| 摘要 |
PROBLEM TO BE SOLVED: To prevent adherence of deposits, and deposition of a large volume of deposits by providing at least a substantially thin-walled upper end portion of a cylindrical upper part to store an evaporating material which is projected above a base part to be cooled of a hearth with the evaporating material stored therein in a vacuum chamber. SOLUTION: A hearth 41 comprises a box-shaped base part 41b of container shape in which a refrigerant is circulated, and an upper part 41a to stored columnar pellet-like evaporating material to be fed on a batch basis. Preferably, the wall thickness (t) of at least an upper end portion 41c of the upper part 41a is >=1 mm to <=5 mm, the angleθ1 of an outer wall surface 41e is >=0 deg. to <=20 deg., and the angleθ2 of an inner surface 41d of the upper end portion 41c is >=0 deg. to <=45 deg.. Since most of the upper part 41a is constantly located within the irradiation range of a plasma beam 300, deposits 200' to adversely affect the beam irradiation are re-evaporated and hardly deposited.
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