Patent ID: 7169254

Claim:
A plasma processing apparatus for processing a sample disposed inside a vacuum chamber using a plasma generated therein comprising: an electrically conductive member disposed above said sample which is disposed inside said vacuum chamber, said electrically conductive member being supplied with electric power for generating said plasma thereunder; a plate member which is disposed so as to have a front part which opposes and faces said sample and constitutes a portion of a ceiling of a processing chamber of said vacuum chamber in which said sample is processed, said plate member being disposed under said electrically conductive member and electrically coupled to said electrically conductive member; an optical transmitter mounted with respect to said vacuum chamber so as to be almost in contact with or spaced apart from a back part of said plate member at an opening of a through-hole in said plate member which is open to said vacuum chamber, said opening having a smaller diameter than a diameter of said optical transmitter, and said optical transmitter being disposed so as to receive light from said vacuum chamber via said opening of said through-hole; a holder disposed at an upper side of said electrically conductive member which holds said optical transmitter with respect to said vacuum chamber; a seal which seals a vacuum side and an atmospheric side of said vacuum chamber with respect to said holder which holds said optical transmitter; and a detector which detects said light received by said optical transmitter and which is transmitted through said optical transmitter; wherein said optical transmitter is mounted with respect to said vacuum chamber so as to be detachable from a back part side of said plate member out of said atmospheric side thereof.