Fabrication alignment and test of an all-reflective soft x-ray microlithography objective

摘要

Abstract: A 20 power (20X) all-reflective microlithography objective has been fabricated for use in the soft x-ray region at a wavelength of 13 nm. The design uses the Schwarzschild configuration where two spherical mirrors form a point image from a point object. The centers of curvature of the two mirrors in such a system are coincident. However, to increase field of view, fifth- order spherical must be balanced by third-order spherical. This is accomplished by separating the two curvature centers longitudinally. Lateral separations quickly introduce coma into the wavefront. Holding the curvature center positions rigidly in place relative to the object and image positions is required for maintaining the wavefront quality. Suitable x-ray sources are not common; therefore, the rigidity must also be viewed as a level of ruggedness suitable for transportation from the assembly facility to the test facility. In this paper we share the techniques that we have used to satisfy the requirements of MTF, wavefront quality, ease of alignment, and ruggedness. !0