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Sheet resistance imaging (SRI) - A contactless and spatially resolved method for the determination of doping inhomogeneities

: Isenberg, J.; Schubert, M.C.; Biro, D.; Froitzheim, A.; Warta, W.

Volltext urn:nbn:de:0011-n-501904 (333 KByte PDF)
MD5 Fingerprint: 54e1549edb11335b687f2f6185b2e145
Erstellt am: 13.10.2012

20th European Photovoltaic Solar Energy Conference 2005. Proceedings : Barcelona, 6-10 June 2005
München: WIP-Renewable Energies, 2005
ISBN: 3-936338-19-1
European Photovoltaic Solar Energy Conference <20, 2005, Barcelona>
Konferenzbeitrag, Elektronische Publikation
Fraunhofer ISE ()

Sheet Resistance Imaging (SRI) is an optical method for the investigation of doping concentrations and inhomogeneities. The measurement principle is based on the interaction of free carriers in silicon and radiation in the mid-IR. By using a camera sensitive in the infrared SRI is the first measurement technique for emitter doping that realizes spatial resolutions of some 100 ?m on all common wafer sizes with measurement times of a few seconds only. As SRI is a contactless and purely optical method, the principle restrictions in spatial resolution of four-point probing are overcome. The most obvious application is the investigation of inhomogeneities in standard emitter diffusion. Thanks to the very high spatial resolution achievable (below 50 ?m), SRI is very well suited to the detailed study of selective emitter structures. Additionally, an example of SRI measurements on high low junctions (e. g. back surface fields) is discussed. As SRI is a purely optical measurement technique inhomogeneities in roughness of the sample surface are of utmost importance and may lead to erroneous results. Possibilities for avoiding and suppressing such effects are discussed and significant progress towards the application of SRI on alkaline etched multicrystalline silicon samples is demonstrated.