Plasma processing apparatus and plasma processing method

A plasma processing method for processing a sample that is an object to be processed by plasma, by mounting the sample on an upper surface of a sample stage arranged in a processing chamber inside a vacuum container and forming the plasma in the processing chamber,

• the sample stage including a refrigerant inlet and a refrigerant outlet arranged in each of a plurality of refrigerant channels that are concentrically arranged inside the sample stage and configured to allow a refrigerant to flow inside, and configured to function as a first evaporator,
• wherein the sample stage is included in a refrigeration cycle including a plurality of upstream-side expansion valves and a plurality of downstream-side expansion valves connected to the respective refrigerant inlets and the respective refrigerant outlets to adjust a flow rate or a pressure of a refrigerant flowing into the respective refrigerant inlets and a flow rate or a pressure of a refrigerant flowing out from the respective refrigerant outlets, in which a compressor, a condenser, the plurality of upstream-side expansion valves, the plurality of refrigerant channels, the plurality of downstream-side expansion valves and a second evaporator are connected in this order via a refrigerant duct to allow the refrigerant to flow therethrough in the recited order, the method comprising:
• adjusting openings of the plurality of upstream-side expansion valves and openings of the plurality of downstream-side expansion valves so that no change in flow rate of the refrigerant occurs in a plurality of refrigerant paths between the plurality of upstream-side expansion valves and the plurality of downstream-side expansion valves via the plurality of refrigerant channels.