Patent ID: 6897161

Claim:
A method of cleaning an electrode plate used in a plasma processing apparatus, the electrode plate having a plurality of gas nozzles through which a process gas is supplied to a processing zone of the plasma processing apparatus, the gas nozzles passing through an entire thickness of the electrode plate, the method comprising: immersing the electrode plate in an cleaning agent; and removing deposited layers on inner walls of the gas nozzles formed when the electrode plate is used in the plasma processing apparatus, the removing including radiating ultrasonic waves toward a surface of the electrode plate having openings of the plurality of gas nozzles from an ultrasonic wave radiation surface of a horn connected to an ultrasonic vibrator, a power density of the ultrasonic waves defined by a ratio of an electric power input to the ultrasonic vibrator to an area of the ultrasonic wave radiation surface being not lower than 5 W/cm 2 , wherein a square of a wavelength of the ultrasonic wave in the cleaning agent is larger than the area of the radiation surface.