To provide a clean surface while eliminating a modified layer formed in a magnesium oxide surface as a protecting film by forming a protecting film for coating a dielectric layer of a front surface plate of one boards arranged opposite to each other in both sides of a gas space.
Plasma processing by the plasma to be generated by electrifying an electrode formed in a front surface plate in the atmosphere of the stabilized gas is desirable, and as the stabilized gas 3, at least one kind or more of the gas obtained by including oxygen in the penning gas, an inert gas such as argon and xenon, and nitrogen and oxygen is desirably included. The front surface plate 5 formed with a protecting film is set in a vacuum vessel 1. Air is evacuated for vacuum so as to set the inside of the vessel at 1×10-5 (Toor) or less, and the stabilized gas is led into the vessel, and voltage is applied. Discharge is maintained, for example, for three hours. With this structure, oxygen in the stabilized gas 3 is activated, and the carbon compound in the surface is decomposed so as to gasify the carbon.
YUHARA AKITSUNA
OTA YASUHIRO
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