Hannover 2003 – wissenschaftliches Programm
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MS: Massenspektrometrie
MS 5: Massenspektrometr. Verfahren und Entwicklungen
MS 5.8: Vortrag
Donnerstag, 27. März 2003, 18:15–18:30, F 428
SSMS assessment of carbon contents in silicon single crystals — •Bernhard Wiedemann1, Joerg Dieter Meyer1, and Hans Christian Alt2 — 1Institute for Nuclear Physics, Johann Wolfgang Goethe-Universitaet, August-Euler-Str. 6 — 2FHM - Munich University of Applied Sciences, P.O. Box 200113
Residual carbon concentration in single crystalline silicon were investigated by use of a modernized spark source mass spectrometer, type 21−110, with ion-sensitive Q plate detection, photometric data acquisition and evaluation. The CPAA (by 12C(d,n)13N nuclear reaction) calibrated SSMS measurements of carbon concentrations are evaluated with a relative sensitivity coefficient of rsc = [C]ssms / [C]cpaa of 0.77 ± 0.04 (2σrsc) by use of the singly charged ions of the major isotope, 12C, and selected singly and multiply charged ions of the minor silicon isotopes, 29Si and 30Si. This SSMS method allows to measure quantitatively the carbon concentration in silicon above a detection limit of 5 ppb atomic. The reliability of measurements has been proven in the concentration range below 200 ppb atomic by the expected relationship between the carbon concentration [C]solid and the solidified fraction g during the Czochralski crystal growth along the axis of a silicon single crystal. A nonlinear regression of the Scheil equation [C]solid = k0 × [C]melt0 × (1 − g)k0−1 gives k0 × [C]melt0 = (31 ± 3) ppb atomic and 1 − k0 = 0.93 ± 0.05 for five samples and 0.04 ≤ g ≤ 0.85. Comparative measurements were also carried out by the FTIR method to investigate the conversion coefficient for the absorption coefficient of carbon, 12C, for the local vibrational mode absorption band at wavenumber 607.5 cm−1 (77 K).