Carl Zeiss Smt Gmbh

Martin Dietzel

Renzo Capelli

Dirk Hellweg

Markus Koch

In order to determine a production aerial image of an object to be measured as a result of an illumination and imaging with illumination and imaging conditions of an optical production system, firstly a measurement aerial image of the object to be measured is captured. This is carried out with illumination and imaging conditions of an optical measurement system, which conditions include a predefined measurement illumination setting. Data of the measurement aerial image are generated during the capturing. An object structure of the object to be measured is reconstructed from the data of the captured measurement aerial image by use of a reconstruction algorithm. Data of the reconstructed object structure are generated during the reconstructing. A production aerial image is simulated from the data of the reconstructed object structure with the illumination and imaging conditions of the optical production system. Said conditions include a production illumination setting, which is different than the measurement illumination setting. This results in a determining method in which the requirements made of an optical measurement system used in the determining method, even under demanding illumination and imaging conditions of the optical production system, are relaxed.

Method for determining a production aerial image of an object to be measured

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

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.

Growing community of inventors

Giengen a. d. Brenz, Germany

Martin Dietzel