Preliminary Draft Content

SCANNING ELECTRON ACOUSTIC MICROSCOPY

FOR MATERIALS CHARACTERISATION

W. K. Wong, J. C. H. Phang¹, J. T. L. Thong¹, Q. R. Yin², S. X. Hui² and W. P. Chua³

Institute of Materials Research and Engineering

3 Research Link

Singapore 117602

^{1 Centre for IC Failure Analysis and Reliability (CICFAR)
National University of Singapore
10 Kent Ridge Crescent
Singapore 119260}

^{2 Shanghai Institute of Ceramics,
Chinese Academy of Sciences (SICCAS)
1295 Dingxi Road
Shanghai 200050
P.R. China}

^{3 Scanning Beam Technology Pte. Ltd.
65 Science Park Drive
The Fleming
Singapore 118251

1. Summary

The Scanning Electron Acoustic Microscopy (SEAM) technique is a new operation mode for the Scanning Electron Microscope (SEM) that utilises thermo-acoustic contrast for sub-surface inspection. Scanning Electron Acoustic Microscopy (SEAM) is based on the detection of Electron Acoustic (EA) signals that are generated as a result of the interaction between a pulsed electron beam and the sample. SEAM enables ferro-electric domain mapping and mechanical stress profiling to be performed in relevant samples. This capability has the potential to significantly extend the range of applications on the SEM beyond what is presently available.

2. Advantages of SEAM

SEAM offers the following advantages over conventional SEMs as well as certain aspects of Scanning Acoustic Microscopes (SAMs):

Information derived from the thermal-acoustic signal generation mechanisms

Non-destructive imaging of sub-surface features with higher depths than conventional Secondary Electron (SE) and Back-Scattered Electron (BSE) electron imaging

A wide variety of information can be obtained based on the frequency, amplitude, phase and harmonic composition of the signal

Depth-resolved SEAM via frequency sweep and beam voltage change - 3D sub-surface tomography

Study of thermal-elastic related material properties, as well as the change of the properties with temperature

3. Illustrations of SEAM Applications

Ferroelectric domains in BaTiO₃

SE image SEAM image at 210 kHz

The SEAM image reveals the ferro-electric domain orientation in the bulk of the sample not possible with conventional SE imaging. This domain-mapping capability is a critical facility in the analysis of ferro-electric samples.

Stress profiling of Vickers Indentation in Al

SE image SEAM image at 76 kHz

The SEAM image shows the stress profile in the aluminium slab subjected to Vicker’s Indentation at 76 kHz. This capability allows extended sample stress-strain characterisation in mechanical testing applications.}