| 摘要 |
PROBLEM TO BE SOLVED: To provide a vacuum device of simple structure capable of eliminating a pressure distribution close to the stage in a chamber. SOLUTION: An exhaust port 14 is formed at the respective corners of the bottom face of a chamber 10, and a pressure gage 16 is provided close to the respective exhaust ports 14. The respective exhaust ports 14 are communicated with a branch pipeline 17 through a variable-conductance valve 19 (hereinafter called as valve), and a turbo molecular pump 15 is connected to the tip of the branch pipeline 17. The signal corresponding to the pressure from each pressure gage 16 is compared with the target of each pressure gage 16 in a control part and outputted as a control signal corresponding to difference from the target to a valve driving motor, the valve 19 is opened or closed based on the control signal, hence the amt. of air discharged from the exhaust ports 14 is corrected, and the pressure distribution close to the stage in the chamber 10 is eliminated.
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