Substrate table, lithographic apparatus and device manufacturing method
A substrate table comprising a base and a plurality of burls that project from the base, wherein an upper surface of the burls is provided with a multilayer coating.
1. A substrate table comprising:
a base;
a plurality of burls formed at atomic layer deposition (ALD)-philic sites by a multilayer coating so as to project from the base, wherein the multilayer coating includes layer to layer interfaces at which energy may dissipate; and
a plurality of ALD-phobic sites located between the ALD-philic sites and thus between the multilayer coating burls formed at the ALD-philic sites.
2. The substrate table of claim 1 , wherein the multilayer coating comprises at least one layer of Ti and at least one layer of TiN.
3. The substrate table of claim 2 , wherein an upper layer of the multilayer coating is formed from TiN.
4. The substrate table of claim 1 , wherein the multilayer coating comprises at least one layer of Cr and at least one layer of CrN.
5. The substrate table of claim 4 , wherein an upper layer of the multilayer coating is formed from CrN.
6. The substrate table of claim 1 , wherein the multilayer coating comprises 10 or more layers.
7. The substrate table of claim 1 , wherein the multilayer coating has a thickness greater than 100 nm.
8. The substrate table of claim 1 , wherein in addition to being provided on the burls, the multilayer coating is provided on regions of the substrate table that are located between the burls.
9. The substrate table of claim 1 , wherein a roughness is applied to an upper surface of the multilayer coating using plasma etching or plasma assisted chemical etching.
10. A lithographic apparatus comprising the substrate table of claim 1 .
11. A device manufacturing method comprising projecting a patterned beam of radiation onto a substrate held on a substrate table according claim 1 .
12. The substrate table of claim 1 , wherein the burls are pillars that are substantially parallel to each other and substantially perpendicular to the base.
13. A method of forming a multilayer coating on a substrate table, the method comprising:
forming atomic layer deposition (ALD)-philic sites;
forming ALD-phobic sites between the ALD-philic sites; and
using atomic layer deposition to selectively form a plurality of multilayer pillar-shaped burls on a base at the ALD-philic sites, wherein the burls comprise layers of Ti and layers of TiN or layers of Cr and layers of CrN, thereby providing the multilayer coating with layer to layer interfaces at which energy may dissipate.
14. The method of claim 13 , wherein an upper surface of the multilayer coating is etched using plasma etching to provide the upper surface with a substantially uniform roughness.
15. The method of claim 13 , wherein the burls are formed as pillars that are substantially parallel to each other and substantially perpendicular to the base.