US 8,576,376 B2Granted

Imaging optical system and projection exposure system for microlithography

AssigneeCarl Zeiss SMT GmbH

InventorHans-Juergen Mann

Life of this patent

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Abstract

An imaging optical system includes a plurality of mirrors that image an object field in an object plane into an image field in an image plane. At least one of the mirrors is obscured, and thus has a opening for imaging light to pass through. The fourth-last mirror in the light path before the image field is not obscured and provides, with an outer edge of the optically effective reflection surface thereof, a central shadowing in a pupil plane of the imaging optical system. The distance between the fourth-last mirror and the last mirror along the optical axis is at least 10% of the distance between the object field and the image field. An intermediate image, which is closest to the image plane, is arranged between the last mirror and the image plane. The imaging optical system can have a numerical aperture of 0.9. These measures, not all of which must be effected simultaneously, lead to an imaging optical system with improved imaging properties and/or reduced production costs.

Claims26

Dependent claims

An imaging optical system which during operation directs light along a path to image an object field in an object plane to an image field in an image plane, the imaging optical system comprising:

at least six mirrors positioned along an optical axis of the imaging optical system, where the at least six mirrors direct the light along the path,
wherein at least one of the mirrors has an opening through which the light passes, and a distance along the optical axis between a fourth-last mirror in the path and a last mirror in the path is at least 10% of the distance between the object field and the image field along the optical axis,
wherein the distance is between a piercing point of the optical axis and the fourth-last mirror and a piercing point of the optical axis and the last mirror,
wherein the piercing point of the fourth-last mirror is a point where the optical axis passes a reflection surface of the fourth-last mirror or a point where the optical axis passes a surface which carries on continuously from the reflection surface of the fourth-last mirror based on the optical design of the fourth-last mirror, and the piercing point of the last mirror is a point where the optical axis passes a reflection surface of the last mirror or a point where the optical axis passes a surface which carries on continuously from the reflection surface of the last mirror based on the optical design of the last mirror.

1 more element

Dependencies are inferred from the claim text.

Facts

Application: 12/767,521Filed 26 Apr 2010 · continuation
Priority: DE 10 2007 051 67026 Oct 2007
Published: US 2010/0231885 A116 Sep 2010
Granted: 5 Nov 2013
Term ends: Not estimatedThe source records don’t support an estimate.

Classification9 codes

G03F 7/702
Mask illumination systems: reflective illumination, i.e. reflective optical elements other than folding mirrors, e.g. extreme ultraviolet [EUV]…
G02B 17/02
Systems with reflecting surfaces, with or without refracting elements: catoptric systems, e.g. image erecting and reversing system
G02B 17/0652
Using more than three curved mirrors: on-axis systems with at least one of the mirrors having a central aperture
G03F 7/70058
Microphotolithographic exposure; Apparatus therefor: mask illumination systems