Patent Number: 051611775
Section: claims

1. A substrate holding apparatus for holding a substrate to be exposed by radiation, which is transported by a substrate transporting apparatus, said apparatus comprising: a substrate stage having a substrate holding surface for attracting a substrate, said substrate holding surface being divided into an inner peripheral portion and an outer peripheral portion by at least a groove formed in said substrate stage;  a magnetic member fitted into said groove of said substrate stage;  at least a magnetic unit embedded in said magnetic member, said magnetic unit including a permanent magnet and an electromagnet for eliminating a magnetic force of said permanent magnet when energized; and  moving means for moving said magnetic member together with said magnetic unit in a direction of the depth of said groove between a first position in which the magnetic force of said permanent magnet is effective for the substrate on said substrate holding surface and a second position in which the magnetic force of said permanent magnet is ineffective for the substrate on said substrate holding surface.  a substrate stage having a substrate holding surface for attracting a substrate;  at least a magnetic unit movably disposed in said substrate stage, said magnetic unit including a permanent magnet and an electromagnet for eliminating a magnetic force of said permanent magnet when energized; and  moving means for moving said magnetic unit between a first position in which the magnetic force of said permanent magnet is effective for the substrate on said substrate holding surface and a second position in which the magnetic force of said permanent magnet is ineffective for the substrate on said substrate holding surface.  bringing the magnetic unit to the second position;  putting the substrate on the substrate holding surface by a substrate transporting apparatus;  bringing the magnetic unit to the first position;  disabling the electromagnet;  releasing the substrate from the substrate transporting apparatus;  re-grasping the substrate by the substrate transporting apparatus;  energizing the electromagnet;  bringing the magnetic unit to the second position;  disabling the electromagnet;  positioning the substrate by the substrate transporting apparatus;  energizing the electromagnet;  bringing the magnetic unit to the first position;  disabling the electromagnet; and  releasing the substrate from the substrate transporting apparatus. 2. A substrate holding apparatus according to claim 1, wherein said groove has a stepped portion formed between a narrow-width portion at the side of said substrate holding surface and a wide-width portion at its bottom side, said magnetic member includes an upper portion whose width is substantially equal to that of said narrow-width portion of said groove and a bottom portion whose width is substantially equal to that of said wide-width portion of said groove and which forms a space between said bottom portion and said wide-width portion and said moving means comprises means for selectively supplying gas to and discharging gas from said space. 3. A substrate holding apparatus according to claim 2, further comprising sealing means for sealing said space. 4. A substrate holding apparatus according to claim 1, wherein said groove of said substrate stage is continuously formed along a periphery of said mask stage, a first screw is cut on a surface for defining an outer peripheral surface of said groove, a second screw engaging said first screw is cut on an outer peripheral surface of said magnetic member, longitudinal grooves are formed on the outer peripheral surface of said said magnetic member and said moving means includes a gear disposed in said substrate stage for engaging said longitudinal grooves and a motor for rotating said gear. 5. A substrate holding apparatus according to claim 1, wherein said substrate stage has an annular shape. 6. A substrate holding apparatus according to claim 1, wherein a plurality of said magnetic units are disposed equidistantly. 7. A substrate holding apparatus for holding a substrate to be exposed by radiation, which is transported by a substrate transporting apparatus, said apparatus comprising: 8. A method for positioning a substrate on a substrate holding surface of a substrate holding apparatus comprising a substrate stage having a substrate holding surface for attracting a substrate, at least one magnetic unit movably disposed in the substrate stage, the magnetic unit including a permanent magnet and an electromagnet for eliminating a magnetic force of the permanent magnet when energized and moving means for moving the magnetic unit 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, said method comprising the steps of: