Process and apparatus for controlling the melt level while pulling single crystals

US5437242A · kind A · utility

Assignee

• Wacker-Chemitronic Gesellschaft fur Elektronik Grundstoffe mbH · DE

Inventors

• Christian Hofstetter · Burghausen, DE
• Walter Berger · Erligheim, DE
• Werner Bauer · Neuötting, DE
• Bernd Mittelbach · Burghausen, DE

Key dates

• Filing date: Aug 18, 1993
• Grant date: Aug 1, 1995
• Expiry date: Aug 18, 2013

Classification

• Technology area (CPC Y): Emerging Cross-Sectional Technologies
• CPC primary: Y10T117/1068
• WIPO field: Measurement
• WIPO sector: Instruments

Abstract

A process and an apparatus for carrying out the process provides for the accurate and simple control of the melt level when pulling single crystals according to the Czochralski process. The process comprises disposing a mechanical reference mark above the melt in such a way that it causes a reflection from the melt surface. An image of the metal surface is then recorded, and with the aid of the recorded image the distance of the mechanical reference mark from the melt surface is determined. An actual signal proportional to this distance is then generated and is compared with a set point signal, and the melt level is changed as a function of any difference observed.