Abstract

A main chamber is provided through which a workpiece is loaded or unloaded. A second chamber is provided within the main chamber to cover the workpiece during evacuation and gas introduction processes performed within the main chamber. The second chamber protects the workpiece from floating dust deposited on parts within the main chamber and blown about by a turbulent flow of introduced or evacuated gas therein. The second chamber can be shaped like a bell jar and is made as small as possible. A driving circuit lifts the bell jar up and down. The gas pressure within the second chamber is maintained greater than or equal to that of the main chamber by a pressure control circuit to prevent dust intrusion into the second chamber. A slow leak circuit is provided as a pressure control device by forming a loose vacuum-seal between the second chamber and the main chamber. A gas introduction circuit and/or evacuation circuit may be connected to the second chamber. A workpiece transfer device is located at the outside of the second chamber. The second chamber may be part of a vacuum processing chamber, thereby allowing the workpiece to be directly loaded into and unloaded from the processing chamber.