Method for measuring the diameter of a semiconductor rod produced by means of zone melting

摘要

In order to automate the floating zone melting of semiconductor material, the diameter of the monocrystalline semiconductor rod extracted from the melting zone must be measured continuously. It is known to use the means of television engineering for this purpose. The present invention is intended to specify a method by means of which the diameter can be measured reliably and accurately. Starting from the finding that the rod growing out is brighter at the solid/liquid boundary than is the melt, the video signals from the television images of the melt region are tested as to whether their amplitude over a plurality of adjacent rows extending perpendicular to the rod axis is smaller than a threshold value decreasing from image to image. If this condition is satisfied, the diameter of the rod in the bright row adjacent to the dark rows is determined by measuring the duration of the white signal given a threshold value diminished by a prescribed amount. The invention is applied in floating zone melting. <IMAGE>