Patent ID: 7223446

Claim:
A method comprising: performing a plasma CVD to form a film on a surface of an object in a reaction chamber of a plasma CVD apparatus, wherein said plasma CVD apparatus comprises: a high frequency power supply; a first electrode and a second electrode in the reaction chamber; a matching circuit between the high frequency power supply and the first electrode and between the high frequency power supply and the second electrode; a first change-over switch between the high frequency power supply and the first electrode and between the high frequency power supply and the second electrode; a pulse amplitude modulation circuit between the high frequency power supply and the first electrode and between the high frequency power supply and the second electrode; an inverter circuit between the first change-over switch and the second electrode; a second change-over switch between the first change-over switch and the second electrode; and a wiring line for ground between the first change-over switch and the second electrode; after performing the plasma CVD, cleaning an inside of the reaction chamber by a process comprising: introducing an etching gas into the plasma CVD chamber; applying a pulse amplitude modulated high frequency voltage through the pulse amplitude modulation circuit to the first electrode by changing the first change-over switch; and applying a high frequency voltage having a phase, which is shifted by 180° from the pulse amplitude modulated high frequency voltage, to the second electrode in order to produce plasma of said etching gas, wherein said high frequency voltage is pulse amplitude modulated through the pulse amplitude modulation circuit by changing the first change-over switch and directed through the inverter circuit by changing the second change-over switch.