Patent ID: 8182660

Claim:
A power supply apparatus comprising: a substrate holder having an electrostatic chuck which generates an attracting force for holding a substrate, wherein a first electrode is arranged inside said electrostatic chuck and generates the attracting force; a strut which rotatably supports said substrate holder and is rotatable around a central axis; a rotational driving mechanism which rotates said substrate holder via said strut; a first housing configured to support said strut, wherein first electric power from a first external power supply connected to said first housing is supplied to the first electrode of said electrostatic chuck via said first housing; a first conductive annular member which is arranged around the central axis and is fixed to an end portion of said strut, and which is configured to rotate together with said strut; a second conductive annular member which is arranged around the central axis and is fixed to said first housing, and which is brought into direct surface contact with said first conductive annular member, wherein an upper surface of said second conductive annular member and a lower surface of said first conductive annular member have a surface contact sliding relationship; a third conductive annular member which is arranged around the central axis and is fixed to said strut, and which is configured to rotate together with said strut, wherein a first gap is formed between an inner circumferential surface of said first conductive annular member and an outer circumferential surface of said third conductive annular member; a fourth conductive annular member which is arranged around the central axis and is fixed to said first housing, wherein a second gap is formed between an inner circumferential surface of said second conductive annular member and an outer circumferential surface of said fourth conductive annular member, and an upper surface of said fourth conductive annular member and a lower surface of said third conductive annular member have a surface contact sliding relationship; a first power supply member which is arranged inside said strut and which supplies the first electric power to said first electrode of said electrostatic chuck via said first and second conductive annular members, and said third and fourth conductive annular members, wherein said first housing has a first channel which is formed to supply fluid into the first and second gaps.