Abstract
The results of an investigation on oxidation processes in Mo/Be multilayer nanofilms are presented. The films annealed both in ambient atmosphere and in vacuum. The extreme ultraviolet (EUV) and X-ray reflectivity of the samples at 11.34 and at 0.154 nm respectively were measured before and after the treatment. No noticeable changes in film thicknesses and boundaries were observed during the annealing at temperatures up to 300°C. An oxidation mechanism of the nanofilms Mo/Be is established and the activation energy of the oxidation process is estimated to be 38 kJ/mol. To determine an absolute quantity of oxygen in the oxidized layers, a simple technique based on the EUV reflectivity data is proposed, and the range of its applicability is subsequently analysed.
Highlights
New projects for solar corona imaging impose new requirements for material combinations used in multilayer mirror (MLM) designs such as to provide both high reflectance and a good spectral selectivity in the EUV range
The film thicknesses, the profile of transition layers at the boundaries and film densities in the deposited MLMs were retrieved from a joint analysis of grazing incidence X-ray reflectivity (GIXR) data and a near-normal incidence reflectivity of samples measured at 11.34 nm
The presented study of the oxidation processes and effects of annealing on structural and reflective properties of Mo/Be MLMs revealed a number of conclusions
Summary
New projects for solar corona imaging impose new requirements for material combinations used in multilayer mirror (MLM) designs such as to provide both high reflectance and a good spectral selectivity in the EUV range. Taking into account the multi-mirror nature of modern lithography projection schemes, this can result in a significant economic benefit for mass production of chips For both space and lithography applications, a good temporal stability of the multilayer characteristics is extremely important, as well as a resistance to heating for the coatings operating in an elevated temperature environment or exposed to a high radiation flux. In the paper the questions of samples preparation, characterization and annealing are given in details, followed by the stability evaluations
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