Wafer placement table

A wafer placement table comprising:

• a ceramic plate having a wafer placement surface on an upper surface;
• a cooling plate provided on a lower surface of the ceramic plate;
• and
• a refrigerant flow path provided inside the cooling plate,
• an annular focus-ring placement surface provided around the wafer placement surface of the ceramic plate and located at a lower level than the wafer placement surface;
• wherein the cooling plate is made of a material having a lower thermal conductivity than Al,
• wherein a length between an upper surface of the refrigerant flow path and the wafer placement surface is not constant and varies as being long in one part and short in another part,
• wherein a flow-path cross-sectional area of the refrigerant flow path is not constant and varies as being small in one part and large in another part, and
• wherein an aspect ratio defined as a ratio of a vertical length to a horizontal length of a flow-path cross section of the refrigerant flow path is not constant and varies as being small in one part and large in another part, and
• wherein the aspect ratio of the flow-path cross section of the refrigerant flow path in the portion corresponding to the focus-ring placement surface is smaller than the aspect ratio of the flow-path cross section of the refrigerant flow path in the portion corresponding to the central area of the wafer placement surface.