Patent ID: 8855949

Claim:
A plasma processing device comprising: a vacuum chamber that forms a processing chamber; an electrode portion arranged in the processing chamber and electrically isolated from the vacuum chamber; an vacuum exhaust portion configured to exhaust a gas from the processing chamber by vacuum; a gas supply portion configured to supply a gas which is used for plasma generation into the processing chamber; a high frequency power supply portion configured to generate plasma discharge in the processing chamber when a high frequency voltage is impressed onto the electrode portion; a matching device configured to match an impedance of a plasma discharge circuit configured to generate the plasma discharge with an impedance of the high frequency power supply portion; a discharge detection sensor comprising, at least, a plate-shaped dielectric member arranged such that one surface thereof opposes plasma discharge generated in the processing chamber, and a probe electrode arranged on the other surface of the dielectric member; and a signal analyzing portion configured to determine a signal of a potential change induced in the probe electrode in response to a change in the plasma discharge and execute analysis processing for monitoring a state of discharge, wherein said plasma processing device is configured to execute plasma processing for an object to be processed which is placed on the electrode portion to plasma processing, wherein the signal analyzing portion comprises: a first detector configured to determine a signal of a potential change induced by first arc discharge generated between the electrode portion and the object to be processed; a second detector configured to determine a signal of a potential change induced by second arc discharge other than the first arc discharge; and an abnormal discharge determining portion configured to obtain a difference between a number of determinations by the first detector and a number of determinations by the second detector within predetermined time, to compare the difference with a threshold value, and to determine that there is a possibility of generation of abnormal discharge in the processing chamber if the difference exceeds the threshold value, wherein a first threshold value for determining the signal of the potential change induced by the first arc discharge is set in the first detector, wherein a second threshold value for determining the signal of the potential change induced by the second arc discharge is set in the second detector, wherein an absolute value of the second threshold value is larger than an absolute value of the first threshold value, and wherein a positive or negative sign of the first threshold value is opposite to that of the second threshold value.