Vacuum processing apparatus and plasma processing apparatus with temperature control function for wafer stage
View Patent ↗A wafer stage includes a first evaporator where a refrigerant circulates. The first evaporator makes up a cooling cycle with a compressor, first condenser, expansion valve, second evaporator, refrigerant thermometer, and refrigerant flowmeter. The first condenser is supplied with a heat exchange medium. The temperature of a coolant supplied to the second evaporator is measured by an inlet refrigerant thermometer and outlet refrigerant thermometer, while the flow rate of the coolant is monitored and adjusted by a flow-rate adjuster. The temperature difference in the coolant between being at the inlet and at the outlet and flow rate can be measured. Upon complete evaporation of the refrigerant in the second evaporator, the dryness of the refrigerant discharged from the wafer stage is calculated from the amount of heat absorbed from (exchanged with) the coolant, the circulation amount of the refrigerant and the refrigerant temperature to control the rotational speed of the compressor.
1. A vacuum processing apparatus that includes a wafer stage disposed in a vacuum processing chamber, converts process gas introduced into the vacuum processing chamber into plasma and performs surface treatment to a wafer placed on the wafer stage with the plasma, the vacuum processing apparatus comprising:
a cooling cycle including a refrigerant passage that is provided in the wafer stage and serves as an evaporator, and a compressor, a condenser and an expansion valve that are disposed outside the vacuum processing chamber; and
a suction tank that is disposed between the evaporator and the compressor in the cooling cycle;
wherein the rotational speed of the compressor is controlled according to the degree of dryness of a refrigerant in the refrigerant passage at least when the refrigerant has passed through the wafer stage to reduce the amount of the refrigerant circulating in the cooling cycle within a range in which dry-out does not occur in the evaporator; and
wherein the degree of dryness of the refrigerant is detected in accordance with the state of a liquid refrigerant in the suction tank.
2. The vacuum processing apparatus according to claim 1 ,
wherein the rotational speed of the compressor is controllably reduced to a low speed within a range in which the degree of dryness is from 0.6 to 0.9 and dry-out does not occur.
3. The vacuum processing apparatus according to claim 1 ,
wherein the cooling cycle includes,
the refrigerant passage that is provided in the wafer stage and serves as a first evaporator, and
the compressor, a first condenser and the expansion valve that are disposed outside the vacuum processing chamber,
the vacuum processing apparatus further comprising:
a second evaporator that is disposed between the first evaporator and the compressor in the cooling cycle; and a heat medium passage that supplies a heat exchange medium to the second evaporator,
wherein the temperature difference in the heat exchange medium between when the heat exchange medium is supplied and when the heat exchange medium is discharged, the flow rate of the heat exchange medium, the amount of the refrigerant circulating in the cooling cycle and the refrigerant temperature are measured to obtain the degree of dryness of the refrigerant having passed through the first evaporator, and
wherein the rotational speed of the compressor is controlled according to the degree of dryness.
4. The vacuum processing apparatus according to claim 3 ,
wherein the passages for the heat exchange medium supplied to the first condenser and the second refrigerant evaporator in the cooling cycle are arranged in series as a heat medium passage.