Effect of substrate heating and ion beam polishing on the interface quality in Mo/Si multilayers - X-ray comparative study

Anopchenko A, Jergel M, Majkova E, et al. Effect of substrate heating and ion beam polishing on the interface quality in Mo/Si multilayers - X-ray comparative study. PHYSICA B-CONDENSED MATTER. 2001;305(1):14-20.Three periodic Mo/Si multilayers were prepared by electron-beam evaporation at different conditions. An in situ polishing of amorphous Si layers with Ar+ ions of 800 eV energy and substrate heating to 170 degreesC were used for the two of them which were designed as multilayer mirrors optimized for 13 nm wavelength at normal incidence (30 periods of nominally 6.9 nm). A third multilayer was deposited at room temperature with reduced Mo layer thicknesses and number of periods to suppress interface roughness buildup. The goal was a comparison of ion beam polishing and substrate heating in terms of the interface quality and evaluation of the merit of more sophisticated depositions. The interfaces were studied by specular X-ray reflectivity and interface diffuse scattering measured at Cu K-alpha1 wavelength. The interface morphology parameters are very close on ion beam polishing and substrate heating indicating a similar relaxation mechanism of the growing surface. The main difference is a larger thickness of the Mo5Si3 interlayers with substrate heating, which has practical implications for peak reflectivities. On the other hand, a slightly worse interface replication here is appealing for the applications where a good imaging contrast is of primary importance. At room temperature deposition, the interface roughness is nearly doubled at 3 times smaller number of multilayer periods. (C) 2001 Elsevier Science B.V. All rights reserved