ILLUMINATION SYSTEM OF A MICROLITHOGRAPHIC PROJECTION EXPOSURE APPARATUS

• US 20150146183A1
• Filed: 11/17/2014
• Published: 05/28/2015
• Est. Priority Date: 11/22/2013
• Status: Active Grant

• Current Assignee: CARL Zeiss SMT GmbH (Carl-Zeiss-Stiftung)
• Original Assignee: CARL Zeiss SMT GmbH (Carl-Zeiss-Stiftung)
• Inventors: Deguenther, Markus, Davydenko, Vladimir, Korb, Thomas, Schlesener, Frank, Hilt, Stefanie, Hoegele, Wolfgang
• Granted Patent: US 9,500,954 B2
• Time in Patent Office: Days
• US Class Current: 355/67
• CPC Class Codes: G02B 26/0833 the reflecting element being a micromechanical device, e.g. a MEMS mirror, DMD G02B26/0825 takes precedence; micromechanical devices in general B81B
• CPC Class Codes: G03F 7/70058 Mask illumination systems
• CPC Class Codes: G03F 7/70066 Size and form of the illuminated area in the mask plane, e.g. reticle masking blades or blinds
• CPC Class Codes: G03F 7/70075 Homogenization of illumination intensity in the mask plane by using an integrator, e.g. fly's eye lens, facet mirror or glass rod, by using a diffusing optical element or by beam deflection
• CPC Class Codes: G03F 7/70116 Off-axis setting using a programmable means, e.g. liquid crystal display [LCD], digital micromirror device [DMD] or pupil facets
• CPC Class Codes: G03F 7/70191 Optical correction elements, filters or phase plates for controlling intensity, wavelength, polarisation, phase or the like
• CPC Class Codes: G03F 7/70425 Imaging strategies, e.g. for increasing throughput or resolution, printing product fields larger than the image field or compensating lithography- or non-lithography errors, e.g. proximity correction, mix-and-match, stitching or double patterning

Abstract

An illumination system of a microlithographic projection exposure apparatus includes an optical integrator having a plurality of light entrance facets each being associated with a secondary light source. A spatial light modulator has a light exit surface and transmit or to reflect impinging projection light in a spatially resolved manner. A pupil forming unit directs projection light on the spatial light modulator. An objective images the light exit surface of the spatial light modulator onto the light entrance facets of the optical integrator. The light exit surface of the optical light modulator includes groups of object areas being separated by areas that are not imaged on the light entrance facets. The objective combines images of the object areas so that the images of the object areas abut on the optical integrator.

Claims

1. An illumination system having a pupil plane, the illumination system comprising:

an optical integrator configured so that, during use of the illumination system, the optical integrator produces a plurality of secondary light sources in the pupil plane, the optical integrator comprising a plurality of light entrance facets, each light entrance facet being associated with a secondary light source;

a spatial light modulator having a light exit surface, the spatial light modulator configured so that, during use of the illumination system, the spatial light modulator transmits or reflects impinging projection light in a spatially resolved manner;

a pupil forming unit configured so that, during use of the illumination system, the pupil forming unit directs projection light onto the spatial light modulator;

an objective configured so that, during use of the illumination system, the objective images the light exit surface of the spatial light modulator onto the light entrance facets of the optical integrator; and

a control unit configured so that, during use of the illumination system, the control unit controls the pupil forming unit and the spatial light modulator,

wherein;

the light exit surface of the optical light modulator comprises groups of object areas which are separated by areas that are not imaged on the light entrance facets during use of the illumination system;

the objective is configured so that, during use of the illumination system, the objective combines images of the object areas so that the images of the object areas abut on the optical integrator; and

the illumination system is a microlithographic illumination system.

2. The illumination system of claim 1, wherein the objective comprises:

a first array of first optical elements, each first optical element configured so that, during use of the illumination system, the first optical element forms a magnified image of one of the groups in an intermediate image plane; and

imaging optics configured so that, during use of the illumination optics, the imaging optics image the intermediate image plane onto the light entrance facets.

3. The illumination system of claim 2, wherein the objective comprises a second array of second optical elements arranged in the intermediate image plane.

4. The illumination system of claim 3, wherein each second optical element is associated with one of the first optical elements in a one to one correspondence so that, during use of the illumination system, each second optical element receives projection light only from the associated one of the first optical elements.

5. The illumination system of claim 1, wherein the pupil forming unit comprises a beam deflection array of reflective or transparent beam deflection elements, and each beam deflection element is configured so that, during use of the illumination system, the beam deflection element illuminates a spot on the spatial light modulator at a position that is variable by changing a deflection angle produced by the first beam deflection element.

6. The illumination system of claim 1, wherein:

the spatial light modulator comprises a beam deflection array of reflective or transparent beam deflection elements;

each beam deflection element configurable in an on state and in an off state;

for each beam deflection element, the beam deflection element is configured so that during use of the illumination system;

when in its on state, the beam deflection element directs impinging projection light toward the optical integrator; and

when its off state, the beam deflection element directs impinging projection light elsewhere.

7. The illumination system of claim 6, wherein:

the beam deflection elements comprise mirrors; and

during use of the illumination system, projection light propagating from the pupil forming unit to the spatial light modulator passes at least through a portion of the objective.

8. The illumination system of claim 7, wherein:

the objective comprises;

a first array of first optical elements, each first optical element configured so that, during use of the illumination system, the first optical element forms a magnified image of one of the groups in an intermediate image plane;

imaging optics configured to image the intermediate image plane onto the light entrance facets;

a second array of second optical elements arranged in the intermediate image plane; and

during use of the illumination system, projection light propagating from the pupil forming unit to the spatial light modulator impinges on the first array of first optical elements and on the second array of second optical elements before it impinges on the mirrors.

9. The illumination system of claim 7, wherein:

the mirrors comprise planar mirrors having a mirror normal that forms, when the mirror is in its on state, a non-zero degree angle relative to a direction which is parallel to an optical axis of the objective; and

the objective comprises a light tilting optical element that is configured to tilt impinging projection light rays by the non-zero angle.

10. The illumination system of claim 9, wherein:

the objective comprises;

a first array of first optical elements, each first optical element configured so that, during use of the illumination system, the first optical element forms a magnified image of one of the groups in an intermediate image plane; and

imaging optics configured so that, during use of the illumination optics, the imaging optics image the intermediate image plane onto the light entrance facets; and

the light tiling element is arranged between the mirrors and the first optical elements.

11. The illumination system of claim 9, wherein the light tilting element comprises a transparent refractive wedge.

12. The illumination system of claim 11, wherein the wedge is a Fresnel wedge comprising a plurality of individual wedge elements.

13. The illumination system of claim 7, wherein:

the objective has a pupil plane; and

the pupil forming unit is configured so that, during use of the illumination system, the pupil forming unit produces an angular light distribution in the pupil plane of the objective in an area so that projection light, after reflection from the mirrors, cannot pass through the area again irrespective of whether the mirrors are in the on or in the off state.

14. The illumination system of claim 13, wherein the area is located on a beam deviating surface configured to so that, during use of the illumination system, the beam deviating surface couples the projection light emerging from the pupil forming unit into a light path of the objective.

15. The illumination system of claim 7, wherein the objective has an optical surface configured so that, during use of the illumination system, the optical surface reflects projection light propagating from the pupil forming unit towards the mirror, and transmits projection light after the reflection light reflects from the mirrors but before the projection light impinges on the light entrance facets.

16. The illumination system of claim 15, wherein the optical surface is configured to reflect the projection light as a result of total internal reflection during use of the illumination system.

17. The illumination system of claim 16, wherein the optical surface comprises a prism surface.

18. The illumination system of claim 1, wherein the control unit is configured so that, during use of the illumination system, the control unit controls the spatial light modulator so that along a scan direction a length of an image formed on the mask from a light pattern in one of the object areas gradually increases at a beginning of a scan cycle and gradually decreases at the end of the scan cycle.

19. The illumination system of claim 18, wherein:

the spatial light modulator comprises a beam deflection array of reflective or transparent beam deflection elements;

each beam deflection element configurable in an on state and in an off state;

for each beam deflection element, the beam deflection element is configured so that during use of the illumination system;

when in its on state, the beam deflection element directs impinging projection light toward the optical integrator; and

when its off state, the beam deflection element directs impinging projection light elsewhere;

the control unit is configured so that, during use of the illumination system, the control unit controls the spatial light modulator so that rows of adjacent second beam deflection elements are simultaneously brought from the off state into the on state, and vice versa, during the scan cycle.

20. An apparatus, comprising:

an illumination system according to claim 1; and

a projection objective,

wherein the apparatus is a microlithographic projection exposure apparatus.

21. A method of using an apparatus comprising an illumination system and a projection objective, the method comprising:

using the illumination system to illuminate at least some structures of a mask; and

using the projection objective to image at least a portion of the illuminated structures onto a light-sensitive material,

wherein the illumination system is an illumination system according to claim 1.

22. A method of operating an illumination system of a microlithographic projection exposure apparatus comprising a spatial light modulator having a light exit surface comprising first areas separated by second areas, comprising the following steps:

imaging the first areas, but not the second areas, on a final image plane so that images of the first areas abut in the final image plane.

23. An optical system having a final image plane, the optical system comprising:

a spatial light modulator having a light exit surface, the spatial light modulator configured so that, during use of the optical system, the spatial light modulator modulates an optical property of light in a spatially resolved manner, the light exit surface comprising first and second areas, the second areas being separate the first areas, the second areas not being imaged on the final image plane during use of the optical system;

an objective configured so that, during use of the optical system, the objective images the light exit surface of the spatial light modulator onto the final image plane,

wherein the objective is configured so that, during use of the optical system, the objective combines images of the first areas so that these images abut in the final image plane.