Patent ID: 8349127
Filing Date: 2013-01-08
Classification: H01L

Abstract:
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.