Optical: systems and elements – Single channel simultaneously to or from plural channels – By partial reflection at beam splitting or combining surface
Reexamination Certificate
2002-09-04
2004-11-30
Mai, Huy (Department: 2873)
Optical: systems and elements
Single channel simultaneously to or from plural channels
By partial reflection at beam splitting or combining surface
C359S571000, C359S350000
Reexamination Certificate
active
06825988
ABSTRACT:
BACKGROUND
The progressive reduction in feature size in integrated circuits (ICs) is driven in part by advances in lithography. ICs may be created by alternately etching material away from a chip and depositing material on the chip. Each layer of materials etched from the chip may be defined by a lithographic process in which light shines through a mask, exposing a photosensitive material, e.g., a photoresist.
The ability to focus the light used in lithography, and hence to produce increasingly smaller line widths in ICs, may depend on the wavelength of light used. Current techniques may use light having a wavelength of about 193 nm. The use of “soft” x-rays (wavelength range of &lgr;≈10 to 20 nm) in lithography is being explored to achieve smaller desired feature sizes. Soft x-ray radiation may also be referred to as extreme ultraviolet (EUV) radiation.
A challenge in EUV lithography is to eliminate all but a narrow desired range of wavelengths from the light used to expose the wafer (typically 13.4 nm with a 2% bandwidth). The multilayer coatings of the mirrors naturally perform this task in the neighborhood of the exposure wavelength, as their reflectivity rapidly falls to nearly zero away from this wavelength. However, much longer wavelengths may still be reflected by the multilayers. In particular, infra-red (IR) and deep ultraviolet (DUV) wavelengths may still reflect off the mirrors. Such wavelengths are eliminated by use of a Spectral Purity Filter (SPF). These can be made of, for example, a thin-film which transmits EUV and absorbs unwanted wavelengths. Another approach is to use a diffraction grating to spread out the wavelengths, and then spatially block non-EUV wavelengths. Critical performance criteria for SPFs are efficiency (% EUV transmitted) and the ability to cool the SPF (absorbed radiation will heat the element). For example, film-type (transmissive) spectral purity filters may absorb 50% or more of incident EUV radiation.
REFERENCES:
patent: 6262845 (2001-07-01), Sweatt
patent: 6289145 (2001-09-01), Solgaard et al.
patent: 2001/0003035 (2001-06-01), Ozarski et al.
patent: 2002/0097385 (2002-07-01), Van Elp et al.
patent: 2002/0127497 (2002-09-01), Brown et al.
Franke, et al. “Super-smooth x-ray reflection grating fabrication”, Journal of Vacuum Sciences & Technology B, (Microelectronics and Nanometer Structure/Processing, Measurement, and Phenomena), vol. 15, No. 6, pp. 2940-2945, Nov./Dec. 1997.
Bristol, et al., “Silicon Diffraction Gratings for Use in the Far-and Extreme-Ultraviolet”, SPIE, vol. 3114, pp. 580-585, 1997.
Fish & Richardson P.C.
Intel Corporation
Mai Huy
LandOfFree
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