| Diffractive optics for soft x rays have uses both in microlithography and microscopy. One possible future method for the mass production of microelectronics is projection EUV, (extreme ultraviolet or very soft x-ray), lithography. Diffractive optical elements for an EUV shearing interferometer were designed and fabricated. An alternative method for microlithography using soft x-ray holograms was investigated. A similar technique, spatial frequency multiplication, was investigated as possible technique for the enlarging of Fresnel zone plates. The fringes of a zone plate were successfully produced with this technique, but a large amount of noise was also present.; Much of the work presented here focuses on the fabrication and testing of Fresnel zone plates. Fresnel zone plates are used as the lens in a soft x-ray microscope, and the resolution performance of the x-ray microscope is ultimately determined by the Fresnel zone plate. Fresnel zone plates have a spatial resolution which is approximately equal to the outer zone width of the zone plate. A process for the fabrication of Fresnel zone plates was developed to produce zone plates with outer zone widths as small as 30 or even 20 nm. To avoid the large expense of a specialized electron beam lithography tool, this process uses a general purpose electron beam lithography system at Bell Laboratories. Zone plates were fabricated both in nickel and germanium. The diffraction efficiencies and resolution of the zone plates were tested, and both types of zone plates had good diffraction efficiencies and resolution. The nickel zone plates have a rougher appearance when viewed with a scanning electron microscope but have higher diffraction efficiencies than the germanium zone plates. The ability to detect features of size and spacing smaller than 30 nm was demonstrated in a scanning transmission x-ray microscope using a zone plate with a 30 nm outer zone width. |
