Measuring system for measuring an imaging quality of an EUV lens

Patent metadata

Field	Value
Publication number	US-9494483-B2
Application number	US-201414494144-A
Country	US
Kind code	B2
Filing date	Sep 23, 2014
Priority date	Mar 23, 2012
Publication date	Nov 15, 2016
Grant date	Nov 15, 2016

Abstract

A measuring system ( 10 ) for measuring an imaging quality of an EUV lens ( 30 ) includes a diffractive test structure ( 26 ), a measurement light radiating device ( 16 ) which is configured to radiate measurement light ( 21 ) in the EUV wavelength range onto the test structure, a variation device ( 28 ) for varying at least one image-determining parameter of an imaging of the test structure that is effected by a lens, a detector ( 14 ) for recording an image stack including a plurality of images generated with different image-determining parameters being set, and an evaluation device ( 15 ) which is configured to determine the imaging quality of the lens from the image stack.

First claim

The invention claimed is:

1. A measuring system for measuring an imaging quality of an extreme ultraviolet (EUV) lens comprising:
a diffractive test structure contained in an absorption layer applied on a multilayer arrangement,
a measurement light radiating device configured to radiate measurement light in the EUV wavelength range onto the test structure,
a variation device configured to vary at least one image-determining parameter of an imaging of the test structure effected by the lens,
a detector configured to record an image stack comprising a plurality of images generated with mutually differing image-determining parameters varied by the variation device, and
an evaluation device configured to determine the imaging quality of the lens from the image stack.

2. The measuring system according to claim 1 ,
wherein the test structure is part of a test mask having a reflective effect with respect to the measurement light and the test mask comprises the multilayer arrangement.

3. The measuring system according to claim 1 ,
wherein the diffractive test structure is part of a test mask and the measurement light radiating device is configured to radiate the measurement light at grazing incidence onto the test mask.

4. The measuring system according to claim 1 , further comprising:
a test mask having the test structure configured as a test structure cutout and an illumination cutout offset with respect to the test structure cutout, and
a reflective element arranged at an opposing side of the test mask relative to the measurement light radiating device, said reflective element being configured to direct the measurement light through the test structure cutout after said light has passed through the illumination cutout.

5. The measuring system according to claim 4 ,
wherein the reflective element is configured to focus the measurement light.

6. The measuring system according to claim 4 , further comprising:
two further reflective elements arranged at the opposing side of the test mask relative to the measurement light radiating device such that the measurement light, after passing through the illumination cutout, is additionally deflected at the two further reflective elements before passing through the test structure cutout.

7. The measuring system according to claim 4 ,
wherein the reflective element is configured as a diffusing plate.

8. The measuring system according to claim 4 ,
wherein the test mask and the reflective element are provided in a mask module dimensioned as a product reticle configured for exposure in an EUV projection exposure apparatus for lithography.

9. The measuring system according to claim 1 ,
wherein the test structure is configured as a hole structure and the evaluation device is configured to determine, for dimensioning of the hole structure, a value deviating from a real dimensioning of the hole structure utilizing an optimization calculation when determining the imaging quality of the lens.

10. The measuring system according to claim 1 ,
further comprising a correction plate arranged in a beam path of the measurement light downstream of an interaction of the measurement light with the diffractive test structure, which correction plate is configured to have an optical effect on the measurement light, which optical effect varies in a direction transverse to a propagation direction of the measurement light at the correction plate.

11. The measuring system according to claim 10 ,
wherein the correction plate comprises a transmissive layer having a varying thickness.

12. A measuring system for measuring an imaging quality of a lens comprising:
a lens holder configured to hold the lens,
a measurement light radiating device configured to produce measurement light,
a first diffractive test structure arranged on an object side of the lens when arranged in the lens holder such that a test wave is generated by diffraction of the measurement light at the first diffractive test structure,
a second diffractive test structure arranged on an image side of the lens when arranged in the lens holder such that a reference wave is generated by diffraction of the measurement light at the second diffractive test structure, and
a detector configured to record an interference pattern generated by superposition of light from the test wave having interacted with the lens and light from the reference wave.

13. The measuring system according to claim 12 , further comprising:
a reference beam generating structure arranged on the object side of the lens when arranged in the lens holder, the reference beam generating structure being configured to form a reference beam from the measurement light and to direct the reference beam onto the second diffractive test structure.

14. The measuring system according to claim 12 , further comprising:
a diffraction grating arranged in a beam path of the test wave such that the test wave is split into differently oriented beams, wherein a first of the beams is directed onto the second diffractive structure and a second of the beams is directed onto the detector to generate the interference pattern by superposition with the reference wave.

15. The measuring system according to claim 12 ,
wherein the second diffractive test structure is configured as a light absorbing structure in a light reflecting background and the detector is arranged on the object side of the lens when arranged in the lens holder.

16. The measuring system according to claim 12 ,
which is configured such that, with the lens arranged in the lens holder, the interference pattern is generated by superposition of light from the test wave having traversed the lens two times and light from the reference wave having traversed the lens one time after generation of the reference wave at the second diffractive structure.

17. An arrangement comprising:
an extreme ultraviolet (EUV) lens for an inspection apparatus, configured for imaging at least one section of a substrate to be inspected into a detection plane and
a measuring system for measuring an image quality of the lens, said measuring system comprising:
a diffractive test structure,
a measurement light radiating device configured to radiate measurement light in the EUV wavelength range onto the test structure,
a variation device configured to vary at least one image-determining parameter of an imaging of the test structure effected by the lens,
a detector configured to record an image stack comprising a plurality of images generated with mutually differing image-determining parameters varied by the variation device, and
an evaluation device configured to determine the imaging quality of the lens from the image stack.

18. An inspection apparatus for inspecting a surface of a substrate for microlithography comprising:
an extreme ultraviolet (EUV) lens for imaging at least one section of a surface of a substrate to be inspected into a detection plane with imaging radiation, and
a measuring system for measuring an imaging quality of the lens, said measuring system comprising:
a diffractive test structure,
a measurement light radiating device configured to radiate measurement light in the EUV wavelength range onto the test structure,
a variation device configured to vary at least one image-determining parameter of an imaging of the test structure effected by the lens,
a detector configured to record an image stack comprising a plurality of images generated with mutually differing image-determining parameters varied by the variation device, and
an evaluation d

Assignees

• Zeiss Carl Smt Gmbh

Inventors

• Frese Ralf
• Samaniego Michael
• Deguenther Markus
• Haidner Helmut
• Hoch Rainer
• Schriever Martin

Classifications

• G03F7/706

  Aberration measurement · CPC title

• G01M11/0207 Primary

  Details of measuring devices · CPC title

• G01M11/005 Primary

  Testing of reflective surfaces, e.g. mirrors · CPC title