Carl Zeiss Smt Gmbh

Frank Riepenhausen

Bernd Doerband

Rolf Freimann

Matthias Manger

Stefan Schulte

Albrecht Hof

Bernd Dörband

Armin Bich

Dietmar Neugebauer

Martin Schroeter

Helmut Issler

A method and apparatus for characterizing the surface form of an optical element, in particular a mirror or a lens element of a microlithographic projection exposure apparatus, includes: carrying out a plurality of interferometric measurements, in each of which an interferogram is recorded between a test wave emanating from a portion of the optical element in each case and a reference wave, the position of the optical element relative to the test wave being altered between these measurements, and calculating the figure of the optical element on the basis of these measurements. This calculation is carried out iteratively such that, in a plurality of iteration steps, the figure of the optical element is ascertained in each case by carrying out a forward calculation, each of these iteration steps being based in each case on a reference wave that was adapted based on the preceding iteration step.

Method and device for characterizing the surface shape of an optical element

Measuring a shape of an optical surface () of a test object () includes: providing an interferometric measuring device () generating a measurement wave (); arranging the measuring device () and the test object () consecutively at different measurement positions relative to each other, such that different regions () of the optical surface () are illuminated by the measurement wave (); measuring positional coordinates of the measuring device () at the different measurement positions in relation to the test object (); obtaining surface region measurements by interferometrically measuring the wavefront of the measurement wave () after interaction with the respective region () of the optical surface () using the measuring device () in each of the measurement positions; and determining the actual shape of the optical surface () by computationally combining the surface region measurements based on the measured positional coordinates of the measuring device () at each of the measurement positions.

Method of measuring a shape of an optical surface based on computationally combined surface region measurements and interferometric measuring device

A method of measuring a deviation of an optical test surface from a target shape is provided. The method includes directing an incoming beam of electromagnetic radiation onto the test surface to generate a measuring beam that has interacted with the test surface, causing the ray that has interacted with the test surface to pass through an interferometer on a deviated path, performing an interferometric measurement by superimposing a reference beam with the measuring beam to determine a wave front deviation of the measuring beam from the reference beam, determining a retrace error in the wave front deviation, and correcting the measured wave front deviation by eliminating the retrace error therefrom. The differences in aberrations accumulated by the ray having traveled on the deviated path from fictitious aberrations that would have been accumulated by a ray that had traveled on an undeviated path cause the retrace error.

Method and an apparatus for measuring a deviation of an optical test surface from a target shape

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Oberkochen, Germany

Frank Riepenhausen