High-spatial-resolution sub-surface imaging using a laser-based acoustic microscopy technique

Oluwaseyi Balogun*, Garrett D. Cole, Robert Huber, Diane Chinn, Todd W. Murray, James B. Spicer

*Corresponding author for this work

Research output: Contribution to journalArticle

12 Scopus citations

Abstract

Scanning acoustic microscopy techniques operating at frequencies in the gigahertz range are suitable for the elastic characterization and interior imaging of solid media with micrometer-scale spatial resolution. Acoustic wave propagation at these frequencies is strongly limited by energy losses, particularly from attenuation in the coupling media used to transmit ultrasound to a specimen, leading to a decrease in the depth in a specimen that can be interrogated. In this work, a laser-based acoustic microscopy technique is presented that uses a pulsed laser source for the generation of broadband acoustic waves and an optical interferometer for detection. The use of a 900-ps microchip pulsed laser facilitates the generation of acoustic waves with frequencies extending up to 1 GHz which allows for the resolution of micrometer-scale features in a specimen. Furthermore, the combination of optical generation and detection approaches eliminates the use of an ultrasonic coupling medium, and allows for elastic characterization and interior imaging at penetration depths on the order of several hundred micrometers. Experimental results illustrating the use of the laser-based acoustic microscopy technique for imaging micrometer-scale subsurface geometrical features in a 70-μm-thick single-crystal silicon wafer with a (100) orientation are presented.

Original languageEnglish (US)
Article number5688416
Pages (from-to)226-233
Number of pages8
JournalIEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control
Volume58
Issue number1
DOIs
StatePublished - Jan 1 2011

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ASJC Scopus subject areas

  • Instrumentation
  • Acoustics and Ultrasonics
  • Electrical and Electronic Engineering

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