Device and method for measuring substrates for semiconductor lithography
The invention relates to a device for measuring a substrate for semiconductor lithography, comprising an illumination optical unit, an imaging optical unit and a recording device arranged in the image plane of the imaging optical unit, a diffractive element being arranged in the pupil of the imaging optical unit. The invention also relates to a method for measuring a substrate for semiconductor lithography with a measuring device, the measuring device comprising an imaging optical unit with a pupil, with the following method steps: arranging a diffractive element in the pupil of the imaging optical unit for producing a multifocal imaging, capturing the imaging of a partial region of the substrate, and evaluating the imaging.
1 . A device for measuring a substrate for semiconductor lithography, comprising an illumination optical unit for illuminating a region of the substrate, an imaging optical unit for imaging the substrate onto an image plane, and a recording device arranged in the image plane of the imaging optical unit,
wherein a diffractive element is arranged in a pupil of the imaging optical unit and configured to produce multiple images of the illuminated region of the substrate on the recording device with different amounts of defocusing.
2 . The device of claim 1 ,
wherein the illumination optical unit comprises a stop arranged in a field plane.
3 . The device of claim 1 ,
wherein the diffractive element is formed as a grating.
4 . The device of claim 1 ,
wherein the diffractive element is formed as an amplitude grating, a phase grating, or a combination of an amplitude grating and a phase grating.
5 . The device of claim 1 ,
wherein the recording device is a camera.
6 . The device of claim 3 ,
wherein the grating comprises a locally varying period in one direction.
7 . The device of claim 3 ,
wherein the grating comprises a locally varying period in two directions perpendicular to one another.
8 . The device of claim 3 ,
wherein the grating comprises a distortion corresponding to a non-paraxial wavefront of the defocus.
9 . The device of claim 1 ,
wherein the different amounts of defocusing provided by the diffractive optical element correspond to imaging with different distances between the substrate and the imaging optical unit.
10 . The device of Claim 1 ,
wherein the diffractive element is formed such that radiation energy is allocated equally to the individual multiple images with deviations of less than 2%.
11 . The device of claim 1 ,
wherein the diffractive element is formed such that it can bring about aberrations of a higher order in the imaging.
12 . The device of claim 11 ,
wherein the diffractive element is formed such that the aberrations of a higher order that are brought about by the diffractive element correct aberrations of a higher order of the imaging optical unit.
13 . The device of claim 1 ,
wherein the diffractive element is formed such that it is adjustable.
14 . The device of claim 1 ,
wherein the diffractive element can be pivoted into the pupil of the imaging optical unit.
15 . The device of claim 1 ,
wherein the diffractive element is formed such that it is exchangeable.
16 . The device of claim 1 ,
wherein the device comprises a magazine with a number of differently formed diffractive elements.