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Quantitative Measurement of Dopants (sub-ppba), Oxygen, and Carbon (sub-ppma), and Metals (sub-ppma) in PV Si Feedstock and Wafers by SIMS
L. Wang, R.S. Hockett
Qualification and Testing, Silicon (Si), Impurities, SIMS
Wafer-Based Silicon Solar Cells and Materials Technology
Subtopic: Silicon Feedstock, Crystallisation and Wafering
Event: 23rd European Photovoltaic Solar Energy Conference and Exhibition, 1-5 September 2008, Valencia, Spain
Session: 2CV.3.3
1209 - 1212
ISBN: 3-936338-24-8
Paper DOI: 10.4229/23rdEUPVSEC2008-2CV.3.3
0,00 EUR
Document(s): paper


Secondary Ion Mass Spectrometry (SIMS) can be used to quantitatively measure bulk dopants, oxygen and carbon, and metals at exceptionally low levels in both crystalline and polycrystalline Si for PV. The approach is to use CAMECA magnetic sector SIMS instruments and protocols which are optimized for these bulk measurements. Accuracy is traceable to NIST SRMs for B, P, and As, and ion implanted reference standards for other elements. Traditional analytical methods have their strengths but also their limitations. For dopants, resistivity is affected by compensation of other dopants, and low temperature FTIR and PL require the growth of a single crystal ingot slug. For oxygen and carbon, FTIR is limited to interstitial oxygen and substitutional carbon in single crystal Si. SIMS and Glow Discharge Mass Spectrometry (GDMS) overcome these limitations, but SIMS has lower detection limits and better precisions which may be needed in some cases.