ILLUMINATION SYSTEM OF A MICROLITHOGRAPHIC PROJECTION EXPOSURE APPARATUS

• US 20110181850A1
• Filed: 03/09/2011
• Published: 07/28/2011
• Est. Priority Date: 09/29/2008
• Status: Active Grant

• Current Assignee: CARL Zeiss SMT GmbH (Carl-Zeiss-Stiftung)
• Original Assignee: CARL Zeiss SMT GmbH (Carl-Zeiss-Stiftung)
• Inventors: Waldis, Severin, Warm, Berndt, Bach, Florian, Werber, Armin, Benz, Daniel
• Granted Patent: US 8,797,507 B2
• Time in Patent Office: Days
• US Class Current: 355/30
• CPC Class Codes: G03F 7/70058 Mask illumination systems
• 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 7/70141 Illumination system adjustment, e.g. adjustments during exposure or alignment during assembly of illumination system
• CPC Class Codes: G03F 7/70266 Adaptive optics, e.g. deformable optical elements for wavefront control, e.g. for aberration adjustment or correction
• 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 7/70891 Temperature

Abstract

An illumination system of a microlithographic projection exposure apparatus includes a primary light source, a system pupil surface and a mirror array. The mirror array is arranged between the primary light source and the system pupil surface. The mirror array includes a plurality of adaptive mirror elements. Each mirror element includes a mirror support and a reflective coating. Each mirror element is configured to direct light produced by the primary light source towards the system pupil surface. The mirror elements can be tiltably mounted with respect to a support structure. The mirror elements include structures having a different coefficient of thermal expansion and being fixedly attached to one another. A temperature control device is configured to variably modify the temperature distribution within the structures to change the shape of the mirror elements.

Claims

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

a mirror array comprising a plurality of mirror elements, each mirror element comprising a mirror support and a reflective coating, and each mirror element being configured to direct light produced by a primary light source toward the system pupil surface; and

a temperature control device,

wherein;

each mirror element comprises structures that have different coefficients of thermal expansion;

for each mirror element, the structures are fixedly attached to each other;

the temperature control device is configured to variably modify a temperature distribution within the structures of the mirror elements to individually change a shape of each mirror element; and

the illumination system is configured to be used in a microlithographic projection exposure apparatus.

2. The illumination system of claim 1, further comprising the primary light source.

3. The illumination system of claim 1, wherein, for each mirror element, the structures comprise the mirror support and the reflective coating.

4. The illumination system of claim 1, wherein, for each mirror element, the structures comprise layers that form the reflective coating.

5. The illumination system of claim 1, wherein the temperature control device comprises members applied to the mirror supports, and the members are selected from the group consisting of heating members and cooling members.

6. The illumination system of claim 5, wherein the members comprise patterns of electrically conductive resistance wires.

7. The illumination system of claim 5, wherein the members comprise Peltier elements.

8. The illumination system of claim 1, wherein the temperature control device comprises a radiation system configured to selectively direct radiation to target areas on the reflective coatings.

9. The illumination system of claim 8, wherein the reflective coatings are absorbent for the radiation.

10. The illumination system of claim 8, wherein the radiation system comprises:

a secondary light source configured to produce a beam of the radiation; and

a spatial light modulator configured to move the beam of the radiation over the target areas

11. The illumination system of claim 8, wherein the target areas are different for different mirror elements.

12. The illumination system of claim 1, wherein the temperature control device is configured to predict a shape of the mirror elements by taking into account bending forces produced by the different coefficients of thermal expansion.

13. The illumination system of claim 1, wherein the temperature control device is configured to predict a shape of the mirror elements by taking into account bending forces produced by a non-homogenous temperature profile in the mirror elements.

14. The illumination system of claim 1, wherein the mirror elements have concave mirror surfaces, and the temperature control device is configured to modify a temperature distribution within the structures so that the mirror elements have different focal lengths in two orthogonal planes.

15. The illumination system of claim 14, wherein the light has a wavelength below 50 nm, and optical axes of the mirror elements form an angle of more than 20°

with an optical axis of a mirror which immediately precedes the mirror array in a propagation direction of the light.

16. The illumination system of claim 15, wherein an axis of symmetry is associated with the light source, and the axis of symmetry forms an angle of less than 45°

with respect to a horizontal plane.

17. The illumination system of claim 1, wherein the mirror elements comprise heat barriers having a lower coefficient of thermal conduction than materials arranged on either side of the heat barriers.

18. The illumination system of claim 1, wherein each mirror element is tiltably mounted with respect to a support structure.

19. An apparatus, comprising:

an illumination system according to claim 1; and

a projection objective,

wherein the apparatus is a microlithography projection exposure apparatus.

20. An illumination system having a pupil surface, the illumination system comprising:

a mirror array comprising a plurality of mirror elements, each mirror element comprising;

a mirror support; and

a reflective coating fixedly attached to the mirror support, the reflective coating having a different coefficient of thermal from the mirror support; and

a temperature control device configured so that, for each mirror element, the temperature control device can variably modify a temperature distribution within the mirror support and the reflective coating to individually change a shape of the mirror element,

wherein the illumination system is configured to be used in a microlithographic projection exposure apparatus.