Device fabrication entailing plasma-derived x-ray delineation

Process for fabrication of a device comprising at least one element of least dimension .ltoreq.0.25 .mu.m, such process comprising construction of a plurality of successive levels, each level entailing lithographic delineation, in accordance with which a subject mask pattern is imaged on an image plane, ultimately to result in removal of or addition of material in delineated regions, at least one such level entailing ringfield projection lithographic delineation by use of radiation in the soft x-ray spectrum, and in which such radiation is derived from a laser-produced plasma characterized in that emission from the plasma is collected by a collector lens including at least four paired mirror facets, in which members of each pair are symmetrically disposed about an axis of the source and in which paired members individually produce complementary images of the entirely of an illumination field, whereby paired members together produce an evenly illuminated compensated field and the entire illumination field is of an intensity which is the sum of all facet-produced image fields.