Quantitative reconstruction of Ta/Si multilayer depth profiles obtained by Time-of-Flight-Secondary-Ion-Mass-Spectrometry (ToF-SIMS) using Cs+ ion sputtering

摘要

Measured sputter depth profiles of Ta/Si multilayers consisting of 10 alternating layers of Si (10.5 nm thickness) and Ta (7.5 nm thickness) obtained by sputtering with Cs+ ions of 1 keV energy, impinging under an angle of 45 degrees, were re-evaluated by application of the Mixing-Roughness-Information depth (MRI) model for profile reconstruction. To be able to perform the latter, a decrease of the sputtering rate with sputtered depth, a strong and sputtering time dependent matrix effect of the detected Si+ ion intensity as well as preferential sputtering of Si have to be taken into account. The results disclose a similar depth resolution for the Si and Ta layers composed of atomic mixing and roughness contributions. The depth resolution increases with the sputtered depth from 4.2 to 6.8 nm at 50 and 300 s sputtering time, respectively. Except for the first and the last two layers (Nos. 19 and 20), by application of the MRI model a full reconstruction of the measured profiles of the Si and Ta multilayer structure was obtained with a mean error of about +/- 5%. (C) 2015 Elsevier B.V. All rights reserved.