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1. WO2020135971 - SUBSTRATE HOLDER FOR USE IN A LITHOGRAPHIC APPARATUS AND A METHOD OF MANUFACTURING A SUBSTRATE HOLDER

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[ EN ]

CLAIMS

1. A method of producing a substrate holder for use in a lithographic apparatus, the substrate holder comprising a main body having a main body surface, wherein the method includes the steps of:

coating at least part of the main body with a layer of a first coating material; and

treating a plurality of discrete regions of the first coating material with laser irradiation to selectively convert said first coating material in said regions to a second coating material having a different structure or density.

2. A method according to claim 1 wherein the substrate holder further comprises a plurality of burls projecting from the main body surface and each having a distal end surface configured to engage with the substrate, and wherein:

the step of coating coats at least the distal end surface of a plurality of said burls with a layer of said first coating material; and

the step of treating treats at least a plurality of discrete regions of said distal end surfaces with said laser irradiation.

3. A method according to claim 2, wherein the method is a method of repairing an existing substrate holder in which one or more of said burls has been worn down at the distal end surface, and the steps of coating and treating coat and treat the distal end surface of said worn down burls.

4. A method according to claim 1 wherein the steps of coating and treating are performed repeatedly to build up said discrete regions to form burls projecting from the main body of the substrate holder.

5. A method according to claim 1 wherein the first coating material is a mask having a plurality of holes in it and the step of treating treats regions in said holes and is repeated to form burls in said holes.

6. A method according any one of the preceding claims further including the step of removing the untreated areas of said first coating material.

7. A method according to any one of the preceding claims wherein the second coating material is harder than the first coating material.

8. A method according to claim 7 wherein the second coating material is one of diamond, cubic-BN, C3N4, a metal boride, S13N4 or SiC or a material comprising at least two of: C, B, N, Si.

9. A method according to any one of the preceding claims wherein the step of treating applies different laser irradiation to different ones of said discrete regions, such that at least one property of the second coating material differs between said regions.

10. A method according to claim 9 wherein the step of treating applies different laser irradiation to one or more burls in an outer region of the substrate holder compared to one or more burls in an inner region of the substrate holder, such that the second coating material of the burls in the outer region is harder and/or thicker and/or has different coefficient of friction than the second coating material of the burls in the inner region.

11. A method according to any one of the preceding claims wherein the discrete regions include distal end surfaces of a plurality of burls projecting from the main body surface.

12. A method according to any one of the preceding claims wherein the discrete regions include discrete regions on a distal end surface of a single burl.

13. A method according to any one of the preceding claims wherein the step of treating creates a plurality of seed crystals of the second coating material and further including the step of growing said second coating material on said seed crystals.

14. A substrate holder for use in a lithographic apparatus and configured to support a substrate, the substrate holder comprising:

a main body having a main body surface;

a plurality of burls projecting from the main body surface, wherein:

each burl has a distal end surface which is configured to engage with the substrate; the distal end surfaces of the burls substantially conform to a support plane and are configured for supporting the substrate; and

the distal end surfaces of at least some of the burls have a first coating of diamond, cubic-BN, C3N4, a metal boride, Si3N4 or SiC or a material comprising at least two of: C, B, N, Si, and the inter-burl regions of the main body have a different coating or no coating.

15. A substrate holder according to claim 14 wherein at least one property of the first coating on the distal end surfaces of one of said burls differs from the property of the first coating on another of said burls.

16. A substrate holder according to claim 14 or claim 15 wherein at least one property of the first coating on the distal end surface of a single one of said burls differs across the distal end surface of that burl.