Alignment apparatus, exposure apparatus, and device manufacturing method
An alignment apparatus moves an X-Y slider together with X and Y beams. Electromagnetic guides (electromagnetic mechanisms) are interposed between the X-Y slider, the X beam, and the Y beam. The electromagnetic guides include alignment and acceleration electromagnets attached to the X-Y slider, and targets attached to the X and Y beams. The alignment electromagnet is feedback controlled, whereas the acceleration electromagnet is feedforward controlled.
1. An alignment apparatus comprising:
a structure to be aligned;
a moving member which has a magnetic member and moves in a first direction; and
an electromagnetic actuator unit, arranged on the structure, which applies a force in the first direction between said structure and said moving member, said electromagnetic actuator unit having:
(i) a first electromagnet actuator having at least a pair of electromagnets arranged to sandwich said moving member, the first electromagnet actuator generating an attractive force between the first electromagnet actuator and the magnetic member by a magnetic flux generated by each of the electromagnets; and
(ii) a second electromagnet actuator having at least a pair of electromagnets arranged to sandwich said moving member, the second electromagnet actuator generating an attractive force between the second electromagnet actuator and the magnetic member by a magnetic flux generated by each of the electromagnets,
wherein a first electromagnet is feedback-controlled on the basis of a deviation between a target position and an actual position of said structure, and
a second electromagnet actuator is feedforward-controlled on the basis of a target position of said structure.
2. The apparatus according to claim 1 , wherein said first electromagnet actuator has two pairs of electromagnets, said second electromagnet actuator has a pair of electromagnets, the apparatus further comprises two first electromagnets, and the pair of the electromagnets of said second electromagnet actuator is interposed between the two first electromagnets of said first electromagnet actuator.
3. The apparatus according to claim 1 , wherein a line of force generated by said second electromagnetic actuator passes through a barycenter of said structure.
4. The apparatus according to claim 1 , wherein a gap between said first electromagnet and said magnetic member is not less than a gap between said second electromagnet and said magnetic member.
5. The apparatus according to claim 1 , further comprising driving mechanisms which are arranged at two ends of said moving member to drive said moving member in the first direction, and said driving mechanisms are controlled on the basis of a position of said structure in a second direction perpendicular to the first direction.
6. The apparatus according to claim 5 , wherein said driving mechanisms are controlled on the basis of a barycentric position of said moving member so as to cancel a moment generated on said moving member by a reaction force generated by a force applied from said moving member to said structure.
7. An exposure apparatus comprising:
an alignment apparatus, as defined in claim 1 , to align a target object, and which executes an exposure operation.
8. A device manufacturing method comprising steps of:
using an exposure apparatus as defined in claim 7 ;
transferring a pattern onto a substrate; and
developing the substrate.
9. An alignment apparatus comprising:
a structure to be aligned;
a moving member which moves in a first direction; and
an electromagnetic actuator unit which applies a force in the first direction between said structure and said moving member, said electromagnetic actuator unit having:
(i) first and second electromagnets;
(ii) a magnetic member which forms a magnetic path in cooperation with said first electromagnet and said second electromagnet; and
(iii) a controller which controls a current supplied to a coil of said first electromagnet and said second electromagnet,
wherein said controller feedback controls said first electromagnet on the basis of a deviation between a target position and an actual position of said structure, and feedforward controls said second electromagnet on the basis of the target position of said structure, and
wherein said controller includes a calculation unit which calculates a correction value for correcting force changes generated by gap changes between said first and second electromagnets and said magnetic member, and said apparatus calculates a command current to said first electromagnet by multiplying the square root of a force command by a correction value calculated in said calculation unit.
10. The apparatus according to claim 9 , wherein said controller includes a conversion unit which converts the target position of said structure into a command value of a magnetic flux and a detection unit which detects a magnetic flux generated by said second electromagnet, and said apparatus controls said second electromagnet on the basis of a difference between the command value and the detection result.
11. The apparatus according to claim 9 , wherein a pair of said first and second electromagnets are so arranged as to sandwich said magnetic member, and said controller controls operation so as not to energize one of the pair of electromagnets while the other electromagnet is energized.