Two-dimensionally balanced positioning device with two object holders, and lithographic device provided with such a positioning device.
A positioning device (3, 97, 179) with a first displacement unit (25, 189) for displacing a first object holder (11, 181) and a second displacement unit (27, 191) for displacing a second object holder (13, 183). The object holders can be displaced by the positioning device alternately from a measuring position into an operational position and can be displaced by the respective displacement units independently of one another in the measuring position and in the operational position.
The displacement units are provided with force actuators which each have a first part (47, 49; 117, 119; 215, 217) which is coupled to the relevant object holder and which is displaceable under the influence of a driving force relative to a second part (59, 61; 133, 135, 137, 139; 219, 221) which is fastened to a balancing unit (69, 149, 205) which is common to the two displacement units. The balancing unit is displaceably guided relative to a base (81, 209), so that reaction forces of the displacement units are converted into displacements of the balancing unit relative to the base, and mechanical vibrations in the balancing unit and the base are prevented. The use of the force actuators prevents the displacements of the balancing unit from disturbing the positions of the object holders relative to the base.
The positioning device is further provided with a control unit (83, 169, 237) by means of which at least the parts (47, 49; 121, 123; 219, 221) directed parallel to an X-direction of the X-actuators (39, 41; 105, 107; 211, 213) coupled to the object holders are held in positions parallel to the X-direction. It is also prevented in this manner that positions of the object holders relative to the base are interfered with by rotations of the balancing unit caused by the reaction forces of the displacement units.
The positioning device can be used in a lithographic device for the displacement of a semiconductor substrate relative to an exposure system of the lithographic device and for the displacement of a mask relative to the exposure system.