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Ultrasound Measurement of the Position of the Growing Interface During Directional Solidification of Silicon
M. Azizi, E. Meissner, J. Friedrich
Silicon (Si), Crystal Growth, Ultrasound Technique
Wafer-Based Silicon Solar Cells and Materials Technology
Subtopic: Silicon Feedstock, Crystallisation and Wafering
Event: 25th European Photovoltaic Solar Energy Conference and Exhibition / 5th World Conference on Photovoltaic Energy Conversion, 6-10 September 2010, Valencia, Spain
Session: 2CV.1.13
1520 - 1523
ISBN: 3-936338-26-4
Paper DOI: 10.4229/25thEUPVSEC2010-2CV.1.13
0,00 EUR
Document(s): paper


One of the most important parameters in crystal growth is the velocity of the moving solid/liquid interface. A common technique to detect the position of the solid/liquid interface is the sequential mechanical touching of the solidification front using a rod. The obvious disadvantage is that the solid/liquid interface can be disturbed during these measurements. Therefore, a sensor based on the ultrasound method was tested as a contactless, in-situ detection technique of the crystal growth interface. The setup consists of a standard ultrasonic transducer, which is positioned on top of a high temperature resistant ultrasonic waveguide. The waveguide itself is dipped into the silicon melt, in order to transfer the ultrasonic signal from the transducer through the melt. The signal can then be reflected either at the bottom of the crucible or at the solid/liquid interface. First measurements using this ultrasound diagnostic tool were performed. As a first prove the speed of sound in liquid silicon was measured. The obtained value corresponds well to published data. In a second experiment the growth rate was determined in/situ during directional solidification of multicrystalline silicon. The measured growth rate correlates well with the value obtained from mechanical touching of the interface. The deviations of the growth rate obtained by these two methods will be discussed.