CHARACTERIZATION OF ULTRA SMOOTH INTERFACES IN MO SI-MULTILAYERS/

The interface structure of Mo/Si-multilayers prepared by Pulsed Laser Deposition (PLD) on Si substrates at room temperature has been investi gated. Already the in-situ ellipsometer data acquired during film grow th indicate a particular behaviour of this material system that is cau sed by reaction/diffusion processes of the condensing atoms. MoSix int erlayers are formed both at the Mo on Si- and at the Si on Mo-interfac es. The results of multilayer characterization carried out by SNMS and RES show similar concentration profiles for both types of the interla yers. More detailed information about interface structure and morpholo gy can be provided by HREM investigations. In the TEM micrographs of v arious multilayers prepared for different laser light wavelengths an i mprovement of layer stack quality, i.e. formation of abrupt interfaces , with increasing photon energy is observed. Layer stacks having almos t ideally smooth interfaces were synthesized by UV-photon ablation. HR EM micrographs of these multilayers show a pronounced separation of sp acer and absorber layers. The roughness sigma(R) of the interfaces bet ween the amorphous Si- and MoSix-layers was determined by image analys is. On the average a level sigma(R) approximate to 0.1 nm is found. Th ere is no indication for roughness replication or amplification from i nterface to interface as it is known from the appropriate products of conventional thin film technologies.