Off-Axis Catadioptric Projection Optical System for Lithography

• US 20090153954A1
• Filed: 02/20/2009
• Published: 06/18/2009
• Est. Priority Date: 07/30/2004
• Status: Active Grant

• Current Assignee: ASML Holding NV
• Original Assignee: ASML Holding NV
• Inventors: Oskotsky, Mark, SMIRNOV, Stanislav
• Granted Patent: US 7,834,979 B2
• Time in Patent Office: Days
• US Class Current: 359/365
• CPC Class Codes: G02B 17/0812 off-axis or unobscured systems in which all of the mirrors share a common axis of rotational symmetry
• CPC Class Codes: G03B 27/54 Lamp housings; Illuminating means
• CPC Class Codes: G03F 7/70225 Optical aspects of catadioptric systems, i.e. comprising reflective and refractive elements

Abstract

The present invention is directed to off-axis catadioptric projection optical systems for use in lithography tools for processing modulated light used to form an image on a substrate, such as a semiconductor wafer or flat panel display. In one embodiment the optical system includes an off-axis mirror segment, a fold mirror, a relay, an aperture stop and a refractive lens group. Modulated light is transmitted through the system to form an image on a substrate. In a second embodiment the projection system includes an off-axis mirror segment, an aperture stop and a refractive lens group. In a third embodiment the projection system includes an off-axis mirror segment, a negative refractive lens group, a concave mirror, a relay, an aperture stop, and a refractive lens group. A method to produce a device using a lithographic apparatus including a projection system with an off-axis mirror segment as the first element in a projection optics system is also provided.

Claims

1. A system comprising:

an off-axis mirror segment configured to receive modulated light, an axis of the off-axis mirror segment differing from an axis of a substrate configured to receive an image from a projection system having multiple mirror segments, the off-axis mirror segment being the first mirror segment within the projection system;

an aperture stop configured to receive the modulated light from the off-axis mirror segment; and

a refractive lens group configured to focuse the modulated light onto the substrate.

2. The system of claim 1, further comprising a pattern generating device configured to provide the modulated light for use in forming the image on the substrate.

3. The system of claim 2, wherein the pattern generating device is a spatial light modulator.

4. The system of claim 1, wherein the off-axis mirror segment is concave.

5. The system of claim 1, wherein the off-axis mirror segment provides field curvature correction.

6. The system of claim 1, wherein the substrate is a semiconductor wafer or flat panel display.

7. An optical system, comprising:

an off-axis mirror segment configured to receive modulated light, an axis of the off-axis mirror segment differing from an axis of a substrate, the off-axis mirror segment is a first mirror segment within the optical system;

a fold mirror configured to receive the modulated light from the off-axis mirror segment;

a relay configured to receive the modulated light from the fold mirror and to focus the modulated light;

an aperture stop configured to receive the modulated light from the relay; and

a refractive lens group configured to focus the modulated light onto the substrate.

8. The optical system of claim 7, further comprising a pattern generating device configured to provide the modulated light for use in forming an image on the substrate.

9. The optical system of claim 8, wherein the pattern generating device is a spatial light modulator.

10. The optical system of claim 7, wherein the off-axis mirror segment is concave.

11. The optical system of claim 7, wherein the off-axis mirror segment provides field curvature correction.

12. An optical system, comprising:

an off-axis mirror segment configured to receive modulated light, an axis of the off-axis mirror segment differing from an axis of the substrate, the off-axis mirror segment being a first mirror within the optical system;

a concave mirror configured to receives modulated light from the off-axis mirror segment;

a negative refractive lens group positioned between the off-axis mirror segment and the concave mirror;

a relay configured to receives light from the concave mirror configured to has passed through the refractive lens group and configured to focuses the modulated light;

an aperture stop configured to receives the modulated light from the relay; and

a refractive lens group configured to focuses the modulated light onto the substrate.

13. The optical system of claim 12, further comprising a pattern generating device configured to provides the modulated light for use in forming an image on the substrate.

14. The optical system of claim 13, wherein the pattern generating device is a spatial light modulator.

15. The optical system of claim 12, wherein the off-axis mirror segment is concave.

16. The optical system of claim 12, wherein the off-axis mirror segment provides field curvature correction.

17. The optical system of claim 12, wherein the negative refractive lens group provides chromatic aberration reduction.

18. The optical system of claim 12, wherein the substrate is a semiconductor wafer or a flat panel display.

19. A lithographic apparatus, comprising:

an illumination system configured to supply a beam of radiation;

a pattern generator configured to pattern the beam; and

a projection system configured to project the patterned beam along a predetermined beam path onto a substrate, wherein the projection system comprises an off-axis mirror segment configured to receive the patterned beam from the pattern generator, wherein an axis of the off-axis mirror segment differs from an axis of the substrate, wherein the off-axis mirror segment is the first mirror segment within the projection system, wherein the projection system includes at most three mirrors.

20. A method comprising:

transmitting a patterned beam parallel to an axis of an off-axis mirror segment differing from an axis of a substrate that receives an image from a projection system with the off axis mirror segment, the off-axis mirror segment being a first mirror segment within the projection system;

reflecting the patterned beam with the off-axis mirror segment;

focusing the reflected patterned beam; and

imaging the reflected patterned beam onto the substrate.

21. The method of claim 20, wherein the imaging comprises imaging the reflected patterned beam onto a substrate to create an integrated circuit.

22. The method of claim 20, wherein the imaging comprises imaging the reflected patterned beam onto the substrate to create a flat panel display.