Controlling the axial temperature gradient in inductively heated Czochralski systems

Abstract

A heating system is described that allows to increase the temperature gradients in rf-heated Czochralski setups during the growth. This system applies an active afterheater, operated by a separate induction coil parallel to that heating the crucible. By changing the inductivity of an additional coil located outside the growth chamber, the ratio of the rf currents flowing through the crucible and afterheater and, consequently, the geometry of the heat input to the setup can be altered. The efficiency of the heating systems has been demonstrated in various experiments.

Numerical Study of Heat Transport and Fluid Flow of Melt and Gas during the Seeding Process of Sapphire Czochralski Crystal Growth

“…This type of temperature variation is suitable for the most grown crystals such as sapphire because they are sensitive to thermal stress, cracks, defects, and dislocations. By using this kind of temperature profile along the symmetry axis, control of thermal stress in the grown crystal is possible 9 Vertical temperature profiles along the axis of symmetry taken from the crucible bottom to the afterheater hole for (a) configuration without a gap and (b) configuration with a gap between crucible and afterheater.…”

“…By using this kind of temperature profile along the symmetry axis, control of thermal stress in the grown crystal is possible. 20 Figure 10 represents the temperature variation at the meltgas interface for both configurations. It shows that the temperature variation along the melt surface is about linear with the rate δT h ∼ 3 °C/mm except in the crucible meniscus as well as close to the symmetry axis.…”

Model experiments for Czochralski crystal growth processes using inductive and resistive heating

“…A series of experiments is performed to investigate the thermal and electromagnetic behavior of both heaters (cf. [3,5]), to get input data for validation of numerical simulations, as well as to analyze the advantages and disadvantages of both heating concepts applied in a similar setup.…”

“…Both induction heating [3,4] and graphite resistance heaters [5,6] are applied in the CZ growth technique, selected based on various requirements such as cost efficiency, electromagnetic forces, or degree of purity inside the furnace. Numerical simulations have been applied for investigation of both concepts [4,6].…”

Effect of New Thermal Insulation to the Growth of LiNbO₃ Single Crystal by Czochralski Method

“…The Czochralski method with RF induction heating is probably the most widely used technique for the growth of high melting point oxide single crystals, in a scale that allows for commercial application [4]. For a given material the process first described by Czochralski [5] is the fastest melt growth method and is therefore almost always the method which produces crystals most rapidly so that less contamination occurs.…”