Sapphire hard X-ray Fabry-Perot resonators for synchrotron experiments.

Hard X-ray Fabry-Perot resonators (FPRs) made from sapphire crystals were constructed and characterized. The FPRs consisted of two crystal plates, part of a monolithic crystal structure of Al2O3, acting as a pair of mirrors, for the backward reflection (0 0 0 30) of hard X-rays at 14.3147 keV. The dimensional accuracy during manufacturing and the defect density in the crystal in relation to the resonance efficiency of sapphire FPRs were analyzed from a theoretical standpoint based on X-ray cavity resonance and measurements using scanning electron microscopic and X-ray topographic techniques for crystal defects. Well defined resonance spectra of sapphire FPRs were successfully obtained, and were comparable with the theoretical predictions.

Improving feature size uniformity from interference lithography systems with non-uniform intensity profiles.

The non-uniform intensity profile of Gaussian-like laser beams used in interference lithography (IL) leads to a non-uniform dose and feature size distribution across the sample. Previously described methods to improve dose uniformity are reviewed. However, here we examine the behavior of the non-uniformity from the viewpoint of photoresist response rather than the IL system configuration. Samples with a fixed intra-sample dose profile were exposed with an increasing average dose. A line/space pattern with a period of 240 nm across an area of 2 × 2 cm(2) was produced using IL on identical samples using a HeCd laser operated at 325 nm and a Lloyd's mirror IL system. A binary model of photoresist response predicts that the absolute range of line widths in nanometers should be significantly reduced as the overall sample dose is increased. We have experimentally verified a reduction in the range of line widths within a given sample from 50 to 16 nm as the overall dose is increased by only 60%. This resulted in a drop in the narrowest line width from 120 to 65 nm. An etch process is demonstrated to increase the line width by generating a wider secondary chrome hard mask from the narrowly patterned primary chrome hard mask. The subsequent fabrication of a silicon nanoimprint mold is used as a demonstration of the technique.