Substrate support, method of compensating unflatness of an upper surface of a substrate, lithographic apparatus and device manufacturing method

1. A substrate support, comprising:

a support body forming a support surface configured to support a substrate, wherein the support surface comprises a support surface part configured to support a substrate area of the substrate, wherein the substrate area is a substrate edge area of the substrate and wherein the support surface part is a support surface edge part configured to support the substrate edge area of the substrate; and

a plurality of actuators arranged on the support body at locations aligned with the support surface part and configured to contract or extend in a direction substantially parallel to a main plane of the support surface,

wherein the support surface edge part has a reduced thickness with respect to a center part of the support body, the edge part forming the support surface edge part, wherein at least a subset of the plurality of actuators are arranged on the edge part, and

wherein, upon actuation, at least one actuator is configured to bend a portion of the support surface edge part to compensate an unflatness of an upper surface of an area of the substrate loaded on the support surface.

2. The substrate support of claim 1 , wherein the plurality of actuators comprises piezo actuators.

3. The substrate support of claim 1 , wherein the support surface is formed by multiple burls of the support body, each burl having a longitudinal axis perpendicular to the support surface, wherein a first burl and a second burl are spaced from each other in a direction substantially perpendicular to an edge of the substrate loaded on the support surface, and wherein the plurality of actuators are arranged to contract or extend in a direction parallel to a line between the longitudinal axis of the first burl and the second burl.

4. The substrate support of claim 1 , wherein the support surface edge part of the support surface comprises a circumferential area of the support surface, and wherein the plurality of actuators are distributed over the circumferential area.

5. The substrate support of claim 4 , wherein the substrate support comprises a control device, wherein the plurality of actuators are piezo actuators actuated by one of:

a single control signal of the control device, and

an individual control signal of the control device.

6. The substrate support of claim 1 , wherein the support body comprises an undercut aligned with a part forming the support surface part, wherein the subset of actuators is arranged on the undercut.

7. The substrate support of claim 1 , wherein the substrate support comprises a sensor device configured to measure the unflatness of an upper surface of an area of a substrate loaded on the support surface.

8. A method of compensating an unflatness of an upper surface of a substrate area of a substrate loaded on a support surface of a support body of a substrate support, wherein the substrate support comprises at least one actuator mounted on a substrate edge area of the support body and configured to contract or extend in a direction substantially parallel to a main surface of the substrate loaded on the substrate support, wherein the support surface edge part has a reduced thickness with respect to a center part of the support body, the edge part forming the support surface edge part, wherein at least a subset of the plurality of actuators are arranged on the edge part, and wherein the method comprises:

actuating at least one actuator to extend and/or contract to bend a portion of the support surface edge part on the basis of data representative of unflatness of the upper surface of the substrate area of the substrate loaded on the substrate support to create a curve in the support body, wherein the curve of the support body substantially compensates the unflatness of the upper surface of the substrate area.

9. The method of claim 8 , wherein the step of providing data comprises measuring the unflatness of the support surface of the substrate support.

10. The method of claim 8 , wherein the step of providing data comprises measuring the unflatness of at least the substrate area of the substrate.

11. The method of claim 10 , wherein the step of measuring the unflatness of at least the substrate area of the substrate is carried out when the substrate is loaded on the support surface.

12. A lithographic apparatus configured to transfer a pattern from a patterning device onto a substrate, comprising:

a substrate support, the substrate support comprising:

a support body forming a support surface configured to support a substrate, wherein the support surface comprises a support surface part configured to support a substrate area of the substrate, wherein the substrate area is a substrate edge area of the substrate and wherein the support surface part is a support surface edge part configured to support the substrate edge area of the substrate; and

a plurality of actuators arranged on the support body at locations aligned with the support surface part and configured to contract or extend in a direction substantially parallel to a main plane of the support surface,

wherein the support surface edge part has a reduced thickness with respect to a center part of the support body, the edge part forming the support surface edge part, wherein at least a subset of the plurality of actuators are arranged on the edge part, and

wherein, upon actuation, at least one actuator is configured and arranged to bend a portion of the support surface edge part to compensate an unflatness of an upper surface of an area of the substrate loaded on the support surface.

13. A device manufacturing method comprising transferring a pattern from a patterning device onto a substrate, wherein the method comprises:

loading the substrate on a support surface of a support body of a substrate support, wherein the substrate support comprises at least one actuator mounted on a substrate edge area of the support body and configured to contract or extend in a direction substantially parallel to a main surface of the substrate loaded on the substrate support, wherein the support surface edge part has a reduced thickness with respect to a center part of the support body, the edge part forming the support surface edge part, wherein at least a subset of the plurality of actuators are arranged on the edge part,

wherein the loading comprises actuating the at least one actuator to extend and/or contract to bend a portion of the support surface edge part on the basis of data representative for unflatness of the upper surface of the substrate area of the substrate loaded on the substrate support, in order to create a curve in the support body, wherein the curve of the support body substantially compensates the unflatness of the upper surface of the substrate area.