Carl Zeiss Smt Gmbh

Markus Koch

Renzo Capelli

Dirk Hellweg

Klaus Gwosch

Martin Dietzel

Lars Stoppe

Christoph Husemann

Ulrich Matejka

Thomas Scheruebl

Walter Pauls

Mario Laengle

Michael Kamp-Froese

Manuel Decker

Beat Marco Mout

Dmitry Simakov

Lukas Fischer

Grizelda Kersteen

Tobias Mueller

Daniel Pagel

To determine an imaging quality of an optical system when illuminated by illumination light within an entrance pupil or exit pupil, a test structure is initially arranged in an object plane of the optical system and an illumination angle distribution for illuminating the test structure with the illumination light is specified. The test structure is illuminated at different distance positions relative to the object plane. An intensity of the illumination light is measured in an image plane of the optical system, the illumination light having been guided by the optical system when imaging the test structure at each distance position. An aerial image measured in this way is compared with a simulated aerial image and fit parameters of a function set for describing the simulated aerial image are adapted and a wavefront of the optical system is determined on the basis of the result of a minimized difference.

Method for determining an imaging quality of an optical system when illuminated by illumination light within an entrance pupil to be measured

When measuring a reflectivity of an object for measurement light, initially the object and a reflectivity measurement apparatus are provided. The latter includes a measurement light source, an object holder for holding the object and a spatially resolving detector for capturing measurement light reflected by the object. A measurement light beam impinges on a section of the object within a field of view of the measurement apparatus. The reflected measurement light coming from the impinged-upon section of the object is captured. A surface area of the captured section is at most 50 μm×50 μm. The measurement is performed by the detector. Next, at least one reflectivity parameter of the object is determined on the basis of an intensity of the captured measurement light. The result is a measurement method and a metrology system operating therewith, whereby reflectivities in particular of very finely structured objects, such as lithography masks, can be measured with sufficient precision.

Method for measuring a reflectivity of an object for measurement light and metrology system for carrying out the method

To determine an imaging quality of an optical system when illuminated by illumination light within a pupil to be measured of the optical system and/or to qualify the phase effect of a test structure, a test structure that is periodic in at least one dimension is initially arranged in an object plane of the optical system. An initial illumination angle distribution for illuminating the test structure with an initial pupil region, whose area is less than 10% of a total pupil area, is specified and the test structure is illuminated thereby in different distance positions relative to the object plane. In this way, an initial measured aerial image of the test structure is determined. Specifying the illumination distribution, illuminating and determining the aerial image are then repeated for a further illumination angle distribution and an imaging contribution of the optical system is determined from a comparison of the measured aerial images, the imaging quality parameter to be determined and/or a complex-valued diffraction spectrum of the test structure being determined from said imaging contribution. A metrology system for carrying out the method comprises a holder for the test structure, an illumination optical unit, a specification device for specifying the illumination angle distributions, the optical system to be examined in respect of its imaging quality, and a spatially resolving detection device for determining aerial images. This yields an improved imaging quality determination method.

Method for determining an imaging quality of an optical system when illuminated by illumination light within a pupil to be measured

An optical measuring system is used to reproduce a target wavefront of an imaging optical production system when an object is illuminated with illumination light. The optical measuring system comprises an object holder displaceable by actuator means and at least one optical component displaceable by actuator means. Within the scope of the target wavefront reproduction, a starting actuator position set (X), in which each actuator is assigned a starting actuator position, is initially specified. An expected design wavefront (W) which approximates the target wavefront and which the optical measuring system produces as a set wavefront is determined. A coarse measurement of a starting wavefront (W) which the optical measuring system produces as actual wavefront after actually setting the starting actuator position set (X) is carried out. Then, the object holder is adjusted by actuator means until a coarse target wavefront (W) is obtained for a coarse actuator position set (X) in the case of a minimum wavefront deviation between the actual wavefront and the design wavefront (W). Said coarse target wavefront is then subjected to a fine measurement and the at least one optical component is displaced until a fine target wavefront (W) is obtained for a fine actuator position set (X) in the case of a minimum deviation between the actual wavefront setting-in in that case and the design wavefront (W). This reproduction method allows wavefront deviations of the optical measuring system generated by way of targeted misalignment to provide a good approximation of corresponding deviations of the optical production system.

Method for reproducing a target wavefront of an imaging optical production system, and metrology system for carrying out the method

A method and a device for characterizing a mask for microlithography in a characterization process carried out using an optical system, wherein the optical system includes an illumination optical unit and an imaging optical unit and wherein in the characterization process structures of the mask are illuminated by the illumination optical unit, the mask is imaged onto a detector unit by the imaging optical unit and image data recorded by the detector unit are evaluated in an evaluation unit. A method includes the following steps: determining a temporal variation of at least one variable that is characteristic of the thermal state of the optical system, and modifying the characterization process depending on the temporal variation determined.

Method and device for characterizing a mask for microlithography

In detecting the structure of a lithography mask, a portion of the lithography mask is firstly illuminated with illumination light of an at least partially coherent light source in the at least one preferred illumination direction. A diffraction image of the illuminated portion is then recorded by spatially resolved detection of a diffraction intensity of the illumination light diffracted from the illuminated portion in a detection plane. The steps of 'illuminating' and 'recording the diffraction image' are then carried out for further portions of the lithography mask. Between at least two portions of the lithography mask that are thereby detected, there is in each case an overlap region whose surface extent measures at least 5% or more of the smaller of the two portions of the lithography mask. The repetition takes place until the detected portions of the lithography mask completely cover a region of the lithography mask to be detected. The structure of the lithography mask is calculated from the recorded diffraction images of the illuminated portions. A device for carrying out the structure detection method is also specified, which comprises a light source, a spatially-resolving detector and a mask holder. This results in a method and a device for detecting the structure of a lithography mask, in which the demands placed on an optical unit arranged downstream in the beam path from the illumination light of the lithography mask are reduced.

Method for detecting a structure of a lithography mask and device for carrying out the method

For determining a structure-independent contribution of a lithography mask to a fluctuation of the linewidth, recorded 2D intensity distributions () of an unstructured measurement region of a lithography mask are evaluated in a spatially resolved manner.

Method for determining a structure-independent contribution of a lithography mask to a fluctuation of the linewidth

The invention relates to a method for examining a photolithographic mask for the extreme ultraviolet (EUV) wavelength range in a mask metrology apparatus. In this method, at least one structured region of the mask is selected, a scanner photon number in the extreme ultraviolet (EUV) wavelength range for which the mask in the lithographic production run is provided and a metrology photon number in the extreme ultraviolet (EUV) wavelength range with which the measurement is performed are determined. Next, a photon statistics examination mode is established on the basis of the scanner photon number and the metrology photon number and at least one aerial image of the at least one structured region is produced with the mask metrology apparatus.

Method for examining photolithographic masks and mask metrology apparatus for performing the method

For determining a focus position of a lithography mask (e.g., 5), a focus stack of a measurement region free of structures to be imaged is recorded and the speckle patterns of the recorded images are evaluated.

Method for determining a focus position of a lithography mask and metrology system for carrying out such a method

Determining an imaging aberration contribution of an imaging optical unit for measuring lithography masks involves firstly focus-dependently measuring a 3D aerial image of the imaging optical unit as a sequence of 2D intensity distributions in different measurement planes in the region of and parallel to an image plane of an imaging of an object by use of the imaging optical unit. A spectrum of a speckle pattern of the 3D aerial image is then determined by Fourier transformation of the measured 2D intensity distributions having speckle patterns. For a plurality of spectral components in the frequency domain, a focus dependence of a real part RS(z) and an imaginary part IS(z) of said spectral component is then determined. From the determined values of the focus dependence of the real part RS(z) and the imaginary part IS(z), a contribution made to the speckle pattern spectrum by a mask structure, which contribution is to be eliminated, is then separated from an imaging aberration contribution made to the speckle pattern spectrum by the imaging optical unit. The imaging aberration contribution is then represented. This results in a method for determining the imaging aberration contribution of the imaging optical unit having little additional time expenditure in comparison with the measurement time on the respective lithography mask.

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Neu-Ulm, Germany

Markus Koch