As verification manner of contact state of the ultrasonic sensor, the ultrasonic sensor which at least monitors the plasma abnormal discharge 3 in the plasma abnormal discharge monitor, and

摘要

PROBLEM TO BE SOLVED: To improve a reliability and secure an abnormal discharge detection accuracy in relation with the confirmation of the contact state of the ultrasonic sensor by uniformly mounting an AE sensor and watching the change of the mounting state with the passage of time.;SOLUTION: At least three ultrasonic sensors 1-3 are mounted to the plasma treatment device out of which, the ultrasonic sensor 1 is used for wave transmission, and the ultrasonic sensors 2, 3 are used for wave reception. The ultrasonic signal transmitted from the ultrasonic sensor 1 is received by the ultrasonic sensors 2, 3, and the contact state of respective ultrasonic sensors 1-3 are confirmed by successively switching the function of those sensors from transmission use to receiving use.;COPYRIGHT: (C)2003,JPO