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Keywords:

  • silicon;
  • optical furnace;
  • ribbon;
  • thin foils

Abstract

It is well known that impurity contamination is a very important factor in silicon processing. Contamination arises from crucibles or graphite susceptors during crystal growth, from the use of fibers or dies as in the case of String ribbon or EFG technologies respectively. Furthermore, every hot part in a crystal growth system will contribute to increase impurity contamination. Optical processing using halogen lamps provides clean method, with available fast rise and fall ramps, cold wall furnaces, with great flexibility in many situations related to materials processing and in particular in photovoltaics. Optical power provided by halogen lamps is very cheap, which is an important aspect for an industry that needs to reduce process costs. Techniques based in lamp power radiation have been in use in our laboratory at the University of Lisbon for many years. Several examples of the use of such optical techniques are presented, illustrating its application to silicon ribbon growth, kerfless techniques and on its successful application for photovoltaics in a gas-to-wafer path, bypassing both the Siemens and the traditional wafering steps. (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)