A new approach to the CZ crystal growth weighing control

• Published in: Journal of crystal growth Vol. 390; pp. 67 - 70
• Main Authors: Kasimkin, P.V., Moskovskih, V.A., Vasiliev, Y.V., Shlegel, V.N., Yuferev, V.S., Vasiliev, M.G., Zhdankov, V.N.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.03.2014
• Subjects: A1. Control system design; A2. Automated melt growth; A2. Czochralski method; B2. Semiconducting germanium; Control systems; Crystal growth; Dynamical systems; Hydrostatic pressure; Instability; Semiconductors; Stability; Weighing; A1. Control system design; B2. Semiconducting germanium; A2. Czochralski method; A2. Automated melt growth
• ISSN: 0022-0248; 1873-5002
• DOI: 10.1016/j.jcrysgro.2013.12.027

The aim of a new approach was to improve the robustness of the weighing control of CZ growth especially for semiconductors, for which the “anomalous“ behavior of the apparent weight provokes instability of the servo-loop. In the described method, the periodic reciprocating measuring motion of small amplitude is superposed on the uniform pull-rod movement. The cross-sectional area is determined from the weight sensor responses that are modulated mainly by the forces of hydrostatic pressure. By the example of germanium crystal growth, it is shown that in the control system, based on such a way of the diameter measuring, a simple PI control law provides a good close loop system's stability and dynamics for the materials with the “anomalous” behavior of a weighing signal. The effect of a meniscus on the modulation measuring of a crystal diameter is also discussed. •Reciprocal motion of pull rod is used for measuring crystal diameter in CZ growth.•Modulation way of diameter measuring hugely improves weight control system dynamics.•Ge crystals are grown with PI control law using a new method of diameter measuring.