AES sputter profiling and angle resolved XPS of in situ grown very thin Tantalum‐oxide films

Abstract

AbstractAngle resolved Auger electron spectroscopy (AES) and x‐ray photo‐electron spectroscopy (XPS) are compared to AES sputter depth profiling of ultra thin (<2 nm) Ta2O5 films to study their relative ability to determine thickness. Films were grown in situ by oxygen exposure after sputter claning the Tantalum‐metal surface. This way films between 2 L and 1800 L (1 L = 10−6 Torr s) were obtained. Results show that for such thin films the 50% oxygen amplitude criterion used to determine thickness cannot be applied anymore, because no steady state is reached in the film. On the other hand, angle resolved AES and XPS measurements show systematically higher values than data obtained by sputtering. However, since the former are critically dependent on the precision of the electron mean free path, λ, reasonable agreement can be obtained if one assumes an intermediate λ value between bulk oxide and metal; this can be justified by the presence of suboxides.