Microelectronic Technologies for Elements of Silicon Refractive X-Ray Optics

The investigation focuses on the development and research of plasma etching processes for the manufacturing of silicon refractive X-ray optical elements: planar compound lenses and also reflective devices - mirror interferometers. Although silicon is not the best material for refractive optics because its refractive and absorption characteristics are concede to materials made from lighter chemical elements, impressive advances in silicon technology in MEMS (micro-electromechanical systems) and nanoelectronics have made it possible to achieve record-breaking precision in the formation of structures, which concerns not only geometry but also minimal roughness. A 100-lens interferometer (with 29 lenses in each channel) was manufactured using the proposed technology. Its' focusing capabilities were investigated both numerically and experimentally, although the fringes with a width of 2.0μm turned out to be wider than the calculated ones $(0.5 \mu\mathrm{m})$; these effects should be attributed to the finite size of the radiation source. The peak-to-peak surface roughness of the lenses was measured to be approximately 20 nm, whereas RMS (root mean square) sidewall roughness measured by SEM, AFM and Optical Profiler does not exceed 2 nm/um. This level of roughness does not significantly affect the formation of interference patterns.