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An Investigation of the Limit of Detection and the Scattering Dependence of the Optical Precipitate Profiler (OPP)

Published online by Cambridge University Press:  10 February 2011

L. Mule'stagno
Affiliation:
MEMC Electronic Materials Inc., 501 Pearl Dr., St. Peters, MO 63376, USA
D.E. Hill
Affiliation:
MEMC Electronic Materials Inc., 501 Pearl Dr., St. Peters, MO 63376, USA
R. Standley
Affiliation:
MEMC Electronic Materials Inc., 501 Pearl Dr., St. Peters, MO 63376, USA
M. Olmo
Affiliation:
MEMC Electronic Materials Spa., Viale Gherzi 8, Novara, Italy
J.C. Holzer
Affiliation:
MEMC Electronic Materials Inc., 501 Pearl Dr., St. Peters, MO 63376, USA
R. Falster
Affiliation:
MEMC Electronic Materials Spa., Viale Gherzi 8, Novara, Italy
P. Fraundorf
Affiliation:
University of Missouri- St. Louis, Physics Dept., 8001 Natural Bridge, St. Louis, MO 63121, USA
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Abstract

The Optical Precipitate Profiler (OPP) and similar instruments are establishing themselves as routine techniques for measuring bulk micro-defect density (BMD) and denuded zone depths in semiconductor wafers. This task has traditionally been done by means of the cleave-and-etch technique in which defects are counted on a cleaved edge of an etched wafer using an optical microscope. The OPP makes this task faster, simpler and more accurate. In addition it can perform the measurement on a whole wafer.

We have used the OPP to measure defect density and scattering intensities from a set of silicon wafers with different precipitate sizes. The wafers were all given the same nucleation heat treatment but the precipitates were then grown at 1000°C for 1, 2, 4, 8, 16 and 32 hours. The size distributions and densities of the precipitates in each wafer were determined by Transmission Electron Microscopy (TEM). In a second experiment wafers with precipitate densities varying over four orders of magnitude as determined by cleaveand-etch were also measured by the OPP.

From these experiments we have estimated that the OPP can detect defects with an equivalent radius of 16 ± 8 nm and larger. We have also found that the scattering voltage (strength) depends on the precipitate radius, r3, as approximately r3 and that there is an upper number density limit above which the OPP is unable to measure the precipitate density accurately. For our setup this upper density limit was about 1.5 - 2.0 × 1010 defects/cm3 as measured by cleave-and-etch.

Type
Research Article
Copyright
Copyright © Materials Research Society 1998

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