Process for control of the melt level during single crystal pulling

摘要

The invention relates to a process and a device for carrying this out by which precise and simple control of the melt level can be achieved during pulling of single crystals by the Czochralski method. The process comprises that a mechanical reference marker is mounted above the melt in such a way that a reflection is caused on the melt surface. An image of the melt surface is then recorded and with the aid of the recorded image the distance of the mechanical reference marker to the melt surface is determined. An actual value signal proportional to this distance is then generated, compared with a preset signal, and the melt height is changed in relation to a determined difference.