X-ray or gamma ray systems or devices – Specific application – Lithography
Patent
1990-05-30
1991-11-05
Westin, Edward P.
X-ray or gamma ray systems or devices
Specific application
Lithography
378 35, 359859, G21K 500, G02B 510
Patent
active
050635867
ABSTRACT:
Disclosed is apparatus, exemplarily semiconductor X-ray lithography apparatus, that comprises a novel projection system. In preferred embodiments the projection system is adapted for use with radiation of wavelength below about 30 nm. The system comprises four or more mirrors that form a finite conjugate "optical" system that is telecentric at the short conjugate. The mirrors can be selected such that an essentially flat, diffraction limited image is formed. The image field can be two-dimensional, exemplarily a 10.times.10 mm square, and the resolution over the image field can be higher than 0.25 .mu.m.
Exemplarily, the "optical" system comprises, from long to short conjugate, a convex, a concave, a convex, and a concave mirror, with at least two of the mirrors being aspherics. The radius absolute values of the four mirrors are, in the above order and as a fraction of the system focal length, 2.20, 2.59, 2.51, and 2.13 all to within .+-.5%. Equivalently, the radii of the four mirrors are, in the same order, in the ratio of 1.00, 1.18, 1.14, and 0.97, all to within .+-.5%. The axial separations, in the same order and as a fraction of the system focal length, are 1.45, 1.47, 1.10, and 1.21, the last being the separation between the second concave mirror and the image, all within .+-.10%.
REFERENCES:
patent: 4226501 (1980-10-01), Shafer
"Four-Mirror Unobscured Anastigmatic Telescopes with All-spherical Surfaces", by D. R. Shafer, Applied Optics, vol. 17, No. 7, Apr. 1, 1978, pp. 1072-1074.
"Education-Invited Paper", by D. L. Ederer, and Optical Design I, Contributed Papers, by D. C. Sinclair, 1983 Annual Meeting--Optical Society of America, Oct. 18, 1983, p. 1881.
"Wide-Angle Flat-Image Unobscured Telescope with Four Spherical Mirrors", by D. Shafter, David Shafer Optical Design, Inc., Fairfield, Conn., 6 pages.
"Measurement of Soft X-ray Multilayer Mirror Reflectance at Normal Incidence Using Laser-Produced Plasmas", by J. A. Trail et al., Applied Physics Letters, 52(4), Jan. 25, 1988, pp. 269-271.
"Soft X-ray Reduction Lithography Using Multilayer Mirrors", by H. Kinoshita et al., presented at 33rd International Symposium on EIPB, 1989, 23 pages.
"Soft X-ray Projection Lithography Using an X-ray Reduction Camera", by A. M. Hawryluk et al., Journal Vacuum Science Technology, B6(6), Nov./Dec. 1988, pp. 2162-2164.
"Evaporated Multilayer Dispersion Elements for Soft X-rays", by E. Spiller, IBM T. J. Watson Research Center, Yorktown Heights, N.Y., 1981, 7 pages.
Jewell Tanya E.
Rodgers J. Michael
AT&T Bell Laboratories
Pacher E. E.
Westin Edward P.
Wong Don
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