Patent Number: 
Section: abstract

For use in charged-particle-beam (CPB) microlithography apparatus, hollow-beam apertures are provided that define a substantially annular aperture having very narrow radial width. In a planar embodiment, triangular portions are provided at a midline of a first plane member. The triangular portions have respective angled edges and tips that narrow to a bridge supporting a circular portion. Semicircular cutouts are provided at the midline of respective forward edges of two second members. The radius of each semicircular cutout is slightly larger than the radius of the central portion. As the second members are urged together, a substantially annular aperture is formed between the semicircular cutouts and the central portion. The annular aperture can have extremely narrow width. In other embodiments, a block of beam-absorbing material defines a cylindrical portion having a diameter equal to the diameter of an axial beam-absorbing body, and defines a cylindrical opening, having a diameter equal to the intended outer diameter of the annular opening, beneath the cylindrical portion. Rotation-symmetric portions that are thin in a beam-transmission direction are removed selectively to form a hollow-beam aperture defining an opening that, in a plan view, is substantially annular except for portions missing from the ring.