Abstract: Ringfield projection apparatus using x-ray radiation e.g. of 1.30 .ANG. wavelength is suitable for lithographic patterning in the fabrication of integrated circuits at design rules of 0.25 .mu.m and below. The design permits reduction from an enlarged mask as well as substantial throughput, the latter due to unexpectedly large slit width. Incorporation of a folding mirror improves fabrication expediency by moving the device being fabricated to the other side of the system from the mask.

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%.