PLASMA PROCESSING APPARATUS

A plasma processing apparatus capable of detecting sealing abnormality of each gate is disclosed. This apparatus includes an outer chamber constituting a vacuum vessel, an inner chamber disposed within the outer chamber for permitting a plasma to be formed in a vacuumed processing chamber as internally provided therein, a workpiece table below the processing chamber for holding thereon a wafer to be processed, a first gate valve disposed in a sidewall of the inner chamber for driving a gate to open and close while the wafer is transferred therethrough, and a second gate valve disposed in a sidewall of the outer chamber for opening and closing a gate while the wafer is transferred therethrough. After the wafer is put on the table, a pressure variation of an intermediate room formed between the inner and outer chambers sealed by the gate valves closed, thereby detecting a decrease in sealing performance.