Wafer chuck for EUV lithography

• US 8,564,925 B2
• Filed: 06/17/2011
• Issued: 10/22/2013
• Est. Priority Date: 12/19/2008
• Status: Active Grant

• Current Assignee: CARL Zeiss SMT GmbH (Carl-Zeiss-Stiftung)
• Original Assignee: CARL Zeiss SMT GmbH (Carl-Zeiss-Stiftung)
• Inventors: Six, Stephan
• Primary Examiner(s): Leja, Ronald W
• Application Number:
  US13/163,100
• Publication Number:
  US 20110310524A1
• Time in Patent Office: 858 Days
• Field of Search: 361/234
• US Class Current: 361/234
• CPC Class Codes: G03F 7/70708 being electrostatic; Electrostatically deformable vacuum chucks
• CPC Class Codes: G03F 7/70783 Handling stress or warp of chucks, masks or workpieces, e.g. to compensate for imaging errors or considerations related to warpage of masks or workpieces due to their own weight

Abstract

A wafer chuck (1b) having a substrate (2) and having, applied to the substrate (2), an electrically conductive coating (8) for fixing a wafer (6) by electrostatic attraction and preferably having a reflective coating (10) applied to the substrate (2). The coating (8; 10) has at least a first layer (3; 11) under compressive stress and at least a second layer (7; 12) under tensile stress for compensating for the compressive stress of the first layer (3; 11) in order to keep deformation of the wafer chuck (1b) by the coating (8, 10) as low as possible.

Claims

1. A wafer chuck comprising:

a substrate and

applied to the substrate, an electrically conductive coating for fixing a wafer by electrostatic attraction, wherein;

the electrically conductive coating comprises at least a first layer under compressive stress, and at least a second layer under tensile stress compensating for the compressive stress of the first layer, and

the electrically conductive coating has a total thickness of less than 300 nm.

2. The wafer chuck according to claim 1, wherein the material of the first layer of the electrically conductive coating comprises:

nitrides, carbides and silicides.

3. The wafer chuck according to claim 2, wherein the material of the first layer of the electrically conductive coating is selected from the group consisting of:

titanium nitride (TiN), chromium nitride (CrN), molybdenum silicide (MoSi₂), silicon carbide (SiC) and silicon nitride (Si₃N₄).

4. The wafer chuck according to claim 1, wherein the second layer of the electrically conductive coating has a tensile stress of from 100 MPa to 1600 MPa.

5. The wafer chuck according to claim 4, wherein the second layer of the electrically conductive coating has a tensile stress of from 800 MPa to 1300 MPa.

6. The wafer chuck according to claim 1, wherein the second layer of the electrically conductive coating is composed of a metal.

7. The wafer chuck according to claim 6, wherein the second layer of the electrically conductive coating is composed of chromium.

8. The wafer chuck according to claim 1, wherein the second layer of the electrically conductive coating is formed from a material having a higher electrical conductivity than the material of the first layer.

9. The wafer chuck according to claim 1, wherein the first layer of the electrically conductive coating has a thickness of less than 200 nm.

10. The wafer chuck according to claim 9, wherein the first layer of the electrically conductive coating has a thickness of less than 50 nm.

11. The wafer chuck according to claim 1, wherein the substrate is composed of a non-conductive material.

12. The wafer chuck according to claim 11, wherein the substrate is composed of Zerodur.

13. The wafer chuck according to claim 1, wherein the first layer of the electically conductive coating is applied to the second layer.

14. The wafer chuck according to claim 1, wherein the first layer of the electrically conductive coating is formed by sputtering and the second layer is formed by thermal evaporation.

15. The wafer chuck according to claim 14, wherein the first layer of the electrically conductive coating is formed by sputtering with ion assistance.

16. The wafer chuck according to claim 1, wherein the electically conductive coating is formed from at least one of metallic layer materials and dielectric layer materials deposited with ion assistance.

17. The wafer chuck according to claim 1, wherein the electrically conductive coating has a water-impermeable sealing layer.

18. The wafer chuck according to claim 1, wherein the second layer of the electrically conductive coating is in a form such as to compensate for a change in stress in the first layer of the electrically conductive coating caused by the loss of water in a vacuum environment.

19. The wafer chuck according to claim 1, further comprising a reflective coating applied to a side surface of the substrate, wherein:

the electrically conductive coating is applied to a top surface of the substrate, and

the reflective coating comprises at least a first layer under compressive stress, and at least a second layer under tensile stress compensating for the compressive stress of the first layer.

20. The wafer chuck according to claim 19, wherein the reflective coating comprises at least one metallic layer material.

21. The wafer chuck according to claim 20, wherein the at least one metallic layer material is aluminium (Al) or silver (Ag).

22. The wafer chuck according to claim 19, wherein the reflective coating has at least one layer material deposited which is selected from the group comprising:

titanium dioxide (TiO₂), silicon dioxide (SiO₂), hafnium dioxide (HfO₂) and zirconium dioxide (ZrO₂).

23. The wafer chuck according to claim 22, wherein the at least one layer material is deposited with ion assistance.

24. The wafer chuck according to claim 19, wherein the reflective coating has a total thickness of less than 400 nm.

25. The wafer chuck according to claim 19, wherein the first layer of the reflective coating is applied to the second layer.

26. The wafer chuck according to claim 19, wherein the reflective coating is formed from at least one of metallic layer materials and dielectric layer materials deposited with ion assistance.

27. The wafer chuck according to claim 19, wherein the reflective coating comprises a water-impermeable sealing layer.

28. The wafer chuck according to claim 19, wherein the second layer of the reflective coating is in a form such as to compensate for a change in stress in the first layer of the reflective coating caused by the loss of water in a vacuum environment.