Stage system, lithographic apparatus, method for positioning and device manufacturing method
A system for positioning, a stage system, a lithographic apparatus, a method for positioning and a method for manufacturing a device in which use is made of a stage system that includes a plurality of gas bearing devices. Each gas bearing device includes: a gas bearing body, which has a free surface, a primary channel which extends through the gas bearing body and has an inlet opening in the free surface, a secondary channel system which extends through the gas bearing body and which has a plurality of discharge openings in the free surface. The flow resistance in the secondary channel system is higher than the flow resistance in the primary channel.
1. An object table adapted to support an object to be positioned, the object table comprising:
a clamping device to clamp the object;
a plurality of burls configured to provide a support surface for the object; and
a plurality of gas bearing devices arranged to support the object prior to clamping of the object on the burls, wherein each gas bearing device is in fluid communication with a source of sub-atmospheric pressure configured to pull the object towards the surface and a source of pressurized gas configured to push the object away from the surface such that a balance between the pushing force that the pressurized gas exerts on the object and the pulling force that the sub-atmospheric pressure exerts on the object allows the object to be positioned in a direction perpendicular to the surface.
2. The table according to claim 1 , wherein each gas bearing device comprises a porous material comprising interconnected cavities.
3. The table according to claim 1 , wherein the plurality of gas bearing devices is adapted to change a shape of the object by controlling the pressure and/or gas flow rate at an inlet opening and/or the pressure and/or gas flow rate at a discharge opening, of at least one gas bearing device.
4. The table according to claim 3 , wherein control of the pressure and/or gas flow rate is based on an expected and/or measured shape of the object.
5. The table according to claim 4 , further comprising:
a measurement system configured to obtain shape data of the object when arranged on the object table during activation of the gas bearing devices, and
a control device configured to receive the shape data from the measurement system and to control the pressure and/or gas flow rate based on the received shape data.
6. A lithographic apparatus arranged to transfer a pattern from a patterning device onto a substrate, wherein the lithographic apparatus comprises the table according to claim 1 .
7. The table according to claim 1 , wherein at least one of the gas bearing devices comprises:
a gas bearing body having a free surface,
a primary channel which extends through the gas bearing body and has an inlet opening in the free surface, and
a secondary channel system which extends through the gas bearing body and has a discharge opening in the free surface.
8. The table according to claim 7 , wherein the primary channel is in fluid communication with the source of sub-atmospheric pressure and the secondary channel system is in fluid communication with the source of pressurized gas.
9. The table according to claim 7 , comprising a plurality of discharge openings surrounding the inlet opening.
10. The table according to claim 7 , wherein the flow resistance in the secondary channel system is higher than the flow resistance in the primary channel.
11. The table according to claim 7 , wherein the flow resistance in the secondary channel system is higher than the flow resistance in the gap between the free surface and the object.
12. An object table configured to support an object, the object table comprising:
a clamping device to clamp the object;
a plurality of burls configured to provide a support surface for the object; and
a plurality of gas bearing devices arranged to support the object prior to clamping by the clamping device of the object on the burls, each gas bearing device comprising:
a gas bearing body having a free surface,
a primary channel which extends through the gas bearing body and has an inlet opening in the free surface, and
a secondary channel system which extends through the gas bearing body and has a discharge opening in the free surface.
13. The table according to claim 12 , wherein the primary channel is in fluid communication with a source of sub-atmospheric pressure and the secondary channel system is in fluid communication with a source of pressurized gas.
14. The table according to claim 12 , comprising a plurality of discharge openings surrounding the inlet opening.
15. The table according to claim 12 , wherein the gas bearing body comprises a porous material comprising interconnected cavities, and the secondary channel system is formed by the interconnected cavities.
16. The table according to claim 12 , wherein the flow resistance in the secondary channel system is higher than the flow resistance in the primary channel.
17. The table according to claim 12 , wherein the flow resistance in the secondary channel system is higher than the flow resistance in the gap between the free surface and the object.
18. The table according to claim 12 , wherein the plurality of gas bearing devices is adapted to change a shape of the object by controlling the pressure and/or gas flow rate at the inlet opening and/or the pressure and/or gas flow rate at the discharge opening, of at least one gas bearing device.
19. The table according to claim 18 , further comprising:
a measurement system configured to obtain shape data of the object when arranged on the object table during activation of the gas bearing devices, and
a control device configured to receive the shape data from the measurement system and to control the pressure and/or gas flow rate based on the received shape.
20. A lithographic apparatus arranged to transfer a pattern from a patterning device onto a substrate, wherein the lithographic apparatus comprises the table according to claim 12 .