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tungsten heaterIn large CVD(Chemical Vapor Deposition) system (diameter of the reaction chamber is longer than50cm), in order to form a large area and uniform film, using a large area and fence Czochralski tungsten wire to eliminate the uneven temperature and deformation problem of heating wire. But during film growth, large-scale CVD system usually have greater power and gas consumption, and when the arrangement of Czochralski tungsten wire, total current through the hot wire will be great, generally at 100 amperes or more. Therefore, it needs high current and high power hot wire heating transformer and a corresponding device for cooling systems. The device is relatively complex, which is not suitable for doing research for an experimental basis.

For the core heating section of tungsten heater, it can be improved by the following measures to solve the above problems.
1. Tungsten wire can be wounded into a flat ring, and it would be molded in a one time with a special material mold.
2. Using the high temperature boron nitride ceramic rod whose melting point is higher than 2400 ℃ to be fixed with tungsten wire.
3. Put and fix the boron nitride ceramic rod on the upper end of the electrode, so that the whole heating tungsten wire can keep parallel with the substrate surface.
4. Before using the new tungsten wire, it should be through the stress treatment.
After the new tungsten has being wounded and fixed, in an normal growth atmosphere, dong the annealing process for a long time at low temperatures to eliminate stress generated in the process of wound and stereotype.

The heating process is: every time the temperature of tungsten wire rises 100 ℃, then heating for 2 hours, until the temperature of tungsten wire reaches the growth temperature.

This is a specific improvement measures for the tungsten wire wound, this kind of tungsten heater device will greatly improve the efficiency of the subsequent coating.

 

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