Optical system for increasing illumination efficiency of a patterning device

• US 20070241292A1
• Filed: 04/13/2006
• Published: 10/18/2007
• Est. Priority Date: 04/13/2006
• Status: Active Grant

• Current Assignee: ASML Holding NV
• Original Assignee: ASML Holding NV
• Inventors: Smirnov, Stanislav
• Granted Patent: US 7,839,487 B2
• Time in Patent Office: Days
• US Class Current: 250/548
• CPC Class Codes: G03F 7/70083 Non-homogeneous intensity distribution in the mask plane
• CPC Class Codes: G03F 7/70291 Addressable masks, e.g. spatial light modulators [SLMs], digital micro-mirror devices [DMDs] or liquid crystal display [LCD] patterning devices
• CPC Class Codes: G03F 7/70791 Large workpieces, e.g. glass substrates for flat panel displays or solar panels

Abstract

A system and method form illumination that efficiently illuminates target areas of an object. For example, target areas can be transmission areas of a diaphragm and/or active areas of a patterning device. A plurality of beams formed by a field defining element are directed onto respective entrance faces of a plurality of rods using a relay of first and second lens arrays. The rods process the beams to form illumination that impinges substantially only within a boundary of the target areas, e.g., the transmission areas and/or the active areas. The rods are arranged in number, configuration, and cross-sectional shape corresponding to a number, configuration, and a cross-sectional shape of the target areas, e.g., the transmission areas and/or the active areas. Thus, substantially all the illumination falls within the boundary of the target areas, increasing illumination efficiency.

Claims

1. An optical system, comprising:

an optical element that receives a beam and generates a plurality of beams therefrom;

a relay of first and second lens arrays, each lens in the first lens array receiving a respective portion of the plurality of beams and directing the respective portion onto a corresponding lens in the second lens array;

a plurality of rods, which correspond in number and arrangement to the lenses in the second lens array, each of the rods receiving a beam from a corresponding lens in the second lens array; and

an object including a plurality of target areas corresponding in number and shape to a number and a cross-sectional shape of the rods, each of the target areas receiving a beam from a corresponding one of the rods substantially within a boundary of the target area.

2. The optical system of claim 1, wherein the optical element comprises a diffractive or refractive optical element.

3. The optical system of claim 1, wherein the first and second lens arrays comprise fly'"'"'s eye lens arrays.

4. The optical system of claim 1, wherein each rod comprises a glass rod.

5. The optical system of claim 1, wherein each rod comprises a hollow rod having reflective interior walls.

6. The optical system of claim 1, wherein the relay is configured to demagnify an image between the optical element and the plurality of rods.

7. The optical system of claim 1, wherein:

the object comprises a diaphragm; and

the target areas comprise transmission areas of the diaphragm.

8. The optical system of claim 7, further comprising:

a patterning device including active areas corresponding in number and shape to the transmission areas of the diaphragm; and

a second relay that directs light from the transmission areas of the diaphragm onto corresponding ones of the active areas of the patterning device,

wherein the second relay directs light substantially within respective boundaries of the corresponding ones of the active areas.

9. The optical system of claim 1, wherein:

the object comprises a patterning device; and

the target areas comprise active areas of the patterning device.

10. The optical system of claim 9, wherein:

the patterning device comprises an array of individually controllable elements; and

each of the individually controllable elements includes one of the active areas.

11. The optical system of claim 1, further comprising:

a. second relay located between the plurality of rods and the patterning device.

12. The optical system of claim 1, wherein the relay is configured to maintain double telecentricity of the plurality of beams.

13. The optical system of claim 1, wherein the first and second lens arrays comprise microlens arrays.

14. The optical system of claim 1, wherein substantially an entire entrance face of each of the rods is illuminated with the beam from the corresponding lens in the second lens array.

15. The optical system of claim 1, wherein the relay creates an image of the optical element on or close to a plane of entrance faces of the plurality of rods.

16. The optical system of claim 1, wherein an entrance face of each rod in the plurality of rods is partially illuminated with the beam from the corresponding lens in the second lens array.

17. A lithography system, comprising:

a radiation source producing a beam of radiation;

an illumination system that processes the beam to produce a plurality of beams of radiation, the illumination system comprising,

a pupil defining element,

a condenser lens,

a field defining element,

a first relay comprising first and second lens arrays,

a plurality of rods,

a diaphragm having transmission areas, and

a second relay;

a patterning device that patterns the plurality of beams of radiation; and

a projection system that projects the patterned beams onto a substrate.

18. The lithography system of claim 17, wherein the plurality of rods correspond in number and arrangement to a number and arrangement of lenses in the second lens array.

19. The lithography system of claim 17, wherein the transmission areas correspond in number, arrangement, and shape to a number, arrangement, and cross-sectional shape of rods in the plurality of rods.

20. The lithography system of claim 17, wherein the patterning device comprises an array of individually controllable elements each having an active area corresponding in number, arrangement, and shape to a number, arrangement, and shape of the transmission areas.

21. The lithography system of claim 17, wherein the plurality of rods comprise glass rods or hollow rods.

22. The lithography system of claim 17, wherein the first and second lens arrays comprise first and second fly'"'"'s eye lens arrays or first and second microlens arrays.

23. A method, comprising:

generating a plurality of beams of radiation using an optical element;

receiving the beams on respective lenses in a first lens array;

using the first lens array to direct the beams onto corresponding lenses in a second lens array;

using the second lens array to direct the beams onto corresponding rods in a plurality of rods, the plurality of rods corresponding in number and arrangement to lenses in the second lens array; and

using the plurality of rods to direct the beams substantially within a boundary of corresponding target areas of an object, the object including a plurality of the target areas, the plurality of the target areas corresponding in number and shape to a number and a cross-sectional shape of the rods in the plurality of rods.

24. The method of claim 23, further comprising using transmission areas of a diaphragm as the target areas of the object.

25. The method of claim 24, further comprising:

directing the beams from the transmission areas onto active areas of a patterning device using a relay system;

patterning the beams using the active areas of the patterning device; and

projecting the patterned beams onto a substrate.

26. The method of claim 23, further comprising using a semiconductor wafer or a flat panel glass substrate as the substrate.

27. The method of claim 23, further comprising using active areas of a patterning device as the target areas of the object.