Polycrystalline silicon microwave drying equipment, widely used for semiconductor polysilicon drying.

Polysilicon is a form of elemental silicon. When the molten elemental silicon solidifies under supercooling conditions, the silicon atoms are arranged in a diamond lattice shape into many crystal nuclei. If these crystal nuclei grow into crystal grains with different crystal orientations, these crystal grains combine to crystallize into polysilicon. . Utilization value: From the current development of international solar cells, it can be seen that the development trend is monocrystalline silicon, polycrystalline silicon, ribbon silicon, thin film materials (including microcrystalline silicon-based thin films, compound-based thin films, and dye thin films).

1. Grease: In the production process of polysilicon, the damage of oil molecules to polysilicon is very serious. It has been proved that a few ppm of oil content in the entire process system may cause the polysilicon reaction rate to slow down, the yield to decrease, and even the silicon reaction to stop. Therefore, the degreasing process of polysilicon devices is particularly important.

2. water: The water contains a lot of chloride ions, chloride ions are very sensitive to the reaction of polysilicon. Equipment and system drying processes are critical.

3. Chloride ion residues: Residual chlorine ions on the surface of water and other solutions have a great influence on polysilicon. Therefore, it is very important to rinse the equipment with pure water after cleaning.

4. Oxides, dust and other impurities: The presence of other dirt has a great influence on the production of polysilicon. Therefore, in the process of equipment cleaning, it is necessary to use pickling process to clean other dirt.

In polysilicon processing production, the most critical is to use pure water for cleaning and drying. Microwave equipment can precisely meet the requirements, heating speed, dehydration fast. The efficiency can be increased by several dozen times of electric heating and no secondary pollution, and the purity of polysilicon can be guaranteed, which is beneficial to the quality assurance of subsequent processing. In order to meet the high-temperature drying of polysilicon, the microwave drying equipment uses a material that is resistant to high temperature of 1000 degrees to ensure the smooth completion of drying.

     The overall shape of microwave drying equipment is compact, beautiful, smooth, and has a small footprint. For the physical properties of the material, a reasonable box size is designed so that the microwave power density in the heater is uniform, and the microwave is fed in from the top down to make the material heating more uniform. Adopt new microwave drying technology and equipment. It can realize the pollution-free and uniform drying of materials, and at the same time can greatly reduce the drying temperature. In addition, the drying speed is usually increased by several times or more, the production efficiency is greatly improved, the drying energy consumption is usually reduced by more than 50%, and finally, safe and efficient production is achieved.

The characteristics and mechanism of microwave drying are different from those of ordinary drying techniques. In summary, they have the following characteristics:

1) The dry layer in the microwave drying process is first formed inside the material and then spread outward from the inner layer. The reason is that the material is heated at the same time inside and outside under microwave conditions. The internal temperature is higher than the outside. The water vapor is discharged from the inner surface layer and the inside of the material forms a dry layer. The conventional heating is easy to form a dry hard shell on the outside of the material. This will not only affect the material. The quality and appearance will also reduce the drying speed. Microwave drying fundamentally avoids the above situation.

2) Microwave drying and energy saving. The use of far-infrared and steam energy for drying, the energy efficiency of less than 50%, while the use of microwave energy as a result of energy utilization of up to 75%, than the far infrared and steam drying energy consumption decreased by more than 25%.