Illumination optic for projection lithography

Patent metadata

Field	Value
Publication number	US-10928733-B2
Application number	US-202016934652-A
Country	US
Kind code	B2
Filing date	Jul 21, 2020
Priority date	Jan 31, 2018
Publication date	Feb 23, 2021
Grant date	Feb 23, 2021

Abstract

An illumination optical unit for projection lithography illuminates an object field with illumination light along an illumination beam path. The arrangement of field facets of a field facet mirror and also of pupil facets of a pupil facet mirror is such that an illumination channel is guided over each of them. The field facet mirror images a light source image along in each case one illumination channel onto one of the pupil facets. The pupil facet mirror superimposedly images of the field facets into the object field. The illumination optical unit is designed for the settable specification of a spatial resolution of an illumination light illumination of an entrance pupil of a projection optical unit arranged downstream of the object field in the illumination light beam path. The result of this is an illumination optical unit with which illumination light can be used efficiently for high-contrast imaging of the structures to be projected.

First claim

What is claimed is:

1. An illumination optical unit configured to illuminate structures of an object in an object field with illumination light from a light source along an illumination beam path, the illumination optical unit comprising:
a field facet mirror comprising a plurality of field facets; and
a pupil facet mirror comprising a plurality of pupil facets,
wherein:
the field facets and the pupil facets are configured so that in each case a partial beam of the illumination light is guided over exactly one field facet and exactly one pupil facet along an illumination channel from the light source to the object field;
the field facet mirror is a component of a field facet transfer optical unit configured to image a light source image along in each case one illumination channel onto one of the pupil facets;
the pupil facet mirror is a component of a pupil facet transfer optical unit configured to superimposedly image the field facets into the object field; and
the illumination optical unit is configured to set, based on the structures of the object in the object field, a spatial resolution of an illumination light illumination of an entrance pupil of a projection optical unit arranged downstream of the object field in the illumination light beam path to image the structures of the object in the object field into an image field.

2. The illumination optical unit of claim 1 , wherein the field facet mirror is displaceable relative to the light source image to set a distance between the field facets and the light source image.

3. The illumination optical unit of claim 1 , wherein the field facets of the field facet mirror have a settable an optical power.

4. The illumination optical unit of claim 2 , wherein the illumination optical unit is configured so that a displacement of the field facet mirror relative to the light source image to set the distance between the field facets and the light source image does not lead to a change in the light path along the illumination channels between the light source image and the object field.

5. The illumination optical unit of claim 1 , wherein:
the field facet mirror is tiltable over-all;
the pupil facet mirror is tiltable over-all;
the pupil facet mirror is displaceable relative to the light source image to set the distance between the field facets and the pupil facets; and
at least one additional mirror is present in the illumination light beam path of the illumination optical unit between the light source image and the object field.

6. The illumination optical unit of claim 1 , further comprising an entrance pupil transfer optical unit downstream of the pupil facet mirror in the illumination light beam path,
wherein:
the entrance pupil transfer optical unit is configured to image the pupil facets into an entrance pupil of a downstream projection optical unit configured to image the object field into an image field; and
the entrance pupil transfer optical unit is configured to set an imaging scale of the imaging of the pupil facets onto the entrance pupil with a position of the pupil facet mirror relative to the object field staying the same.

7. The illumination optical unit of claim 6 , wherein the entrance pupil transfer optical unit comprises a mirror that is displaceable relative to the pupil facet mirror to set the imaging scale of the imaging of the pupil facets onto the entrance pupil.

8. The illumination optical unit of claim 7 , wherein a mirror of the entrance pupil transfer optical unit has a settable optical power.

9. The illumination optical unit of claim 6 , wherein a mirror of the entrance pupil transfer optical unit has a settable optical power.

10. The illumination optical unit of claim 1 , wherein the pupil facet mirror is configured to set a pupil facet distance of adjacent pupil facets perpendicular to a normal on a reflection surface of the pupil facets.

11. The illumination optical unit of claim 10 , wherein the pupil facets along the pupil facet distance are displaceable relative to one another on a pupil facet carrier of the pupil facet mirror.

12. The illumination optical unit of claim 1 , wherein:
the field facet mirror is displaceable relative to the light source image to set a distance between the field facets and the light source image; and
the field facets of the field facet mirror have a settable an optical power.

13. The illumination optical unit of claim 12 , wherein the illumination optical unit is configured so that a displacement of the field facet mirror relative to the light source image to set the distance between the field facets and the light source image does not lead to a change in the light path along the illumination channels between the light source image and the object field.

14. The illumination optical unit of claim 1 , wherein:
the field facets of the field facet mirror have a settable an optical power;
the field facet mirror is tiltable over-all;
the pupil facet mirror is tiltable over-all;
the pupil facet mirror is displaceable relative to the light source image to set the distance between the field facets and the pupil facets; and
at least one additional mirror is present in the illumination light beam path of the illumination optical unit between the light source image and the object field.

15. The illumination optical unit of claim 1 , further comprising an entrance pupil transfer optical unit downstream of the pupil facet mirror in the illumination light beam path,
wherein:
the entrance pupil transfer optical unit is configured to image the pupil facets into an entrance pupil of a downstream projection optical unit configured to image the object field into an image field;
the entrance pupil transfer optical unit is configured to set an imaging scale of the imaging of the pupil facets onto the entrance pupil with a position of the pupil facet mirror relative to the object field staying the same; and
field facets of the field facet mirror have a settable an optical power.

16. An illumination system, comprising:
an illumination optical unit according to claim 1 ; and
a light source configured to produce the illumination light.

17. An optical system, comprising:
an illumination optical unit according to claim 1 ; and
a projection optical unit configured to image the object field into an image field.

18. An apparatus comprising:
an illumination optical unit according to claim 1 ;
a projection optical unit configured to image the object field into an image field; and
a light source configured to produce the illumination light,
wherein the apparatus is a projection exposure apparatus.

19. The apparatus of claim 18 , further comprising:
an object holder comprising an object displacement drive to displace the object along an object displacement direction; and
a wafer holder comprising a wafer displacement drive to displace a wafer in a manner synchronized with the object displacement drive.

20. A method of using a projection exposure apparatus comprising an illumination optical unit and a projection optical unit, the method comprising:
determining structures of a lithography mask in an object field of the projection optical unit;
based on the determined structures of the lithography mask, setting a spatial resolution of an illumination light illumination of an entrance pupil of the of the projection optical unit, the entrance pupil of the of the projection unit being downstream of the object field;
using the illumination optical unit to illuminate the structures of the li

Assignees

• Zeiss Carl Smt Gmbh

Inventors

• Patra Michael

Classifications

• G03F7/70033

  by plasma extreme ultraviolet [EUV] sources · CPC title

• G03F7/70075 Primary

  Homogenization of illumination intensity in the mask plane by using an integrator, e.g. fly's eye lens, facet mirror or glass rod, by using a diffusing optical element or by beam deflection · CPC title

• G02B19/0095

  for use with ultraviolet radiation · CPC title

• G03F7/702

  Reflective illumination, i.e. reflective optical elements other than folding mirrors, e.g. extreme ultraviolet [EUV] illumination systems · CPC title

• G02B19/0023 Primary

  at least one surface having optical power · CPC title