DIFFUSE-X-RAY-SCATTERING MEASUREMENTS OF ROUGHNESS ON ION-ETCHED MULTILAYER INTERFACES

The effect of ion etching on the interface morphologies of Mo/Si multilayers is investigated via measurements of small-angle diffuse scattering. A comparison is made between two electron-beam-deposited multilayers composed of ten Mo/Si double layers, one with each surface ion etched after deposition. It is observed that ion etching preferentially reduces the short-length-scale interfacial roughness. The non-ion-etched sample exhibits a nearly constant diffusely scattered intensity as a function of in-plane momentum transfer (qx) over the measurable qx range. Thus, roughness contributions from very small length scales are dominant. In contrast, the ion-etched sample produces an exponential decay in the diffuse intensity as a function of qx, which is quantitatively inconsistent with predicted line shapes of existing models describing the effect of ion etching on surface morphology. The data is fit by a model that includes an algebraic decay of the real-space height-height correlations. Possible causes for the discrepancy between data and theory are discussed. © 1995 The American Physical Society.