Method for the protection of an optical element of a lithographic apparatus and device manufacturing method

• US 20090074962A1
• Filed: 09/14/2007
• Published: 03/19/2009
• Est. Priority Date: 09/14/2007
• Status: Abandoned Application

• Current Assignee: ASML Netherlands BV (ASML Holding NV)
• Original Assignee: ASML Netherlands BV (ASML Holding NV)
• Inventors: Soer, Wouter Anthon, Wilhelmus Van Herpen, Maarten Marinus Johannes
• Application Number:
  US11/898,801
• Publication Number:
  US 20090074962A1
• Time in Patent Office: Days
• US Class Current: 427/250
• CPC Class Codes: C23C 16/0236 by etching with a reactive gas
• CPC Class Codes: C23C 16/06 characterised by the deposition of metallic material
• CPC Class Codes: G03F 7/70916 Pollution mitigation, i.e. mitigating effect of contamination or debris, e.g. foil traps
• CPC Class Codes: G03F 7/70983 Optical system protection, e.g. pellicles or removable covers for protection of mask

Abstract

A method for the protection of an optical element of a lithographic apparatus is disclosed. A deposition gas comprising SnH₄ is provided to the surface of the optical element to deposit a Sn cap layer on the surface of the optical element. In this way, a Sn cap layer is deliberately provided on the optical element, which may protect the optical element during lithographic processing from debris from a (Sn) plasma source. During or after lithographic processing, the (deteriorated) cap layer may be repaired by providing a hydrogen radical containing gas and/or a SnH4 containing gas. Additionally or alternatively, the (deteriorated) cap layer may be removed and a new cap layer provided by providing the deposition gas comprising SnH₄.

Claims

1. A method for the protection of an optical element of a lithographic apparatus, the optical element having a surface, the method comprising providing a deposition gas comprising SnH₄ to the surface of the optical element to deposit a Sn cap layer on the surface of the optical element.

2. The method of claim 1, wherein the lithographic apparatus comprises a source of radiation constructed to generate EUV radiation, and wherein the source of radiation is a Sn plasma source.

3. The method of claim 1, wherein the cap layer has a mean layer thickness in the range of 0.05-1.5 nm.

4. The method of claim 1, further comprising using the lithographic apparatus and subsequently exposing at least part of the cap layer to a repair gas comprising hydrogen radicals.

5. The method of claim 4, wherein the Sn cap layer is exposed to the repair gas until the cap layer has a mean layer thickness selected from the range of 0.05-1 nm.

6. The method of claim 1, further comprising using the lithographic apparatus and subsequently exposing at least part of the cap layer to a repair gas comprising SnH₄.

7. The method of claim 6, wherein the Sn cap layer is exposed to the repair gas until the cap layer has a mean layer thickness selected from the range of 0.05-1.5 nm.

8. The method of claim 1, further comprising using the lithographic apparatus and subsequently exposing at least part of the cap layer to a cleaning gas, removing at least part of the Sn cap layer using the cleaning gas, and providing the deposition gas comprising SnH₄ to the surface to deposit a fresh Sn cap layer on the surface of the optical element.

9. The method of claim 8, wherein substantially the complete Sn cap layer is removed by the cleaning gas and wherein the cleaning gas comprises a halogen.

10. The method of claim 1, wherein the Sn cap layer comprises at least 95 wt. % Sn.

11. The method of claim 1, wherein the optical element is a collector mirror and wherein the surface is a reflective surface of the collector mirror.

12. The method of claim 1, wherein providing the deposition gas comprising SnH₄ to the surface of the optical element to deposit the Sn cap layer on the surface of the optical element is an in situ lithographic apparatus process.

13. The method of claim 1, comprising

a. use of the lithographic apparatus in a device manufacturing process (a);

b. a repair process (b), wherein at least part of the cap layer after use of the lithographic apparatus is exposed to a repair gas comprising hydrogen radicals or SnH₄;

wherein processes (a) and (b) are repeated a plurality of times.

14. The method of claim 1, comprising

a. use of the lithographic apparatus in a device manufacturing process (a);

b. a repair process (b), wherein at least part of the cap layer after use of the lithographic apparatus is exposed to a repair gas comprising hydrogen radicals or SnH₄;

c. a cleaning process (c), comprising exposing at least part of the cap layer to a cleaning gas, removing at least part of the Sn cap layer by the cleaning gas; and

d. after cleaning process (c), a deposition process (d) comprising providing a deposition gas comprising SnH₄ to the surface of the optical element to deposit a fresh Sn cap layer on the surface of the optical element;

wherein processes (a) and (b) are repeated a plurality of times before performing processes (c) and (d).

15. A lithographic apparatus comprising an optical element, the optical element having a surface, a gas source configured to supply a gas comprising SnH₄ and to direct a flow of the gas to the surface the of optical element and a cleaning gas source configured to supply a cleaning gas comprising a halogen and to direct a flow of cleaning gas to a Sn cap layer on the surface of the optical element.

16. The lithographic apparatus of claim 15, wherein the Sn cap layer is a dynamic cap layer.

17. A device manufacturing method using a lithographic apparatus, wherein the lithographic apparatus comprises an optical element having a surface with a Sn cap layer.

18. The device manufacturing method of claim 17, further comprising using the lithographic apparatus and subsequently exposing at least part of the cap layer to a repair gas comprising hydrogen radicals.

19. The device manufacturing method of claim 17, further comprising using the lithographic apparatus and subsequently exposing at least part of the cap layer to a repair gas comprising SnH₄.

20. The device manufacturing method of claim 17, further comprising using the lithographic apparatus and subsequently exposing at least part of the cap layer to a cleaning gas, removing at least part of the Sn cap layer using the cleaning gas, and providing a deposition gas comprising SnH₄ to the surface to deposit a fresh Sn cap layer on the surface of the optical element.

21. The device manufacturing method of claim 17, wherein the Sn cap layer is provided by providing a deposition gas comprising SnH₄ to the surface to deposit the Sn cap layer on the surface of the optical element in situ in the lithographic apparatus.

22. The device manufacturing method of claim 17, wherein the optical element is a collector mirror and wherein the surface is a reflective surface of the collector mirror.