Single crystal furnace shutdown thermal field damage prevention method

Abstract

The invention provides a single crystal furnace shutdown thermal field damage prevention method which comprises the following steps of: 1, drawing a crystal when residual molten silicon liquid existsin a quartz crucible, and enabling the first length of the crystal to enter a water-cooling heat shield; 2, after the crystal is drawn to a second length, stopping drawing the crystal, and enabling one end of the crystal to be in contact with the liquid level of the molten silicon liquid; 3, after the crystal is static, reducing the heating power of an auxiliary heater at the bottom of the singlecrystal furnace to zero; 4, reducing the power of the main heaters around the single crystal furnace in three stages until the heating power of the main heaters is reduced to zero; and 5, cooling fora certain period of time, and disassembling the single crystal furnace. According to the method, a single crystal with a certain length can be drawn to increase the heat transfer volume, accelerate the condensation speed of molten silicon liquid in the middle of a quartz crucible and reduce the stress concentration ratio, a heater on the single crystal furnace stops heating in a stepped mode, thecondensation speed of silicon around the quartz crucible is reduced, a stress release area is reserved, and therefore the integrity of a thermal field is guaranteed to the maximum extent.

Description

technical field [0001] The invention mainly relates to the technical field of crystal material processing equipment, and in particular to a method for stopping a single crystal furnace to prevent thermal field damage. Background technique [0002] During unconventional shutdown, liquid silicon will expand in volume during solidification and cooling, and the crystallization sequence of liquid silicon is that the liquid surface first forms a crystallization surface, and the crystallization surface will extend downward as the temperature decreases, but close to the middle and bottom of the liquid silicon Since the upper part crystallizes to form an insulating layer, the liquid silicon at the middle bottom and the upper crystallization surface form a large temperature gradient. This change will form stress that is difficult to release from the upper part under the inverse ratio curve of temperature and time. [0003] The volume change of liquid silicon will look for weak points ...

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Problems solved by technology

[0002] During unconventional shutdown, liquid silicon will expand in volume during solidification and cooling, and the crystallization sequence of liquid silicon is that the liquid surface first forms a crystallization surface, and the crystallization surface will extend downward as the temperature decreases, but close to the middle and bottom of the liquid silicon Since the upper crystallization forms an insulating layer, the liquid silicon at the middle bottom and the upper crystallization surface form a large temperature gradient. This change will form a stress that is difficult to release from the upper part under the inverse ratio curve of temperature and time.

[0003] The volume change of liquid silicon will look for weak points around the quartz crucible, but this volume change is often restricted by the quartz crucible and the crucible state supporting the quartz crucible and cannot proceed freely, so internal stress is generated, and the stress changes with the outside world. Slow contact at normal temperature reaches the highest level, making the container and supporting container unable to withstand damage

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