| 摘要 |
To monitor the thickness of a focus ring consumed during wafer processing. A plasma processing apparatus includes a vacuum chamber 1, workpiece mounting means 5, high frequency electric power introducing means 4 and radio-frequency bias electric power introducing means 7 and processes a surface of a workpiece 6 using a plasma that is converted from a gas introduced into the vacuum chamber 1 by the action of a high frequency electric power introduced by the high frequency electric power introducing means 4. The plasma processing apparatus further includes an annular member 11 surrounding the workpiece 6 mounted on the workpiece mounting means 5, and a pair of tubes having an aspect ratio of 3 or higher and disposed on a side wall of the vacuum chamber 1 to face each other. Each tube is vacuum-sealed at a tip end thereof with a glass material. One of the tubes has a light source 15 disposed facing to the interior of the vacuum chamber on the atmosphere side of the glass material, and the other tube has light receiving means 16 disposed facing to the interior of the vacuum chamber on the atmosphere side of the glass material. The light receiving means 16 receives light passing across the surface of the annular member 11.
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