Projection exposure system for microlithography and method of monitoring a lateral imaging stability

Patent metadata

Field	Value
Publication number	US-9235142-B2
Application number	US-97810310-A
Country	US
Kind code	B2
Filing date	Dec 23, 2010
Priority date	Jun 26, 2008
Publication date	Jan 12, 2016
Grant date	Jan 12, 2016

Abstract

A projection exposure system ( 10 ) for microlithography. The system includes projection optics ( 12 ) configured to image mask structures into a substrate plane ( 16 ), an input diffraction element ( 28 ) which is configured to convert irradiated measurement radiation ( 21 ) into at least two test waves ( 30 ) directed onto the projection optics ( 12 ) with differing propagation directions, a detection diffraction element ( 34; 28 ) which is disposed in the optical path of the test waves ( 30 ) after the latter have passed through the projection optics ( 12 ) and is configured to produce a detection beam ( 36 ) from the test waves ( 30 ) which has a mixture of radiation portions of both test waves ( 30 ), a photo detector ( 38 ) disposed in the optical path of the detection beam ( 36 ) which is configured to record the radiation intensity of the detection beam ( 36 ), time resolved, and an evaluation unit which is configured to determine the lateral imaging stability of the projection optics ( 12 ) from the radiation intensity recorded.

First claim

The invention claimed is:

1. A projection exposure system for microlithography comprising:
projection optics arranged to image mask structures into a substrate plane,
an input diffraction element configured to convert irradiated measurement radiation into at least two test waves directed onto the projection optics with differing propagation directions, such that a system pupil of the projection optics is illuminated by the at least two waves in areas which are separated locally from each other,

a detection diffraction element disposed in the optical path of the test waves after the test waves have passed through the projection optics, and configured to produce a detection beam from the test waves which has a mixture of radiation portions of the at least two test waves, and
a photo detector disposed in the optical path of the detection beam and configured to record the time-resolved radiation intensity of the detection beam, and an evaluation unit configured to determine a lateral imaging stability of the projection optics from the radiation intensity recorded, wherein the lateral imaging stability comprises an ability of the projection optics to image mask structures stably into the substrate plane with regard to a lateral shift of the image of the mask structure.

2. The projection exposure system according to claim 1 , wherein the evaluation unit is configured to determine the lateral imaging stability of the projection optics from the time resolved radiation intensity recorded at a temporal resolution of at least 10 Hz.

3. The projection exposure system according to claim 2 , wherein the at least two test waves are spatially separate from each other in at least one plane of the projection optics.

4. The projection exposure system according to claim 1 , wherein the input diffraction element is disposed on a mask side of the projection optics and the detection diffraction element is disposed on a substrate side of the projection optics.

5. The projection exposure system according to claim 1 , further comprising an illumination diffraction element disposed in the optical path of the measurement radiation upstream of the input diffraction element and is configured to convert the measurement radiation into at least two measurement radiation partial beams with differing propagation directions.

6. The projection exposure system according to claim 5 , further comprising an imaging optical element disposed between the illumination diffraction element and the input diffraction element and configured to direct the measurement radiation partial beams onto the input diffraction element.

7. The projection exposure system according to claim 5 , wherein the illumination diffraction element and the input diffraction element are configured to convert each of the at least two measurement radiation partial beams from the illumination diffraction element into at least two diffraction individual beams by diffraction on the input diffraction element, and wherein at least one of the diffraction individual beams is produced by diffracting a first of the measurement radiation partial beams overlaid by one of the diffraction individual beams produced by diffracting a second of the measurement radiation partial beams such that the overlaid diffraction individual beams together form one of the test waves.

8. The projection exposure system according to claim 1 , wherein the detection diffraction element is configured to produce, in addition to the first detection beam, at least a second detection beam and a third detection beam from the test waves, and wherein the second detection beam has at least a radiation portion of a first of the two test waves and the third detection beam has at least one radiation portion of the second of the two test waves, and the projection exposure system further comprises at least two further photo detectors arranged to record respective radiation intensities of the second detection beam and of the third detection beam.

9. The projection exposure system according to claim 1 , further comprising an exposure radiation source configured to produce radiation for imaging the mask structures into the substrate plane, and a measurement radiation source independent of the exposure radiation source configured to produce the measurement radiation.

10. The projection exposure system according to any of claim 1 , further comprising: an exposure optical path arranged to image the mask structures into the substrate plane, and a coupling mirror arranged to couple, on the mask side, the measurement radiation into the exposure optical path.

11. The projection exposure system according to claim 1 , further comprising: an exposure optical path arranged to image the mask structures into the substrate plane, and an uncoupling mirror arranged to uncouple the test waves from the exposure optical path.

12. The projection exposure system according to claim 1 , wherein the input diffraction element and the detection diffraction element are formed by a single diffraction element, and the projection exposure system further comprises a retro-reflector configured to reflect the test waves back on themselves after the test waves pass through the projection optics, such that the test waves take a second pass through the projection optics and thereafter strike the detection diffraction element.

13. The projection exposure system according to claim 1 , wherein the projection optics consists essentially of mirrors, and wherein individual regions of the surfaces of the mirrors are provided with respective reflective coatings selected in accordance with a wavelength of the measurement radiation.

14. The projection exposure system according to claim 1 , wherein the projection optics are configured to image the mask structures with light in at least the extreme-ultraviolet frequency wavelength range into the substrate plane.

15. A method for monitoring a lateral imaging stability of projection optics arranged to image mask structures into a substrate plane of a projection exposure system for microlithography, comprising:
irradiating measurement radiation onto an input diffraction element such that the measurement radiation is converted into at least two test waves with differing propagation directions, and then passing the test waves through the projection optics, such that a system pupil of the projection optics is illuminated by the at least two waves in areas which are separated locally from each other,
causing the test waves, after passing through the projection optics, to strike a detection diffraction element, and producing, by diffraction, a detection beam which has a mixture of radiation portions of the at least two test waves, and
recording the radiation intensity of the detection beam with a photo detector, time resolved, and from said recording, establishing the lateral imaging stability of the projection optics, wherein the lateral imaging stability comprises an ability of the projection optics to image mask structures stably into the substrate plane with regard to a lateral shift of the image of the mask structure.

16. The method of claim 15 , wherein establishing the lateral imaging stability of the projection optics comprises determining the lateral imaging stability of the projection optics from the time resolved radiation intensity recorded at a temporal resolution of at least 10 Hz.

17. The method of claim 16 , wherein the at least two test waves are spatially separate from each other in at least one plane of the projection optics.

18. The method of claim 15 , wherein the input diffracti

Assignees

• Manger Matthias
• Rauthe-Schoech Armin
• Mueller Ulrich
• Zeiss Carl Smt Gmbh

Inventors

• Manger Matthias
• Rauthe-Schoech Armin
• Mueller Ulrich

Classifications

• G03F7/70258 Primary

  Projection system adjustments, e.g. adjustments during exposure or alignment during assembly of projection system · CPC title

• G03F7/7085 Primary

  Detection arrangement, e.g. detectors of apparatus alignment possibly mounted on wafers, exposure dose, photo-cleaning flux, stray light, thermal load · CPC title

• G03F7/70591

  Testing optical components · CPC title

• G03F7/70191 Primary

  Optical correction elements, filters or phase plates for controlling intensity, wavelength, polarisation, phase or the like · CPC title