer stacked devices.

Keywords

BondingScanning acoustic microscopy (SAM)Thin film
Type
Articles
Information
Journal of Materials Research , Volume 21 , Issue 5 , May 2006 , pp. 1204 - 1208
Copyright
Copyright © Materials Research Society 2006

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