Application Of Graphite In Polysilicon Ingot Furnace

In polysilicon ingot furnace, graphite material is required for multiple components. In particular, the heating materials and thermal insulation materials used in heaters are important supporting materials at present. Therefore, the development of high-purity graphite materials promotes the further development of polycrystalline silicon ingot production process.

1. Heating Materials Used In Heaters

In the design of polycrystalline silicon ingot furnace, in order to melt silicon, appropriate heating mode must be adopted. In terms of heating effect, induction heating and radiation heating can reach the required temperature. Generally, radiation heating is used, which can accurately control the heat transfer in the crystallization process, and is easy to form a vertical temperature gradient in the disaster.

Therefore, the heating capacity of the heater must exceed 1650 ℃. At the same time, the material of the heater cannot react with the silicon material, does not pollute the silicon material, and can be used for a long time in vacuum and inert atmosphere. Suitable heaters include tungsten, molybdenum and non-metallic graphite. Because tungsten and molybdenum are expensive and difficult to process, graphite comes from a wide range of sources and can be processed into various shapes.

In addition, graphite has the characteristics of small thermal inertia, rapid heating, high temperature resistance, good heat shock resistance, large radiation area, high heating efficiency and stable basic performance. Therefore, high-purity graphite can be widely used as a good heater material.

2. Thermal Insulation Materials Used In Heaters

For the ingot casting process, in order to improve the production efficiency, the heating speed of the equipment is required to be as fast as possible; Due to the use of vacuum process, the amount of gas discharged from the materials in the furnace shall be as small as possible to shorten the vacuum exhaust time; At the same time, the formation of temperature gradient in silicon material also needs the accurate improvement of thermal insulation layer. The quality of thermal insulation layer should be as light as possible to reduce the inertia during lifting and affecting the control accuracy.

To sum up, the selection requirements for thermal insulation materials are: high temperature resistance, low density, small thermal conductivity, less heat storage, good thermal insulation effect, less air release, light weight and small expansion coefficient. Among many fire-resistant and thermal insulation materials, high-purity graphite is the most ideal.

Graphite material plays an irreplaceable role in the production of polycrystalline silicon ingot. Its excellent characteristics provide a guarantee for maintaining a high temperature field and excellent heat insulation effect in the ingot furnace. Therefore, the future development of graphite material can further promote the optimization and transformation of polycrystalline silicon ingot furnace and contribute to the reduction of polycrystalline silicon ingot production cost.