Investigation of the thermal stability of Mg/Co periodic multilayers for EUV applications

We present the results of the characterization of Mg/Co periodic multilayers and their thermal stability for the EUV range. The annealing study is performed up to a temperature of 400\degree C. Images obtained by scanning transmission electron microscopy and electron energy loss spectroscopy clearly show the good quality of the multilayer structure. The measurements of the EUV reflectivity around 25 nm (~49 eV) indicate that the reflectivity decreases when the annealing temperature increases above 300\degreeC. X-ray emission spectroscopy is performed to determine the chemical state of the Mg atoms within the Mg/Co multilayer. Nuclear magnetic resonance used to determine the chemical state of the Co atoms and scanning electron microscopy images of cross sections of the Mg/Co multilayers reveal changes in the morphology of the stack from an annealing temperature of 305\degreee;C. This explains the observed reflectivity loss.Comment: Published in Applied Physics A: Materials Science \& Processing Published at http://www.springerlink.com.chimie.gate.inist.fr/content/6v396j6m56771r61/ 21 page

X-ray scattering study of interface roughness correlation in Mo/Si and Ti/C multilayers for X-UV optics

Jergel M, Holy V, Majkova E, et al. X-ray scattering study of interface roughness correlation in Mo/Si and Ti/C multilayers for X-UV optics. PHYSICA B-CONDENSED MATTER. 1998;253(1-2):28-39.The X-ray reflectivity and interface diffuse scattering at grazing incidence were measured on two couples of multilayers, namely on Mo/Si multilayers (50 periods) prepared by e-beam evaporation and sputtering techniques and on e-beam evaporated Ti/C multilayers (87 periods) prepared with and without Ar+ ion-beam polishing after each layer deposition. The results were evaluated using Fresnel's optical algorithm and a semikinematical modification of the distorted-wave Born approximation to extract and compare the basic interface parameters within each couple. For both Mo/Si multilayers, a frequency-dependent vertical correlation function of the interface roughness corresponding to a model of kinetic roughening was applicable, the vertical correlation length (at a given frequency) being more than an order of magnitude shorter for the sputtered sample. This effect may be explained by high lateral mobility of sputtered adatoms when the Ar plasma pressure is below the thermalization threshold. The main effect of polishing the Ti/C multilayer is a decrease of both the lateral and vertical correlation lengths by about an order of magnitude which may be ascribed to an interfacial reaction at the underlying interface induced by penetrating Ar+ ions. Different lateral and vertical correlations of the interface profiles evidenced within each couple of multilayers affect the distribution of the interface diffuse scattering intensity in the reciprocal space which has some implications for X-UV optics applications. (C) 1998 Elsevier Science B.V. All rights reserved

Thermal stability of W1-xSix/Si multilayers under rapid thermal annealing

Senderak R, Jergel M, Luby S, et al. Thermal stability of W1-xSix/Si multilayers under rapid thermal annealing. JOURNAL OF APPLIED PHYSICS. 1997;81(5):2229-2235.W1-xSix/Si multilayers (MLs) (x less than or equal to 0.66) were deposited onto oxidized Si substrates, heat treated by rapid thermal (RTA) and standard furnace annealing up to 1000 degrees C for 30 s and 25 min, respectively, and analyzed by various x-ray techniques and Rutherford backscattering spectrometry. W1-xSix/Si MLs are more stable the higher the value of x because the driving force for interdiffusion is suppressed by the doping; the temperature for complete interdiffusion increases from 500 to 850 degrees C as x increases from 0 to 0.66. The as-deposited MLs were amorphous. Their thermal stability increases with increasing x. The interface roughness is independent of x but increases with increasing RTA temperature. The reflectivity of W1-xSix/Si MLs is lower than that of W/Si because of lower optical contrast. (C) 1997 American Institute of Physics