Lithographic apparatus and device manufacturing method

• US 20050280795A1
• Filed: 08/12/2005
• Published: 12/22/2005
• Est. Priority Date: 07/16/2002
• Status: Active Grant

• Current Assignee: ASML Netherlands BV (ASML Holding NV)
• Original Assignee: ASML Netherlands BV (ASML Holding NV)
• Inventors: Van Der Laan, Hans, Van Der Werf, Jan Evert, Fockert, George Arie Jan
• Granted Patent: US 7,505,116 B2
• Time in Patent Office: Days
• US Class Current: 355/67
• CPC Class Codes: G03F 7/70233 Optical aspects of catoptric systems, i.e. comprising only reflective elements, e.g. extreme ultraviolet [EUV] projection systems
• CPC Class Codes: G03F 7/70258 Projection system adjustments, e.g. adjustments during exposure or alignment during assembly of projection system
• CPC Class Codes: G03F 7/70591 Testing optical components
• CPC Class Codes: G03F 9/7015 Reference, i.e. alignment of original or workpiece with respect to a reference not on the original or workpiece
• CPC Class Codes: G03F 9/7088 Alignment mark detection, e.g. TTR, TTL, off-axis detection, array detector, video detection

Abstract

A reflector alignment system uses an alignment beam propagating through a projection system that includes a mirror group to measure the apparent relative positions of two reference marks fixed to a reference frame on opposite sides of the projection system. Any movement of mirrors in the projection system will be detected as a shift in the apparent position of the reference marks.

Claims

1. A reflector alignment system for use in a lithographic projection apparatus including a an illuminator configured to provide a beam of radiation;

a support configured to support a patterning device, the patterning device configured to pattern the beam according to a desired pattern;

a substrate table configured to hold a substrate; and

a projection system configured to project the patterned beam onto a target portion of the substrate, the reflector alignment system being configured to direct an alignment beam of radiation through the projection system to measure apparent relative positions of a first reference mark provided in a fixed position on a patterning device side of the projection system and a second reference mark provided in a fixed position on a substrate side of the projection system.

2. A reflector alignment system according to claim 1, wherein the reflector alignment system includes reflectors from the projection system of the lithographic projection apparatus.

3. A reflector alignment system according to claim 2, further comprising first and second folding mirrors that direct the alignment beam to and from the first and second reference marks into the projection system.

4. A reflector alignment system according to claim 3, wherein the first folding mirror is an angled end of a first transparent rod.

5. A reflector alignment system according to claim 4, wherein the first reference mark comprises a first grating at an end of the first transparent rod opposite the angled end.

6. A reflector alignment system according to claim 5, further comprising a photodetector configured to detect an image of the second reference mark projected onto the first grating.

7. A reflector alignment system according to claim 6, wherein the second reference mark comprises a second grating, the second grating having a different pitch than the first grating, and a phase change between the first and second gratings caused by a relative displacement of the first and second reference marks is detected by the photodetector as a beat signal.

8. A reflector alignment system according to claim 1, wherein the second reference marks comprises a running fringe pattern formed by interference between two beams intersecting at an angle.

9. A reflector alignment system according to claim 8, further comprising a coherent light source configured to emit a beam;

a beam splitter configured to split the beam into the two beams;

a folding mirror configured to direct one of the two beams through an electro-acoustic modulator into a region of overlap with the other of the two beams at the intersecting angle.

10. A reflector alignment system according to claim 1, wherein one of the first or second reference marks comprises a retro-reflector configured to direct the alignment beam through the projection system a second time.

11. A lithographic projection apparatus, comprising:

an illumination system configured to provide a beam of radiation;

a support configured to support a patterning device, the patterning device being configured to pattern the beam of radiation according to a desired pattern;

a substrate table configured to hold a substrate;

a projection system configured to project the patterned beam onto a target portion of the substrate; and

a reflector alignment system configured to direct an alignment beam of radiation through the projection system to measure apparent relative positions of a first reference mark provided in a fixed position on a patterning device side of the projection system and a second reference mark provided in a fixed position on a substrate side of the projection system, wherein the reflector alignment system comprises reflectors which form part of the projection system.

12. A lithographic projection system according to claim 11, further comprising first and second folding mirrors that direct the alignment beam to and from the first and second reference marks into the projection system.

13. A lithographic projection system according to claim 12, wherein the first folding mirror is an angled end of a first transparent rod.

14. A lithographic projection apparatus according to claim 13, wherein the first reference mark comprises a first grating at an end of the first transparent rod opposite the angled end.

15. A lithographic projection apparatus according to claim 14, further comprising a photodetector configured to detect an image of the second reference mark projected onto the first grating.

16. A lithographic projection apparatus according to claim 15, wherein the second reference mark comprises a second grating, the second grating having a different pitch than the first grating, and a phase change between the first and second gratings caused by a relative displacement of the first and second reference marks is detected by the photodetector as a beat signal.

17. A lithographic projection apparatus according to claim 11, wherein the second reference marks comprises a running fringe pattern formed by interference between two beams intersecting at an angle.

18. A lithographic projection apparatus according to claim 17, further comprising a coherent light source configured to emit a beam;

a beam splitter configured to split the beam into the two beams;

a folding mirror configured to direct one of the two beams through an electro-acoustic modulator into a region of overlap with the other of the two beams at the intersecting angle.

19. A lithographic projection apparatus according to claim 11, wherein one of the first or second reference marks comprises a retro-reflector configured to direct the alignment beam through the projection system a second time.

20. A lithographic projection apparatus according to claim 11, wherein the beam of radiation provided by the illumination system and the alignment beam of radiation have different wavelengths.