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HCl gas gettering of low-cost silicon

: Hampel, J.; Ehrenreich, P.; Wiehl, N.; Kratz, J.V.; Reber, S.


Physica status solidi. A 210 (2013), Nr.4, S.767-770
ISSN: 0031-8965
ISSN: 1862-6300
ISSN: 1521-396X
ISSN: 1862-6319
Fraunhofer ISE ()
Materialien - Solarzellen und Technologie; Silicium-Photovoltaik; kristalline Silicium-Dünnschichtsolarzelle; HCI etching; UMG; 3D transition metals

HCl gas gettering is a cheap and simple technique to reduce transition metal concentrations in silicon. It is attractive especially for low-cost silicon materials like upgraded metallurgical grade (UMG) silicon, which usually contain 3d transition metals in high concentrations. Etching of silicon by HCl gas occurs during HCl gas gettering above a certain onset temperature. The etching rate as well as the gettering efficiency was experimentally determined as a function of the gettering temperature, using UMG silicon wafers. The activation energy of the etching reaction by HCl gas was calculated from the obtained data. The gettering efficiency was determined by analyzing Ni as a representative of the 3d transition metals in the wafers with and without applied HCl gas gettering. The Ni concentrations were measured by inductively coupled plasma mass spectrometry (ICP-MS).