Substrate table, lithographic apparatus, sticker, cover ring and method of operating a lithographic apparatus

1 . A substrate table for use in an immersion lithographic apparatus, the substrate table comprising a support area defining a support plane to support a substrate to be patterned and an upper surface surrounding the support area, wherein:

the upper surface comprises an outer region that is substantially planar and a transition region proximate the support area;

the transition region is a separate structure from the outer region; and

the transition region is not co-planar with the outer region so as to ameliorate a level transition between the outer region and a non-standard substrate, which has a thickness different than a distance between the support plane and a nominal plane defined by the outer region.

2 . The substrate table of claim 1 , wherein the transition region forms an annulus surrounding the support area or extends along one or more discrete regions around the support area.

3 . The substrate table of claim 1 , wherein the innermost edge of the transition region is spaced from the outer edge of the support area by no more than 3 mm.

4 . The substrate table of claim 1 , wherein the transition region comprises a sticker adhered to a surface substantially coplanar with the outer region.

5 . The substrate table of claim 4 , wherein the transition region comprises a further sticker adhered to the sticker.

6 . The substrate table of claim 4 , wherein the substrate table comprises a body that defines the outer region and a cover ring surrounding the support area, and the sticker bridges a gap between the cover ring and the outer region; and/or wherein the sticker is made of a polymer.

7 . The substrate table of claim 1 , wherein the substrate table comprises a body that defines the outer region and a cover ring surrounding the support area, wherein the cover ring defines the transition region.

8 . The substrate table of claim 7 , wherein the cover ring comprises a lower ring part and an upper ring part, the upper ring part defining the transition region, and an actuator configured to change the position of the upper ring part relative to the nominal plane; or further comprising an actuator connected to the cover ring and configured to selectively alter the profile of the transition region.

9 . The substrate table of claim 8 , wherein the actuator is configured to alter or change the shape of at least part of the cover ring.

10 . The substrate table of claim 9 , wherein the actuator is configured to alter or change the shape of the cover ring between a first configuration in which the transition region conforms to a plane and a second configuration in which the transition region is a part conical surface.

11 . The substrate table of claim 8 , wherein the actuator is configured to act between the cover ring and a main body of the substrate table or wherein the actuator is integrated in the cover ring and acts between two parts thereof.

12 . The substrate table of claim 11 , wherein the actuator is configured to rotate one part of the cover ring relative to the other.

13 . The substrate table of claim 7 , wherein the cover ring comprises an upper ring part and a lower ring part, the upper ring part defining the transition region and being separable from the lower ring part.

14 . An immersion lithographic apparatus comprising:

the substrate table according to claim 1 ;

a liquid confinement system configured to confine an immersion liquid to a space; and

a positioning system configured to position the substrate table relative to the liquid confinement system.

15 . The substrate table of claim 1 , wherein at least part of the transition region is at a distance from the nominal plane of greater than 10 pm, and/or wherein no part of the transition region is further than 300 pm from the nominal plane, and/or wherein the transition region comprises a slope region that is inclined relative to the nominal plane and adjacent the outer region, and/or wherein the transition region comprises at least one step, and/or wherein the transition region projects upwardly or extends downwardly from the outer region.

16 . A sticker for use with a substrate table of an immersion lithographic apparatus, the sticker having a shape and configuration to define a transition region of an upper surface of the substrate table, the transition region being effective to reduce a level transition between an outer region of the upper surface of the substrate table and a substrate held by the substrate table, the substrate having a thickness greater than the height of the upper surface of the outer region relative to the support plane for the substrate.

17 . The sticker of claim 16 , wherein the transition region comprises a further sticker adhered to the sticker.

18 . A cover ring for use with a substrate table of an immersion lithographic apparatus, the cover ring having a shape and configuration to define a transition region of an upper surface of the substrate table, the transition region being effective to reduce a level transition between an outer region of the upper surface of the substrate table and a substrate held by the substrate table, the outer region being a separate structure from the cover ring and the substrate having a thickness different than the height of the upper surface of the outer region relative to the support plane for the substrate.

19 . The ring of claim 18 , comprising an upper ring part and a lower ring part, the upper ring part defining the transition region and being separable from the lower ring part.

20 . The ring of claim 19 , further comprising an actuator configured to change the position of the upper ring part relative to the lower ring part.