Method of operating a projection exposure tool for microlithography

Patent metadata

Field	Value
Publication number	US-9442381-B2
Application number	US-201313939859-A
Country	US
Kind code	B2
Filing date	Jul 11, 2013
Priority date	Jan 20, 2011
Publication date	Sep 13, 2016
Grant date	Sep 13, 2016

Abstract

A method of operating a projection exposure tool for microlithography is provided. The projection exposure tool has a projection objective for imaging object structures on a mask into an image plane using electromagnetic radiation, during which imaging the electromagnetic radiation causes a change in optical properties of the projection objective. The method comprises the steps of: providing the layout of the object structures on the mask to be imaged and classifying the object structures according to their type of structure, calculating the change in the optical properties of the projection objective effected during the imaging process on the basis of the classification of the object structures, and using the projection exposure tool for imaging the object structures into the image plane, wherein the imaging behavior of the projection exposure tool is adjusted on the basis of the calculated change of the optical properties in order to at least partly compensate for the change of the optical properties of the projection objective caused by the electromagnetic radiation during the imaging process.

First claim

The invention claimed is:

1. A method of operating a microlithography projection exposure tool comprising a projection objective, the projection objective being configured to use electromagnetic radiation to image object structures on a mask into an image plane, the method comprising:
calculating a change in optical properties of the projection objective caused by the electromagnetic radiation during an imaging process, the calculation of the change in optical properties being done on the basis of a Fourier transform of a layout of the mask; and
adjusting the imaging behavior of the projection exposure tool on the basis of the calculated change of the optical properties to at least partly compensate for the change of the optical properties of the projection objective,
wherein calculating the change in the optical properties is performed on the basis of thermal eigenmodes of at least one single optical element of the projection objective.

2. The method of claim 1 , comprising classifying the object structures on the basis of their type of structure.

3. The method of claim 2 , wherein calculating the change of the optical properties of the projection objective comprises calculating an angular distribution of the electromagnetic radiation entering the projection objective for each of the classified types of structure.

4. The method of claim 2 , wherein classifying the object structures comprises determining sizes of respective areas covered by the different types of structures on the mask.

5. The method of claim 1 , comprising:
during the imaging process, illuminating the mask with the electromagnetic radiation in a specific illumination mode;
defining an angular distribution of the electromagnetic radiation illuminating the mask during the imaging process; and
calculating the change in the optical properties on the basis of the illumination mode.

6. The method of claim 1 , wherein performing the Fourier transform comprises classifying the object structures, the classification comprising portioning of the mask into at least first and second regions, wherein the object structures in the first region are more densely arranged than the object structures in the second region.

7. The method of claim 1 , comprising:
calculating a deviation of the wave front in the image plane due to the change in the optical properties; and
adjusting the imaging behavior of the projection exposure tool to compensate for the calculated wave front deviation.

8. The method of claim 1 , comprising adjusting the imaging behavior of the projection objective to correct the change in the optical properties of the projection objective caused by the electromagnetic radiation to reduce at least one lithographic imaging error having an impact on the lithographic image for the layout, wherein the reduction of the lithographic imaging error has a higher priority than a smoothing of the overall wave front deviation of the lithographic image.

9. The method of claim 1 , wherein the Fourier transform of the layer is convolved with an angular distribution of the electromagnetic radiation illuminating the mask during the imaging process.

10. The method of claim 9 , wherein the convolution yields a parameter related to an effective pupil.

11. The method of claim 10 , wherein the parameter is a distribution of diffraction angles of radiation entering the projection objective for each of a plurality of classified types of object structures.

12. The method of claim 1 , wherein the change of the optical properties of the projection objective is caused by heating.

13. The method of claim 12 , wherein effects caused by heating are corrected dynamically.

14. The method of claim 12 , wherein the projection objective comprises a plurality of lenses and the heating is lens heating.

15. The method of claim 14 , wherein the calculation takes into account a distribution of diffraction angle of radiation diffracted from the mask.

16. The method of claim 14 , wherein the calculation of the change in optical properties is based on an angular distribution of electromagnetic radiation at the mask and the Fourier transform of the mask.

17. The method of claim 16 , wherein the imaging behavior of the projection exposure tool is adjusted by manipulating a position of at least one optical element in the projection objective.

18. The method of claim 17 , wherein the manipulation comprises moving a lens along an optical axis of the projection objective.

19. The method of claim 17 , wherein the manipulation comprises turning a lens with respect to an optical axis of the projection objective or deforming the at least one optical element.

20. A method of operating a microlithography projection exposure tool comprising a projection objective, the projection objective being configured to use electromagnetic radiation to image object structures on a mask into an image plane, the method comprising:
determining at least one lithographic imaging error that will have an impact on the lithographic image for a given layout of the object structures on the mask;
imaging the object structures into the image plane; and
adjusting the imaging behavior of the projection objective to correct a change in the optical properties of the projection objective caused by the electromagnetic radiation so that the at least one lithographic imaging error is reduced with a higher priority than a smoothing of the overall wave front deviation of the lithographic image, wherein the smoothing is targeted to segments of a pupil of the projection objective that are traversed by the electromagnetic radiation during the imaging,
wherein calculating the change in the optical properties is performed on the basis of thermal eigenmodes of at least one single optical element of the projection objective.

21. The method of claim 20 , comprising classifying the object structures on the basis of their type of structure.

22. The method of claim 21 , wherein calculating the change of the optical properties of the projection objective comprises calculating an angular distribution of the electromagnetic radiation entering the projection objective for each of the classified types of structure.

23. The method of claim 21 , wherein classifying the object structures comprises determining sizes of respective areas covered by the different types of structures on the mask.

24. The method of claim 21 , wherein classifying the object structures comprises portioning of the mask into at least first and second regions, wherein the object structures in the first region are more densely arranged than the object structures in the second region.

25. The method of claim 20 , comprising:
during the imaging process, illuminating the mask with the electromagnetic radiation in a specific illumination mode;
defining an angular distribution of the electromagnetic radiation illuminating the mask during the imaging process; and
calculating the change in the optical properties on the basis of the illumination mode.

26. The method of claim 20 , comprising:
calculating a deviation of the wave front in the image plane due to the change in the optical properties; and
adjusting the imaging behavior of the projection exposure tool to compensate for the calculated wave front deviation.

27. An apparatus, comprising:
an input device configured to receive a layout of object structures on a mask to be imaged by a proje

Assignees

• Zeiss Carl Smt Gmbh

Inventors

• Conradi Olaf
• Totzeck Michael
• Loering Ulrich
• Juergens Dirk
• Mueller Ralf
• Wald Christian

Classifications

• G03F7/70483 Primary

  Information management; Active and passive control; Testing; Wafer monitoring, e.g. pattern monitoring · CPC title

• G03F7/70141 Primary

  Illumination system adjustment, e.g. adjustments during exposure or alignment during assembly of illumination system · CPC title

• G03F7/708

  Construction of apparatus, e.g. environment aspects, hygiene aspects or materials · CPC title

• G03F7/70891 Primary

  Temperature · CPC title

• G03F7/70516

  Calibration of components of the microlithographic apparatus, e.g. light sources, addressable masks or detectors · CPC title