Method of operating a microlithographic projection apparatus

Patent metadata

Field	Value
Publication number	US-2016161845-A1
Application number	US-201615041149-A
Country	US
Kind code	A1
Filing date	Feb 11, 2016
Priority date	Sep 14, 2013
Publication date	Jun 9, 2016
Grant date	—

Abstract

A method of operating a microlithographic projection exposure apparatus includes, in a first step, providing a projection objective that includes a plurality of real manipulators. In a second step, a virtual manipulator is defined that is configured to produce preliminary control signals for at least two of the real manipulators. In a third step, performed during operation of the apparatus, a real image error of the projection objective is determined. In a fourth step, a desired corrective effect is determined. In a fifth step, first virtual control signals for the virtual manipulator are determined. In a sixth step, second virtual control signals for the real manipulators are determined.

First claim

What is claimed is:

1 . A method of operating a microlithographic projection apparatus comprising a projection objective, the projection objective comprising a plurality of optical elements arranged along a light path, the projection objective also comprising a plurality of real manipulators, the method comprising:
defining a virtual manipulator configured to produce, in response to a first virtual control signal applied to the virtual manipulator, preliminary control signals for at least two of the real manipulators according to a predetermined control scheme; during operation of the apparatus, determining:
a real image error of the projection objective;
a desired corrective effect that depends on the real image error; and
depending on the desired corrective effect, the first virtual control signal for the virtual manipulator and second virtual control signals for each of the real manipulators;
determining final control signals for the real manipulators, the final control signals being a function of the first and second virtual control signals; and applying the determined final control signals to the real manipulators so that optical properties of the at least one optical element alter in a manner that results in a modification of the real image error.

2 . The method of claim 1 , further comprising:
illuminating at least a portion of a mask with projection light, the mask arranged in an object plane of the projection objective; and forming an image of the mask in an image plane of the projection objective.

3 . The method of claim 2 , wherein the modification of the real image error is an at least partial correction of the real image error.

4 . The method of claim 3 , wherein, for each real manipulator, the real manipulator is configured to alter, in response to a final control signal applied to the real manipulator, an optical property of at least one of the optical elements.

5 . The method of claim 1 , wherein the modification of the real image error is an at least partial correction of the real image error.

6 . The method of claim 5 , wherein, for each real manipulator, the real manipulator is configured to alter, in response to a final control signal applied to the real manipulator, an optical property of at least one of the optical elements.

7 . The method of claim 1 , wherein, for each real manipulator, the real manipulator is configured to alter, in response to a final control signal applied to the real manipulator, an optical property of at least one of the optical elements.

8 . The method of claim 1 , wherein defining a virtual manipulator comprises determining:
a hypothetical image error of the projection objective; control ranges of each of the real manipulators, the control range of a particular real manipulator defining the allowed values of the final control signals that can be applied to the particular real manipulator; the control scheme so that:
when only hypothetical preliminary control signals produced by the virtual manipulator in response to a hypothetical first virtual control signal are applied to the real manipulators, the real manipulators alter the optical property of the at least one of the optical elements in a manner that results in a modification of the hypothetical image error; and
the hypothetical preliminary control signals are within the determined control ranges.

9 . The method of claim 8 , wherein the modification of the hypothetical image error comprises at least partial correction of the hypothetical image error.

10 . The method of claim 8 , wherein, when only the hypothetical preliminary control signals produced by the virtual manipulator in response to a hypothetical first virtual control signal are applied to the real manipulators, the real manipulators alter the optical property of the at least one of the optical elements in a manner that results in a best possible correction of the hypothetical image error according to a predefined criterion that is used to evaluate the image errors.

11 . The method of claim 10 , wherein:
a residual wavefront deformation, which remains after the correction of the hypothetical image error, is expanded into Zernike polynomials; and a correction of the hypothetical image error is considered as the best possible correction when a maximum absolute value among all Zernike coefficients of this expansion is smaller than a corresponding maximum absolute value among all Zernike coefficients that are obtained if a residual wavefront error is expanded that remains after the correction of the hypothetical image error that is not corrected by the best possible correction.

12 . The method of claim 8 , wherein determining the control scheme comprises solving a minimization problem using a convex programming algorithm.

13 . The method of claim 8 , wherein the control scheme comprises a functional dependency between the hypothetical preliminary virtual control signals and the hypothetical first virtual control signal.

14 . The method of claim 8 , wherein the control range associated with one of the real manipulators depends on the first and/or second virtual control signals that are supplied to another one of the real manipulators.

15 . The method of claim 1 , comprising the determining, for each real manipulator, how an optical wavefront passing through the projection objective is affected when a final control signal is applied to the respective real manipulator.

16 . The method of claim 1 , wherein determining the first virtual control signal for the virtual manipulator and the second virtual control signals for each of the real manipulators comprises solving a minimization problem.

17 . The method of claim 16 , wherein solving the minimization problem comprises using a regularization algorithm and/or singular value decomposition with thresholding.

18 . The method of claim 16 , wherein solving the minimization problem comprises using the Tikhonov regularization algorithm.

19 . The method of claim 1 , wherein at least two real manipulators, for which the virtual manipulator produces preliminary control signals, are configured to alter an optical property of at least two different optical elements.

20 . The method of claim 19 , wherein the at least two different optical elements are separated from each other by at least one further optical element having a curved surface on which projection light impinges during operation of the apparatus.

21 . One or more machine-readable hardware storage devices comprising instructions that are executable by one or more processing devices to perform operations comprising:
defining a virtual manipulator configured to produce, in response to a first virtual control signal applied to the virtual manipulator, preliminary control signals for at least two of real manipulators of a projection objective of a microlithographic projection apparatus according to a predetermined control scheme; during operation of the apparatus, determining:
a real image error of the projection objective;
a desired corrective effect that depends on the real image error; and
depending on the desired corrective effect, the first virtual control signal for the virtual manipulator and second virtual control signals for each of the real manipulators;
determining final control signals for the real manipulators, the final control signals being a function of the first and second virtual control signals; and applying the determined final control signals to the real manipulato

Assignees

• Zeiss Carl Smt Gmbh

Inventors

• Bittner Boris
• Wabra Norbert
• Schoemer Ricarda

Classifications

• G03F7/705

  Modelling or simulating from physical phenomena up to complete wafer processes or whole workflow in wafer productions · CPC title

• G03F1/70 Primary

  Adapting basic layout or design of masks to lithographic process requirements, e.g., second iteration correction of mask patterns for imaging · CPC title

• G06F2119/18

  Manufacturability analysis or optimisation for manufacturability · CPC title

• G06F30/39

  Circuit design at the physical level (physical level design for reconfigurable circuits G06F30/347) · CPC title

• G03F7/70258 Primary

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