Method for machining a workpiece in the production of an optical element

Patent metadata

Field	Value
Publication number	US-11980990-B2
Application number	US-202016810189-A
Country	US
Kind code	B2
Filing date	Mar 5, 2020
Priority date	Sep 12, 2017
Publication date	May 14, 2024
Grant date	May 14, 2024

Abstract

A method for the zonal polishing of a workpiece includes using a polishing tool to guide a structured polishing pad over the surface of workpiece to remove material from the workpiece. A structured polishing pad includes a structuring adapted to the movement of a polishing tool.

First claim

What is claimed is:

1. A method, comprising:
using a polishing tool to move a structured polishing pad over a surface of a workpiece to remove material from the workpiece, thereby zonally polishing the workpiece to provide a polished surface of the workpiece;
after zonally polishing the workpiece, smoothing the polished surface of the workpiece to provide a smoothed surface of the workpiece; and
disposing a reflecting layer on the smoothed surface of the workpiece.

2. The method of claim 1 , further comprising rotating the structured polishing pad over the surface of the workpiece.

3. The method of claim 2 , further comprising eccentrically moving the structured polishing pad over the surface of the workpiece.

4. The method of claim 1 , further comprising eccentrically moving the structured polishing pad over the surface of the workpiece.

5. The method of claim 1 , wherein disposing the reflecting layer on the smoothed surface of the workpiece provides an optical element which comprises the reflective surface supported by the workpiece.

6. The method of claim 1 , further comprising, before zonally polishing the workpiece, zonally lapping the workpiece.

7. The method of claim 6 , wherein zonal lapping comprises using an effective area of the tool that is less than 20% of an area of the surface of the workpiece that is to be processed.

8. The method of claim 1 , wherein zonal polishing comprises using an effective area of the tool that is less than 20% of an area of the surface of the workpiece that is to be processed.

9. The method of claim 1 , wherein a rate of material removal from the workpiece is approximately constant.

10. The method of claim 1 , wherein the reflecting layer is configured to reflect EUV radiation.

11. The method of claim 1 , wherein the reflecting layer is configured to reflect UV light.

12. The method of claim 1 , wherein the reflecting layer comprises a plurality of layers of different materials.

13. The method of claim 1 , wherein the polishing pad comprises a primary structure and a secondary structure, the primary structure comprises a spiral shape comprising a plurality of spiral arms, and the secondary structure comprises rotationally asymmetrical channels.

14. The method of claim 1 , further comprising, before using the polishing tool:
selecting an intended movement of the polishing tool over the surface of the workpiece; and
selecting the polishing tool based on the intended movement of the polishing pad over the workpiece.

15. The method of claim 1 , wherein the polishing tool is moved periodically moved over the surface of the workpiece.

Assignees

• Zeiss Carl Smt Gmbh

Inventors

• Matena Manfred
• Stickel Franz-Josef
• Saitner Marc
• Fichtl Robert
• Brust Hans-Peter

Classifications

• B24B13/01 Primary

  Specific tools, e.g. bowl-like; Production, dressing or fastening of these tools · CPC title

• B24B37/26

  characterised by the shape of the lapping pad surface, e.g. grooved · CPC title

• B24D13/147

  comprising assemblies of felted or spongy material; comprising pads surrounded by a flexible material · CPC title

• B24D2203/00

  Tool surfaces formed with a pattern · CPC title

• B24D11/04 Primary

  Zonally-graded surfaces · CPC title