Patent Number: 051611775
Section: abstract

A substrate holding apparatus for vertically holding a substrate to be exposed by radiation includes a substrate stage having a substrate holding surface for attracting a substrate. The substrate holding surface is divided into an inner peripheral portion and an outer peripheral portion by a groove formed in the substrate stage. A magnetic member is fitted into the groove of the substrate stage, and at least a magnetic unit is embedded in the magnetic member. The magnetic unit includes a permanent magnet and an electromagnet for eliminating a magnetic force of the permanent magnet when energized. Further, a moving device is provided for moving the magnetic member together with the magnetic unit in a direction of the depth of the groove between a first position in which the magnetic force of the permanent magnet is effective for the substrate on the substrate holding surface and a second position in which the magnetic force of the permanent magnet is ineffective for the substrate on the substrate holding surface. The electromagnet need not be energized during a substrate positioning period if the magnetic member with the magnetic unit is brought to the second position.