Device for protecting an electrode seal in a reactor for the deposition of polycrystalline silicon
A reactor, polysilicon technology, used in chemical methods, circuits, discharge tubes, etc. to react gases with non-granular solids, and can solve problems such as failure to reach final diameter, system output decline, ground faults, etc.
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[0069] Figure 3a A second preferred embodiment is shown.
[0070] Here, at least one cover 6 is provided, which contacts the electrode holder 1 and the base plate 3 .
[0071] The cover 6 surrounds the sealing body 2 by radially surrounding it.
[0072] The cover 6 must consist of an electrically insulating material with very good thermal conductivity. Silicification of the cap 6 is therefore not possible.
[0073] For this purpose, silicon nitride and aluminum nitride can be used, or have a high thermal conductivity of greater than 10 W / mK at room temperature, preferably greater than 50 W / mK, particularly preferably greater than 150 W / mK and have a temperature of greater than 10 W / mK at room temperature. 9 Ωcm, preferably greater than 10 11 Other ceramic materials with a resistivity of Ωcm.
[0074] In order to increase the heat dissipation of the cover 6, the cover 6 may preferably be firmly connected with the cooled electrode holder 1, for example, connected by thread...
Embodiment 1
[0151] Example 1 (according to the first preferred embodiment)
[0152] A mantle of ultrapure graphite was placed on the electrode holder. In order to protect the sealing body, a translucent quartz ring is placed around the electrode holder at a distance of 10 mm. The size of the cover disk is such that it protects the electrode holder and at least the area of the floor with the quartz ring on it. Due to the high gas space temperature, the quartz ring and the mantle are silicided by the thin silicon layer during deposition. The size of the surrounding gap between the mantle and the quartz ring is such that spark breakdown does not occur from the mantle to the quartz ring under the applied voltage.
[0153] Out of 100 lots, 5 lots failed due to ground fault. Individual silicon fragments reach the electrode holder through the surrounding gap, causing a ground fault between the electrode holder and the base plate.
[0154] Due to the additional protection of the cover plate...
Embodiment 2
[0155] Example 2 (according to the second preferred embodiment)
[0156] The electrode holder and the sealing body are protected by applying a cover made of aluminum nitride. In this embodiment, the cover is in contact with the electrode holder above and with the cylindrical portion of the electrode holder, and reaches the bottom plate. Due to the high thermal conductivity of 180 W / mK (at room temperature), as well as the heat dissipation of the heat absorbed by the reaction gas and the heat conduction through the cooled contact surface, the surface temperature is so low that silicide does not occur on the cover surface. Furthermore, the material of the cover is an electrically insulating material. Due to the complete encapsulation of the seal, ground faults caused by silicon fragments cannot occur. Therefore, 100 batches have a ground fault rate of 0%. Due to the lower cover temperature, the service life of the seal is increased to 9 months.
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