Plasma profiling time-of-flight mass spectrometry for fast elemental analysis of semiconductor structures with depth resolution in the nanometer range

Abstract

Plasma profiling time of flight mass spectrometry (PP-TOFMS) has recently gained interest as it enables the elemental profiling of semiconductor structures with high depth resolution in short acquisition times. As recently shown by Tempez et al PP-TOFMS can be used to obtain the composition within structures of modern field effect transistors [1]. There, the results were compared to conventional SIMS measurements. In the present study, we compare PP-TOFMS measurements of an Al-/In-/GaN quantum well multi stack to established micro- and nanoanalysis techniques like cathodoluminescence (CL), scanning transmission electron microscopy (STEM), energy dispersive x-ray spectroscopy (EDX) and x-ray diffraction (XRD). We show that PP-TOFMS is able to resolve the layer structure of the sample even more than 500 nm deep into the sample and allows the determination of a relative elemental composition with an accuracy of about 10 rel%. Therefore, it is an extremely rapid alternative method to obtain semiconductor elemental depth profiles without the expensive and time consuming sample preparation required for TEM. Besides, PP-TOFMS offers better depth resolution and more elemental information than, for example, electrochemical capacitance-voltage (ECV) evaluations, since all elements are detected in parallel and not only electrically (ECV) or optically (CL) active elements are observed.