Plasma processing apparatus

A plasma processing apparatus comprising:

• a vacuum vessel including therein a processing chamber, having a reduced pressure, to which process gas is supplied;
• a stage disposed at an inner lower position of the processing chamber, the stage having an upper surface, and configured to mount a wafer to be processed, on the upper surface;
• a plasma generation chamber disposed above the processing chamber, wherein plasma is generated in the plasma generation chamber using the process gas;
• a plate member made of a dielectric material disposed above the upper surface of the stage and between the processing chamber and the plasma generation chamber, the plate member having a plurality of introduction holes for introducing the process gas;
• a lamp arranged to circumferentially surround the plate member, and configured to heat the wafer;
• an external infrared (IR) light source for determination of a wafer temperature;
• a spectroscope;
• and
• a detector configured to detect dispersed IR light, wherein
• the stage has a plurality of fiber installation openings,
• each of the plurality of fiber installation openings receives:
• an IR light emission fiber configured to output, from a rear side of the wafer, IR light from the external IR light source for determination of the wafer temperature, and
• an IR light collection fiber configured to collect IR light passing through, and reflected by, the wafer,
• an optical path switch configured to switch on and off IR light emission to the wafer, and a light splitter configured to split IR light into multiple beams, are both provided at an intermediate location on the IR light emission fiber,
• a plurality of the IR light collection fibers are connected to an optical multiplexer, and
• IR light corresponding to a selected one of the channels of the optical multiplexer is transmitted to the spectroscope, and is measured by the detector.