Angular and energy dependence of ion bombardment of Mo/Si multilayers

Abstract

The process of ion bombardment is investigated for the fabrication of Mo/Si multilayer x-ray mirrors using e-beam evaporation. The ion treatment is applied immediately after deposition of each of the Si layers to smoothen the layers by removing an additional thickness of the Si layer. In this study the parameters of Kr ϩ ion bombardment have been optimized within the energy range 300 eV-2 keV and an angular range between 20°and 50°. The optical performance of the Mo/Si multilayers is determined by absolute measurements of the near-normal-incidence reflectivity at 14.4 nm wavelength. The multilayer structures are analyzed further with small-angle reflectivity measurements using both specular reflectivity and diffuse x-ray scattering. The optimal smoothening parameters are obtained by determining the effect of ion bombardment on the interface roughness of the Si layer. The optimal conditions are found to be 2 keV at 50°angle of incidence with respect to the surface. These settings result in 47% reflectivity at 85°( ϭ14.4 nm͒ for a 16-period Mo/Si multilayer mirror, corresponding to an interface roughness of 0.21 nm rms. Analysis shows that the interface roughness is determined by ion induced viscous flow, an effect which increases with ion energy as well as angle of incidence. In order to determine the effect of intermixing of the Si and Mo atoms, the penetration depth of the Kr ϩ ions is calculated as a function of ion energy and angle of incidence. Furthermore, the angular dependence of the etch yield, obtained from the in situ reflectivity measurements, is investigated in order o determine the optimal ion beam parameters for the production of multilayer mirrors on curved substrates. © 1997 American Institute of Physics. ͓S0021-8979͑97͒04716-6͔

Temperature induced diffusion in Mo/Si multilayer mirrors

“…From previous experiments, where ion bombardment has been investigated, it has been concluded that during ion bombardment the smoothening effect is mainly caused by viscous flow. 35 Whether the smoothing effect by temperature optimization is caused by diffusion or viscous flow needs to be investigated in the future.…”

Damage mechanisms of MoN/SiN multilayer optics for next-generation pulsed XUV light sources

“…The MoN/SiN multilayer coatings used in this work have been deposited on superpolished Si substrates using e-beam evaporation of Mo atoms and magnetron sputtering of Si atoms in a UHV background of 1×10 8 mbar, with post-deposition smoothing using low energy ion treatment of the Si layers [15][16][17][18]. Nitridation of the Mo and Si layers was achieved by low energy nitrogen ion treatment during deposition [19][20][21].…”

Effect of thin V insertion layer into Ta film on the performance of Ta diffusion barrier in Cu metallization

“…Concerning ion beam process, energetic ion bombardment increases viscous flow and surface diffusion of adatom, which can significantly reduce interface roughness of Ta/ V/Ta films prepared by IBAD. 10 It has been also reported that multilayer films produced with e-beam deposition in combination with ion bombardment showed a reduced interface roughness. 11,12 The additional sharp interfaces between Ta and V can modify the microstructure of Ta film, in particular, the structure of grain boundaries.…”