The single crystal furnace is a device used in an inert gas environment (mainly nitrogen or helium) to melt polycrystalline materials using a graphite heater, employing the Bridgman method (direct pulling method) to grow single crystals without dislocations. It is capable of producing single crystals of materials such as semiconductors (silicon, germanium, gallium arsenide), metals (palladium, platinum, silver, gold), salts, and synthetic gemstones. Single crystals find primary applications in the semiconductor and solar industries.
In the Bridgman method, high-purity polycrystalline materials are heated in a crucible to a molten state. Subsequently, a rod with a seed crystal at its end is slowly lowered into the melt. Once the seed crystal and melt fuse, the seed crystal is slowly pulled upward in the appropriate thermal environment. The process involves subsequent steps such as crystal pulling, necking down, shoulder formation, rotation, diameter equalization, and finishing, completing the single crystal pulling operation.
A well-designed thermal field is crucial for growing high-quality single crystals, and the quality of the single crystal directly affects the yield in subsequent processes. The thermal field system primarily includes the crucible, guide tube, insulation tube, heater, etc., all made mainly of graphite. In the crystal pulling process, the high-temperature resistance, corrosion resistance, and strong thermal conductivity of graphite are essential characteristics.
The heater provides the heat source for material melting.
The crucible carries the inner quartz crucible. Due to its high carbon content, it possesses advantages such as strong thermal conductivity and corrosion resistance associated with carbon elements. Graphite crucibles come in various types, including circular, square, cylindrical, and irregular shapes, each applied in different fields and produced using different methods.
The insulation cylinder prevents internal heat from conducting outward, creating a thermal field space.
The guide tube prevents external heat from conducting to the inside, enhancing the growth rate of the crystal rod.
Applied in the crystal pulling, silicon industry, semiconductor, industrial furnaces, high-temperature furnaces, and pressure furnaces, currently in the single crystal furnace thermal field. Its features include a lower protective plate pressure pad and an upper cover, forming a structure with a bottom opening of a certain volume. The lower edge of the upper cover of the protective plate is fixedly connected to the upper surface of the lower protective plate, forming a cavity between the upper cover of the protective plate and the lower protective plate for placing insulating materials. This design maintains the original protective and insulating functions of the protective plate while providing bottom insulation, with a simple structure.
Graphite electrode support is used in the graphite thermal field of the single crystal furnace to stabilize the graphite electrodes and provide stable support. It includes the main support that connects the graphite electrode with a single point. The feature is that a support rod is installed below the graphite electrode, and the support rod is connected to the graphite electrode support through the upper graphite current matching block. The lower end of the support rod is equipped with a horizontal fine adjustment device to adjust the horizontal position of the graphite electrode to ensure normal production.
Generally used in the thermal field system of the single crystal furnace, where the quality of the thermal field has a significant impact on the quality of single crystal silicon. Each component in the thermal field plays a crucial role. The graphite electrode sleeve in the single crystal furnace thermal field system is generally located outside the graphite electrode. In simple terms, it is used to protect the graphite electrode, ensuring the normal operation of both the graphite electrode and the entire single crystal furnace thermal field system.
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