Unlock instant, AI-driven research and patent intelligence for your innovation.

Catadioptric objective

Inactive Publication Date: 2011-07-26
CARL ZEISS SMT GMBH
View PDF22 Cites 0 Cited by
  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0007]It is an object of the invention to further reduce the aperture obscuration and the lens diameters in objectives of the kind described above. It is a further object of the invention to provide excellent imaging and color correction for the field sizes typical for microlithography and an increase of the image end aperture compared to the state of the art with the least possible use of material.

Problems solved by technology

This correction means is, however, no longer available in the deep ultraviolet wavelength range.
This leads to significant complexity with respect to construction.
The lenses of the objective near to the field are non-symmetrically illuminated whereby asymmetrical thermal deformations and therefore imaging errors which are difficult to correct occur because of the absorption of the lenses.
In addition, a reduction of the contrast transmission function must not necessarily lead to a reduction of the resolution capacity because of the nonlinear response function of the photoresist.

Method used

the structure of the environmentally friendly knitted fabric provided by the present invention; figure 2 Flow chart of the yarn wrapping machine for environmentally friendly knitted fabrics and storage devices; image 3 Is the parameter map of the yarn covering machine
View more

Image

Smart Image Click on the blue labels to locate them in the text.
Viewing Examples
Smart Image
  • Catadioptric objective
  • Catadioptric objective
  • Catadioptric objective

Examples

Experimental program
Comparison scheme
Effect test

first embodiment

[0072]The catadioptric reduction objective includes a catadioptric first partial objective L1 having surfaces 2 to 48 and a refractive second partial objective L2 having the surfaces 50 to 84. The catadioptric first partial objective L1 images the object plane OB slightly demagnified on the intermediate image plane IMI with a magnification ratio βL1=−0.76. The intermediate image plane IMI is imaged by the refractive second partial objective L2 on the image plane IM significantly demagnified with a magnification ratio of βL2=−0.33. In this way, the total magnification ratio β of the object plane OB in the image plane IM is β=−0.25. The circularly-shaped object field OB has a diameter of 91.2 mm and the corresponding image field IM has a diameter of 22.8 mm. If the catadioptric reduction objective is used in lithography, then object field and image field are rectangularly shaped. For example, a rectangularly-shaped field having the X-Y dimensions 22 mm×6 mm can be placed in the circul...

second embodiment

[0098]The lens and mirror intermediate spaces are flushed with helium in the The gas charge with helium affords the advantage that the pressure and temperature dependency of the refractive index with helium in comparison to nitrogen is less by a factor of 10. Thus, the temperature coefficient of the refractive index dn / dT at λ=157.6 nm, T=0° C. and p=1013 mbar for nitrogen is −1.2·10−6 / K and for helium is −0.14·10−6 / K, the pressure coefficient of the refractive index dn / dp for nitrogen is −0.34·10−6 / mbar and, for helium, is −0.036·10−6 / mbar. In the large volumes between the concave mirrors M1′ and M2′, temperature gradients, which occur during the irradiation, lead to convection. For materials with temperature-dependent refractive indices, convection causes a time-dependent deformation of the wavefronts which cannot be corrected. It is therefore advantageous to fill the space between the mirrors with a gas having minimal temperature dependency of the refractive index.

[0099]The numb...

the structure of the environmentally friendly knitted fabric provided by the present invention; figure 2 Flow chart of the yarn wrapping machine for environmentally friendly knitted fabrics and storage devices; image 3 Is the parameter map of the yarn covering machine
Login to View More

PUM

No PUM Login to View More

Abstract

An aspheric reduction objective has a catadioptric partial objective (L1), an intermediate image (IMI) and a refractive partial objective (L2). The catadioptric partial objective has an assembly centered to the optical axis and this assembly includes two mutually facing concave mirrors (M1, M2). The cutouts in the mirrors (B1, B2) lead to an aperture obscuration which can be held to be very small by utilizing lenses close to the mirrors and having a high negative refractive power and aspheric lens surfaces (27, 33). The position of the entry and exit pupils can be corrected with aspherical lens surfaces (12, 48, 53) in the field lens groups. The number of spherical lenses in the refractive partial objective can be reduced with aspherical lens surfaces (66, 78) arranged symmetrically to the diaphragm plane. Neighboring aspheric lens surfaces (172, 173) form additional correction possibilities.

Description

RELATED APPLICATIONS[0001]This application is a reissue of U.S. Pat. No. 6,631,036 which is a continuation-in-part application of patent application Ser. No. 09 / 263,788, filed Mar. 5, 1999, which, now U.S. Pat. No. 6,169,627, in turn, is a continuation-in-part application of patent application Ser. No. 08 / 936,537, filed Sep. 24, 1997, now abandoned.FIELD OF THE INVENTION[0002]The invention relates to catadioptric objective and the use thereof in a microscope or a microlithographic projection exposure apparatus. The catadioptric objective includes spherical and aspherical lens elements and two concave mirrors which face each other. All components of the catadioptric objective, including also the object field and the image field, are arranged centered to a linear optical axis. This class of catadioptric objectives has a central aperture obscuration.BACKGROUND OF THE INVENTION[0003]At wavelengths in the deep ultraviolet range, that is, wavelengths less than 250 nm, mirrors having a pos...

Claims

the structure of the environmentally friendly knitted fabric provided by the present invention; figure 2 Flow chart of the yarn wrapping machine for environmentally friendly knitted fabrics and storage devices; image 3 Is the parameter map of the yarn covering machine
Login to View More

Application Information

Patent Timeline
no application Login to View More
IPC IPC(8): G02B17/00G02B13/14G02B13/18G02B17/08G03F7/20
CPCG02B13/143G02B13/18G02B17/0808G02B17/0892G03F7/70225G03F7/70241G03F7/70275
Inventor SCHUSTER, KARL HEINZ
Owner CARL ZEISS SMT GMBH