Illumination optical unit for a metrology system and metrology system comprising such an illumination optical unit

Patent metadata

Field	Value
Publication number	US-10168539-B2
Application number	US-201815895210-A
Country	US
Kind code	B2
Filing date	Feb 13, 2018
Priority date	Jun 28, 2013
Publication date	Jan 1, 2019
Grant date	Jan 1, 2019

Abstract

An illumination optical unit serves for illuminating objects to be examined by a metrology system. The illumination optical unit has an optical pupil shaping assembly for generating a defined distribution of illumination angles of illumination light over an object field in which an object to be examined can be arranged. An optical field shaping assembly for generating a defined intensity distribution of the illumination light over the object field is disposed downstream of the pupil shaping assembly in the beam path of the illumination light. The field shaping assembly has at least one optical field shaping element arranged in the region of a pupil plane of the illumination optical unit. This results in an illumination optical unit which ensures an illumination which can be set in a defined manner with regard to an intensity distribution and an illumination angle distribution over the entire object field.

First claim

What is claimed is:

1. An illumination optical unit for illuminating objects to be examined by a metrology system with illumination light, comprising:
an optical pupil homogenizing assembly for generating a defined intensity distribution of the illumination light over a pupil of the illumination optical unit, wherein the pupil homogenizing assembly comprises at least one micromirror array,
wherein the illumination optical unit further comprises a pupil shaping assembly in the beam path of the illumination light, in which the pupil homogenizing assembly is configured to achieve a correction of a homogenization of the illumination light from the pupil shaping assembly over the pupil of the illumination optical unit by adjustment of the at least one micromirror array.

2. The illumination optical unit according to claim 1 , wherein the micromirror array for pupil shaping comprises a diffraction-reflection grating for the illumination light.

3. The illumination optical unit according to claim 2 , wherein the beam path of the illumination light onto the at least one micromirror array is configured in such a way that the illumination light is incident on micromirrors of the micromirror array with an input divergence which is less than a diffraction angle of a first order of diffraction of the diffraction-reflection grating formed by the micromirror array.

4. The illumination optical unit according to claim 1 , wherein the micromirror array comprises micromirrors which can be adjusted continuously within a tilting angle range.

5. The illumination optical unit according to claim 1 , wherein the micromirror array comprises micromirrors which can be switched discretely between two tilting angles.

6. The illumination optical unit according to claim 1 , wherein the beam path of the illumination light onto the at least one micromirror array is configured in such a way that the illumination light is incident on a micromirror principal plane of the micromirror array with an angle of incidence which is greater than 0°.

7. A method for illuminating objects to be examined by a metrology system, the method comprising:
generating, using an optical pupil homogenizing assembly, a defined intensity distribution of the illumination light over a pupil of the illumination optical unit,
wherein the pupil homogenizing assembly comprises at least one micromirror array,
wherein the illumination optical unit further comprises a pupil shaping assembly in the beam path of the illumination light; and

correcting, using the pupil homogenizing assembly, a homogenization of the illumination light from the pupil shaping assembly over the pupil of the illumination optical unit by adjustment of the at least one micromirror array.

8. The method according to claim 7 , wherein the micromirror array for pupil shaping comprises a diffraction-reflection grating for the illumination light.

9. The method according to claim 8 , comprising projecting the illumination light onto the at least one micromirror array in such a way that the illumination light is incident on micromirrors of the micromirror array with an input divergence which is less than a diffraction angle of a first order of diffraction of the diffraction-reflection grating formed by the micromirror array.

10. The method according to claim 7 , wherein the micromirror array comprises micromirrors which can be adjusted continuously within a tilting angle range.

11. The method according to claim 7 , wherein the micromirror array comprises micromirrors which can be switched discretely between two tilting angles.

12. The method according to claim 7 , comprising projecting the illumination light onto the at least one micromirror array in such a way that the illumination light is incident on a micromirror principal plane of the micromirror array with an angle of incidence which is greater than 0°.

Assignees

• Zeiss Carl Ag
• Zeiss Carl Smt Gmbh

Inventors

• Frank Thomas
• Doering Dirk
• Seitz Holger
• Laengle Mario
• Matejka Ulrich

Classifications

• G02B26/08 Primary

  for controlling the direction of light (in light guides G02B6/35) · CPC title

• G02B21/06

  Means for illuminating specimens · CPC title

• G02B27/0905

  Dividing and/or superposing multiple light beams · CPC title

• G02B27/0961 Primary

  Lens arrays (lens arrays per se G02B3/0006) · CPC title

• G02B26/0808

  by means of one or more diffracting elements · CPC title