Biomedical subjects

Daniel G Stearns

Publications and source records attributed to Daniel G Stearns.

3 recordsLinked to original sources

PubMed2005

High-temperature stability multilayers for extreme-ultraviolet condenser optics.

We investigate the thermal stability of Mo/SiC multilayer coatings at elevated temperatures. Transmission electron microscopy and x-ray diffraction studies show that, upon annealing, a thermally induced structural relaxation occurs that transforms the polycrystalline Mo and amorphous SiC layers in as-deposited multilayers into an amorphous Mo-Si-C alloy and crystalline SiC, respectively. After this relaxation process is complete, the multilayer is stable at temperatures up to 400 degrees C.

Journal Article↗

PubMed2003

High-performance Mo-Si multilayer coatings for extreme-ultraviolet lithography by ion-beam deposition.

An ion-beam deposition system has been used to fabricate Mo-Si multilayer coatings for masks and imaging optics to be used for extreme-ultraviolet lithography. In addition to high reflectivity and excellent profile control, ion-beam deposition has the capability to smooth rough substrates. For example, we achieved reflectivity of 66.8% on a substrate with 0.39-nm roughness. Smoothing can be further enhanced with a second ion source directed at the multilayer coating. The smoothing capabilities relax the requirement on the finish of the mirror and the mask substrates and could dramatically reduce the cost of these components. Thickness profile control is in the +/-0.01% range, and the figure error added to the mirror substrate by errors in the multilayer thickness is less than 0.1 nm. Peak reflectivities obtained on smooth substrates are 67.5-68.6%.

Journal Article↗

PubMed2003

Correction of figure errors on optical surfaces by laser-induced contraction of Mo/Si multilayers.

We demonstrate that laser annealing of Mo/Si multilayers can be used to make controlled modifications of the surface figure of an optical substrate on a nanometer scale. In this experiment a superpolished optical flat was exposed to single pulses from an excimer laser to produce surface depressions of widths that varied from 10 microm to 0.5 mm and of depths in the range 2-50 nm. Simulations of thermally induced contraction of the Mo/Si multilayers are in good agreement with the observed deformations and indicate that the technique can be extended to larger deformations and higher resolution.

Journal Article↗