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Experimental verification of the numerical model for a CaF2 crystal growth process

: Molchanov, A.; Hilburger, U.; Friedrich, J.; Finkbeiner, M.; Wehrhan, G.; Müller, G.


Crystal research and technology 37 (2002), Nr.1, S.77-82
ISSN: 0023-4753
ISSN: 0232-1300
Fraunhofer IIS B ( IISB) ()
numerical model; single crystal; crystal growth process; numerical simulation; internal heat transfer; semitransparent crystal; numerical modeling; IC-lithography; radiative heat transport; software package; internal heat transport; in-situ measurement system; temperature distribution

Large calcium fluoride (CaF/sub 2/) single crystals are required for the fabrication of lenses in the so-called wafer-steppers of future IC- lithography technologies operating at 193 nm and 157 nm. Numerical simulation plays an important role in designing an adequate growth set- up and processing conditions for the growth of high quality crystals. An important issue is the consideration of the internal heat transfer by radiation in the semitransparent CaF/sub 2/ during the crystal growth process. Results of the numerical modeling of the heat transport are presented, which are obtained by using the software package CrysVUn++ with different models considering the internal heat transport in CaF/sub 2/. To improve the availability of experimental data on CaF/sub 2/ bulk growth, an especially designed R&D facility was built. This growth system is equipped with a variety of in-situ measurement systems to detect the temperature distributions in the crystal and melt region. Calculated temperature distributions are compared with experimental data. Also the first results on single crystal growth are reported.