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Crystal Growth Process

IP.com Disclosure Number: IPCOM000078536D
Original Publication Date: 1973-Jan-01
Included in the Prior Art Database: 2005-Feb-26
Document File: 2 page(s) / 51K

Publishing Venue

IBM

Related People

Hull, EM: AUTHOR

Abstract

During the production of semiconductor III-V materials, it is desirable to avoid movement of the growing crystal material while moving the solid-liquid interface during a gradient freeze process.

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Crystal Growth Process

During the production of semiconductor III-V materials, it is desirable to avoid movement of the growing crystal material while moving the solid-liquid interface during a gradient freeze process.

These objects are accomplished by providing an apparatus wherein a steep thermal gradient is caused to move down the axis of molten crystal forming material, causing directional freezing of the molten charge.

The furnace is constructed of a highly recrystallized alumina tube, on which is wound a closely spaced helix of platinum based alloy resistance wire 1. The windings or turns of this helix, in the region of the furnace where the boat 2 resides, are tapped on each successive adjacent winding by a conductor which is led out radially to an externally accessible terminal post 3. The tube and resistance windings are enclosed in a thermally and electrically insulating medium, sufficient to allow the furnace to reach a temperature above the melting temperature of the crystal to be grown.

In use, the externally accessible posts 3 which are attached to successive adjacent windings are connected to the programming device 4, which functions to shunt a portion of the furnace power from individual turns of the heater winding, thereby varying the temperature of individual windings and, therefore, localized regions of the furnace. This variation in the temperature of localized regions of the furnace is accomplished in such a way, that the result is the gradua...