Optimal low‐energy SIMS conditions for characterizing ZrO2/Si interfaces

Abstract

AbstractDevelopment of high‐K gate dielectric materials has placed a stringent demand for inspection tools with ultrahigh depth resolving power and detection sensitivity. Low‐energy SIMS is potentially the technique of choice provided that the analytical related artifacts are well understood and efficiently suppressed. In this work we profiled superficial and buried metal–organic chemical vapour deposited ZrO2 films and investigated the artifacts involved in SIMS profiling at various beam conditions. It was demonstrated that O2+ beams at near‐normal incidence yielded extremely broad Zr down‐slopes in Si, an artifact likely due to a pronounced preferential sputtering of Si when the instantaneous surface reached the ZrO2/Si interfaces. Suppression of this artifact can be realized by probing O2+ beams at oblique incidence, favorably at 60° for a 1 keV O2+. Nevertheless, the normal‐incidence O2+ beam remained optimal for characterizing the up‐slope of Zr at the polycrystalline Si (polySi)/ZrO2 interface, owing to the minimized matrix effects and suppressed surface roughness. For profiling a gate stack (polySi/ZrO2/Si) at oblique incidences, the high depth resolution of low‐energy SIMS was hindered by the pronounced roughness in poly‐Si. This can be remedied by ion beam smoothing of the poly‐Si prior to SIMS profiling. Using the optimal SIMS conditions, we profiled poly‐Si/ZrO2/Si wafers with and without dopant activation anneal. The SIMS data revealed significant reactions between ZrO2 and Si upon thermal anneal at 1025°C for 10 s. Copyright © 2002 John Wiley & Sons, Ltd.