Optical inspection system and method

1. An inspection system comprising:

optics;

an object support for mounting an object in a region of an object plane of the optics;

a bright-field light source;

a dark-field light source;

an image detector having a radiation sensitive substrate disposed in a region of an image plane of the optics; and

a beam dump;

wherein the optics comprise an objective lens, a projection lens, first, second, and third mirrors, and a beam splitter providing an imaging beam path, a bright-field illumination beam path and a dark-field illumination beam path and are arranged:

such that the following components are disposed in the imaging beam path in the following order: the object plane, the objective lens, the first mirror, the beam splitter, and the radiation sensitive substrate;

such that the following components are disposed in the bright field illumination beam path in the following order: the bright-field light source, the beam splitter, the first mirror, the objective lens, and the object plane; and

such that the following components are disposed in the dark field illumination beam path in the following order: the dark field light source, the second mirror, the projection lens, the third mirror, the object plane, and the beam dump;

wherein a first plane defined by an optical axis of the imaging beam path between the objective lens and the first mirror and an optical axis of the imaging beam path between the first mirror and the beam splitter is not co-planar with a second plane defined by an optical axis of the dark-field illumination beam path between the second third mirror and the object plane and an optical axis of the dark-field illumination beam path between the object plane and the beam dump.

2. The inspection system according to claim 1 wherein, when seen projected into a third plane that is parallel to the object plane, the beam splitter is located closer to the projection lens than to the beam dump.

3. The inspection system according to 1 wherein, when seen projected into a third plane that is parallel to the object plane, the dark-field light source is located closer to the beam dump than to the beam splitter.

4. The inspection system according to claim 1 further comprising an object supply apparatus for moving the object towards and away from the object plane and configured to translate, when seen projected into a third plane that is parallel to the object plane, by a distance corresponding to at least a diameter of an object field in a loading direction oriented under an angle relative to a portion of the dark-field illumination beam path which is smaller than an angle between a portion of the imaging beam path and the portion of the dark-field illumination beam path.

5. The inspection system according to claim 1 wherein the projection lens has an extension in a first direction transverse to the dark-field illumination beam path which is more than 1.5 times greater than an extension in a second direction transverse to the dark-field illumination beam path and orthogonal to the first direction.

6. The inspection system according to claim 1 wherein a dark-field illumination beam is deflected at the second mirror by an angle less than 80°.

7. The inspection system according to claim 1 wherein the second mirror has a flat mirror surface.

8. The inspection system according to claim 1 wherein the third mirror has a flat mirror surface.

9. The inspection system according to claim 1 wherein an angle between a direction of incidence of a dark-field illumination beam on the object plane and a surface normal of the object plane is greater than 40°.

10. The inspection system according to claim 1 wherein an angle between the first plane and the second plane is less than 70°.

11. The inspection system according to claim 1 wherein an angle between the first plane and the second plane is less than 60°.

12. The inspection system according to claim 1 wherein the beam dump comprises first and second light absorbing portions, and wherein the second light absorbing portion of the beam dump is arranged to receive a portion of an illumination beam light reflected from the first light absorbing portion.

13. The inspection system according to claim 11 wherein the angle is less than 50°.

14. The inspection according to claim 12 wherein the first light absorbing portion is arranged to receive a portion of an illumination beam reflected from the object on a surface shaped such that pairs of surface normals intersecting the surface at spaced apart locations converge.