Illumination device for projection system and method for fabricating
AssigneeASML Netherlands B.V.
InventorBruce W. Smith
Life of this patent
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Abstract
A masking aperture for a photomask illumination system provides controlled on-axis and off-axis illumination. The masking aperture has a dithered pattern of pixels. The intensity of the pattern controls the illumination of the photomask. The masking aperture pattern defines one or more zones of illumination. Zones comprise elements that are patterned in accordance with a selected wavelength of incident light to diffract the incident light into an illumination pattern for illuminating a photomask. Each of the elements is constructed with a matrix of pixels. In the preferred embodiment the array of pixels is 8×8. The number of elements is generally greater than 3×3.
Claims34
An illumination system comprising:
- a light source;
- and
- a beam shaping optical system arranged in an optical path from said light source;
- wherein said beam shaping optical system comprises a masking aperture comprising:
- a translucent substrate;
- a half-tone dithered pattern on the substrate, said half-tone dithered pattern comprising an array of pixels, each pixel of a clear or opaque type and of the same size, said clear and opaque pixels for respectively passing and blocking incident light, wherein the number, size, and type of the pixels are chosen in accordance with:
- (a) the wavelength of light used to illuminate the photomask, and
- (b) the size and shape of the features of the photomask.
A lithographic apparatus comprising,
- an illumination system arranged to illuminate a mask;
- and
- a projection optical system arranged to project radiation from said mask onto a substrate,
- wherein said illumination system comprises a beam shaping optical system having a masking aperture comprising:
- a translucent substrate, and
- a half-tone dithered pattern on the substrate,
- wherein said half-tone dithered pattern on said substrate comprises an array of pixels, each pixel being a clear or opaque type and of the same size, said clear and opaque pixels being for passing and blocking respectively incident light, wherein the number, size, and type of the pixels are chosen in accordance with:
- (a) the wavelength of light used to illuminate the photomask, and
- (b) the size and shape of the features of the photomask.
Dependencies are inferred from the claim text.