Plasma processing device and plasma processing method

A plasma processing apparatus comprising:

• a processing chamber in which a sample is plasma processed;
• a radio frequency power supply which supplies radio frequency power for generating plasma;
• a sample stand on which the sample is placed;
• an optical system comprising an incident light source that emits incident ultraviolet-ray light onto a reference groove pattern on the sample, a detector which detects interference light reflected by the sample, and a spectrometer that disperses the interference light through an optical fiber and which transmits a reference spectrum of the interference light;
• and
• a control device configured to
• selectively deposit a protective film by partially depositing the protective film on a desired material of the sample, wherein the partially depositing the protective film is performed for less than a predetermined processing time;
• and
• receive the reference spectrum of the interference light transmitted by the spectrometer and (A) measure a thickness of the protective film formed on the desired material of the sample using the reference spectrum of the interference light reflected by the sample which has been irradiated with the ultraviolet-ray light, or (B) to determine selectivity of the protective film using the interference light reflected by the sample which has been irradiated with the ultraviolet-ray light, by determining, for each of (A) or (B), that the interference light reflected by the sample for the selectively-deposited protective film has a signal intensity that exceeds a stored signal intensity for the interference light reflected by the sample for a uniformly-deposited protective filmi by a first specified value for a first wavelength within the processing time, with respect to a case in which the selectively-deposited protective film is uniformly-deposited.