PLASMA PROCESSING APPARATUS AND PLASMA PROCESSING METHOD

1 . A plasma processing apparatus including a processing chamber that is arranged in a vacuum container and allows plasma to be formed therein, a sample stage on which a sample, which is an object to be processed by the plasma, is mounted, the sample stage including a plurality of refrigerant channels that are concentrically arranged and allow a refrigerant to flow inside and functioning as a first evaporator, a refrigerant inlet and a refrigerant outlet arranged in each of the plurality of refrigerant channels, and an exhaust unit that exhausts an inside of the processing chamber for pressure reduction, the apparatus comprising:

a plurality of upstream-side expansion valves and a plurality of downstream-side expansion valves that are connected to the respective refrigerant inlets and the respective refrigerant outlets and 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; and a refrigeration cycle including 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 connected in this order via a refrigerant duct, and allowing the refrigerant to flow in the order, wherein openings of the plurality of upstream-side expansion valves and openings of the plurality of downstream-side expansion valves are adjusted 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.

2 . The plasma processing apparatus according to claim 1 , wherein the openings of the plurality of upstream-side expansion valves and the openings of the plurality of downstream-side expansion valves are adjusted so that no change in flow rate of the refrigerant occurs in the plurality of refrigerant paths, the flow rate being detected based on a result of detection by each of detectors that are arranged on a plurality of refrigerant ducts between the plurality of upstream-side expansion valves and the respective refrigerant inlets of the plurality of refrigerant channels and detect respective temperatures of the refrigerants flowing in the respective refrigerant ducts.

3 . The plasma processing apparatus according to claim 1 , wherein the plurality of refrigerant channels include a center-side refrigerant channel arranged on a center side of the sample stage and an outer periphery-side refrigerant channel arranged on an outer periphery side of the sample stage, and the openings of the plurality of upstream-side expansion valves and the openings of the plurality of downstream-side expansion valves are adjusted so that a sum of reciprocals of respective refrigerant conductances of the upstream-side expansion valve and the downstream-side expansion valves connected to the center-side refrigerant channel is equal to a sum of reciprocals of respective refrigerant conductances of the upstream-side expansion valve and the downstream-side expansion valve connected to the outer periphery-side refrigerant channel.

4 . The plasma processing apparatus according to claim 1 , wherein the plurality of refrigerant channels include a center-side refrigerant channel arranged on a center side of the sample stage and an outer periphery-side refrigerant channel arranged on an outer periphery side of the sample stage, the plurality of upstream-side expansion valves and the plurality of downstream-side expansion valves include a common configuration, and the openings of the plurality of upstream-side expansion valves and the openings of the plurality of downstream-side expansion valves are adjusted so that a sum of reciprocals of the openings of the upstream-side expansion valve and the downstream-side expansion valve connected to the center-side refrigerant channel is equal to a sum of reciprocals of the openings of the upstream-side expansion valve and the downstream-side expansion valve connected to the outer periphery-side refrigerant channel.

5 . The plasma processing apparatus according to claim 4 , wherein the openings of the plurality of upstream-side expansion valves and the openings of the plurality of downstream-side expansion valves are adjusted so that a sum of the opening of the downstream-side expansion valve connected to the center-side refrigerant channel and the opening of the upstream-side expansion valve connected to the outer periphery-side refrigerant channel is equal to a sum of the opening of the upstream-side expansion valve connected to the center-side refrigerant channel and the opening of the downstream-side expansion valve connected to the outer periphery-side refrigerant channel.

6 . The plasma processing apparatus according to claim 1 , further comprising a main line and a bypass line that is arranged in parallel to the main line and includes a capillary with a small conductance, the main line and the bypass line allowing the refrigerant to flow therethrough, a valve that is provided on an upstream side of each of the main line and the bypass line to open/close the respective line, and a thermometer provided on a downstream side of the main line and the bypass line, between the condenser and the plurality of upstream-side expansion valves.

7 . 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 allow a refrigerant to flow inside, and functioning as a first evaporator,

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 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.

8 . The plasma processing method according to claim 7 , wherein the openings of the plurality of upstream-side expansion valves and the openings of the plurality of downstream-side expansion valves are adjusted so that no change in flow rate of the refrigerant occurs in the plurality of refrigerant paths, the flow rate being detected based on a result of detection by each of detectors that are arranged on a plurality of refrigerant ducts between the plurality of upstream-side expansion valves and the respective refrigerant inlets of the plurality of refrigerant channels and detect respective temperatures of the refrigerants flowing in the respective refrigerant ducts.

9 . The plasma processing method according to claim 7 ,

wherein the plurality of refrigerant channels include a center-side refrigerant channel arranged on a center side of the sample stage and an outer periphery-side refrigerant channel arranged on an outer periphery side of the sample stage; and

wherein the openings of the plurality of upstream-side expansion valves and the openings of the plurality of downstream-side expansion valves are adjusted so that a sum of reciprocals of refrigerant conductances of the upstream-side expansion valve and the downstream-side expansion valve connected to the center-side refrigerant channel is equal to a sum of reciprocals of refrigerant conductances of the upstream-side expansion valve and the downstream-side expansion valve connected to the outer periphery-side refrigerant channel.

10 . The plasma processing apparatus according to claim 7 ,

wherein the plurality of refrigerant channels includes a center-side refrigerant channel arranged on a center side of the sample stage and an outer periphery-side refrigerant channel arranged on an outer periphery side of the sample stage, and the plurality of upstream-side expansion valves and the plurality of downstream-side expansion valves include a common configuration; and

wherein the openings of the plurality of upstream-side expansion valves and the opening of the plurality of downstream-side expansion valves are adjusted so that a sum of reciprocals of the openings of the upstream-side expansion valve and the downstream-side expansion valve connected to the center-side refrigerant channel is equal to a sum of reciprocals of the openings of the upstream-side expansion valve and the downstream-side expansion valve connected to the outer periphery-side refrigerant channel.

11 . The plasma processing method according to claim 10 , wherein the openings of the plurality of upstream-side expansion valves and the openings of the plurality of downstream-side expansion valves are adjusted so that a sum of the opening of the downstream-side expansion valve connected to the center-side refrigerant channel and the opening of the upstream-side expansion valve connected to the outer periphery-side refrigerant channel is equal to a sum of the opening of the upstream-side expansion valve connected to the center-side refrigerant channel and the opening of the downstream-side expansion valve connected to the outer periphery-side refrigerant channel.