Shearing interferometer with dynamic pupil fill

a technology of interferometer and pupil fill, which is applied in the field of photolithographic systems, can solve the problems of shorter wavelength light becoming absorbed by glass lenses and light not reaching silicon wafers

Inactive Publication Date: 2005-11-24
ASML HLDG NV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0009] The present invention is directed to a scanning interferometer with dynamic pupil fill that substantially obviates one or more of the problems and disadvantages of the related art.

Problems solved by technology

As chip manufacturers have been able to use shorter wavelengths of light, they have encountered a problem of the shorter wavelength light becoming absorbed by the glass lenses that are intended to focus the light.
Due to the absorption of the shorter wavelength light, the light fails to reach the silicon wafer.

Method used

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  • Shearing interferometer with dynamic pupil fill
  • Shearing interferometer with dynamic pupil fill
  • Shearing interferometer with dynamic pupil fill

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Embodiment Construction

[0024] Reference will now be made in detail to the embodiments of the present invention, examples of which are illustrated in the accompanying drawings.

[0025] It is convenient to characterize field-dependent aberrations of a projections optics (PO) by an aberration of a wavefront of a spherical wave emitted from a corresponding field point in the object plane. Various interferometry techniques can be used to measure aberration of this spherical wave. Shearing interferometry based on an extended incoherent source in the object plane superimposed with an object-plane grating matching the shearing grating is described in J. Braat and A. J. E. M. Janssen, Improved Ronchi test with Extended Source, J. Opt. Soc. Am. A, Vol. 16, No. 1, pp. 131-140, January 1999, incorporated by reference herein. Also, the paper by Naulleau et al., Static Microfield Printing at the ALS with the ETS-2 Set Optic, Proc. SPIE 4688, 64-71 (2002) (http: / / goldberg.lbl.gov / papers / Naulleau_SPIE—4688(2002).pdf), inc...

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Abstract

A wavefront measurement system includes a source of electromagnetic radiation. An illumination system delivers the electromagnetic radiation to an object plane. A source of a diffraction pattern is in the object plane. A projection optical system projects the diffraction pattern onto an image plane, which includes a mechanism (e.g., a shearing grating) to introduce the lateral shear. A detector is located optically conjugate with the pupil of the projection optical system, and receives an instant fringe pattern, resulting from the interference between sheared wavefronts, from the image plane. The diffraction pattern is dynamically scanned across a pupil of the projection optical system, and the resulting time-integrated interferogram obtained from the detector is used to measure the wavefront aberration across the entire pupil.

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention is generally related to photolithography systems, and more particularly, to measuring wavefront parameters in a photolithographic system. [0003] 2. Related Art [0004] Lithography is a process used to create features on the surface of substrates. Such substrates can include those used in the manufacture of flat panel displays, circuit boards, various integrated circuits, and the like. A frequently used substrate for such applications is a semiconductor wafer. One skilled in the relevant art would recognize that the description herein would also apply to other types of substrates. [0005] During lithography, a wafer, which is disposed on a wafer stage (WS), is exposed to an image projected onto the surface of the wafer by an exposure system located within a lithography system. The exposure system includes a reticle (also called a mask) for projecting the image onto the wafer. [0006] The reticle is...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): G01B9/02G01J9/02G01M11/02G03F7/20H01L21/027
CPCG03F7/706G01J9/0215G03F7/70591
Inventor LATYPOV, AZAT M.POULTNEY, SHERMAN K.VLADIMIRSKY, YULI
Owner ASML HLDG NV
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