Patent ID: 7193493
Filing Date: 2007-03-20
Classification: G03F,Y10T

Abstract:
1. An alignment apparatus comprising: a structure to be aligned; a moving member which moves to align said structure; and an electromagnetic mechanism which electromagnetically applies a force between said structure and said moving member to allow said structure to move along with movement of said moving member while forming a gap between said structure and said moving member, said electromagnetic mechanism having: (a) a first electromagnetic actuator which is feedback-controlled on the basis of a deviation between a target position and an actual position of said structure; and (b) a second electromagnetic actuator which is feedforward-controlled on the basis of the target position of said structure; and each of the first and second electromagnetic actuators having: (i) a pair of electromagnets which are so arranged as to generate forces in opposite directions on the same line; and (ii) a pair of targets which are arranged to face the pair of electromagnets, wherein an attractive force by a magnetic flux generated by the electromagnet acts on the target between the electromagnet and the target, and wherein in feedback control, a current supplied to a coil of the electromagnet is controlled in accordance with a value calculated by multiplying a square root of a force to be generated by the first electromagnetic actuator in order to reduce the deviation, by a correction term corresponding to a gap between the electromagnet and the target in the first electromagnetic actuator.