Method for cleaning bell jar, method for producing polycrystalline silicon, and apparatus for drying bell jar

摘要

A bell jar includes a metallic bell jar (1), and a metallic base plate (2) on which the bell jar (1) is placed, and packing (3) seals an inside of a container. To the base plate (2), a pressure gauge (4), a gas introduction line (5), and a gas discharge line (6) are connected so as to allow monitoring of internal pressure of the bell jar (1) and introduction and discharge of a gas. A vacuum pump (7) is provided in a path of the gas discharge line (6), and the vacuum pump (7) reduces internal pressure of the bell jar so as to be lower than vapor pressure of water. The vacuum pump (7) reduces the internal pressure of the bell jar so as to be lower than vapor pressure of water, thereby efficiently removing moisture, and completing drying of the bell jar in a short time.

主权项

1. A method for producing polycrystalline silicon, said method comprising:
repeating a plurality of times a precipitation of polycrystalline silicon by the Siemens method in a bell jar, wherein after completion of precipitation of a batch of polycrystalline silicon and before a precipitation of a next batch of polycrystalline silicon, cleaning said bell jar by the following method of cleaning a bell jar: washing said bell jar by contacting water with an inside of said bell jar; and then drying said bell jar by reducing a pressure inside of said bell jar to a pressure of 1000 Pa or less to remove moisture, using a vacuum pump capable of achieving 200 Pa or less; and then introducing a high purity inert gas having a dew point of −40° C. or less into said bell jar to return the pressure inside of said bell jar to atmospheric pressure, wherein a time from completion of the washing to completion of the drying is 1.2 hours or less, to obtain polycrystalline silicon having an electric resistivity of 1500 Ω·cm or more.