WAFER CHUCK FOR EUV LITHOGRAPHY

• US 20110310524A1
• Filed: 06/17/2011
• Published: 12/22/2011
• 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
• Granted Patent: US 8,564,925 B2
• Time in Patent Office: Days
• 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 having a substrate and having, applied to the substrate, an electrically conductive coating for fixing a wafer by electrostatic attraction and preferably having a reflective coating applied to the substrate, characterised in that

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

2. The wafer chuck according to claim 1, wherein the material of the first layer of the electrically conductive coating is selected from the group comprising:

nitrides, carbides and silicides.

3. The wafer chuck according to claim 1, wherein the material of the first layer of the electrically conductive coating is selected from the group comprising:

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 (8) has a tensile stress of from 100 MPa to 1600 MPa, preferably from 800 MPa to 1300 MPa.

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

6. 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.

7. The wafer chuck according to claim 1, wherein the first layer of the electrically conductive coating has a thickness of less than 200 nm, preferably less than 100 nm, especially less than 50 nm.

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

9. The wafer chuck according to claim 1, wherein the first layer is applied to the second layer.

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

11. The wafer chuck according to claim 1, wherein the coating is formed from metallic layer materials and/or from dielectric layer materials deposited with ion assistance.

12. The wafer chuck according to claim 1, wherein the reflective coating has at least one metallic layer material, especially aluminium (Al) or silver (Ag).

13. The wafer chuck according to claim 1, wherein the reflective coating has at least one layer material deposited preferably with ion assistance which is selected from the group comprising:

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

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

15. The wafer chuck according to claim 1, wherein the electrically conductive coating has a total thickness of less than 300 nm and the reflective coating has a total thickness of less than 400 nm.

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