Object table, a stage apparatus and a lithographic apparatus

1. An object table configured to hold an object on a holding surface, the object table comprising:

a main body;

a plurality of burls extending from the main body, end surfaces of the burls defining the holding surface;

an actuator assembly; and

a further actuator assembly,

wherein the actuator assembly is configured to deform the main body to generate a long-stroke out-of-plane deformation of the holding surface, based on shape information of the object that is to be held and the further actuator assembly is configured to generate a short stroke out-of-plane deformation of the holding surface.

2. The object table according to claim 1 , further comprising a clamp configured to exert a holding force on the object.

3. The object table according to claim 2 , wherein the clamp is an electrostatic clamp comprising one or more electrodes.

4. The object table according to claim 2 , wherein the actuator assembly is configured to generate the long-stroke out-of-plane deformation prior to the exertion of the holding force.

5. The object table according to claim 1 , wherein the plurality of burls are arranged on a top surface of the main body and wherein the actuator assembly is mounted to a bottom surface of the main body.

6. The object table according to claim 5 , wherein the actuator assembly comprises a plurality of protrusions extending from the bottom surface of the main body and a plurality of piezo-electric actuators, a piezo-electric actuator of the plurality of piezo-electric actuators connecting a pair of protrusions of the plurality of protrusions.

7. The object table according to claim 1 , wherein out-of-plane deformation causes a bending of the holding surface.

8. The object table according to claim 7 , wherein a neutral plane of an actuation of the object table is arranged to substantially coincide with a neutral plane of the object when subjected to a bending.

9. The object table according to claim 1 , wherein the further actuator assembly is configured to generate an in-plane deformation of the holding surface.

10. The object table according to claim 1 , wherein the further actuator assembly comprises a plurality of piezo-electric actuators.

11. The object table according to claim 1 , further comprising a control unit configured to control the actuator assembly.

12. The object table according to claim 11 , wherein the control unit is configured to:

receive the shape information of the object to be held, and

generate one or more control signals for the actuator assembly to generate an out-of-plane deformation of the holding surface.

13. The object table according to claim 1 , further comprising a control unit configured to control the actuator assembly and the further actuator assembly.

14. The object table according to claim 13 , wherein the control unit is configured to:

receive the shape information of the object to be held, and

generate one or more control signals for the actuator assembly and the further actuator assembly to generate an out-of-plane deformation of the holding surface.

15. The object table according to claim 1 , wherein the object table further comprises a sensor assembly configured to sense a shape of the object that is to be held.

16. A stage apparatus comprising the object table according to claim 1 .

17. The stage apparatus according to claim 16 , further comprising a positioning device configured to position the object table.

18. The stage apparatus according to claim 17 , wherein the positioning device comprises a long-stroke positioner and a short-stroke positioner.

19. The stage apparatus according to claim 17 , further comprising an interface assembly configured to hold the object table to the positioning device.

20. A lithographic apparatus comprising the stage apparatus according to claim 16 .