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AssigneeWacker-Chemitronic Gesellschaft fur Elektronik-Grundstoffe mbH
InventorWerner Zulehner
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In the crucible pulling of silicon according to the Czochralski technique, ilicon monoxide forms as a result of the silicon melt reacting with the quartz crucible containing the melt, and evaporates and deposits in the form of solid particles on the upper edge of the crucible, on the monocrystalline rod, on the walls of the vessel, and also on recharging devices in the upper pulling chamber. These solid particles can fall back into the melt and then cause dislocations and polycrystalline growth in the growing silicon rod. As a result of the reaction of the carbon of the hot graphite parts with silicon monoxide, carbon monoxide is also formed and this partially diffuses into the melt and gives rise to carbon impurities in the silicon rod. In addition, because of heat irradiation from the inner wall of the quartz crucible as it becomes more empty, high pulling speeds, such as those usual in crucible-free zone pulling, cannot be obtained. These disadvantages of the conventional crucible-pulling process are effectively obviated according to the invention by a pot-like device which entails a partial covering of the melt surface, the crucible and the space laterally adjoining the crucible.
In a process for the crucible pulling of crystalline semiconductor rods according to the Czochralski technique wherein crystalline semiconductor rods are pulled from a melt in a crucible, the improvement comprising:
A crucible and cover assembly for effecting the partial covering of a crucible and a semiconductor melt contained in the crucible during the pulling of crystalling crystalline semiconductor rods in accordance with the Czochralski crucible-pulling technique, comprising:
Dependencies are inferred from the claim text.