Orbitrap™-SIMS for accurate quantification of arsenic in SiGe across blanket and fin-type geometries

Accurate quantification of n-type dopant, such as phosphorus (P) and arsenic (As) in silicon-germanium (SiGe), is critical for source/drain engineering, junction control, and device variability in advanced complementary metal-oxide-semiconductor. Especially for As in SiGe, conventional microanalysis techniques, such as transmission electron microscopy combined with energy dispersive x-ray spectroscopy or electron energy loss spectroscopy, struggle at technologically relevant doping levels and suffer from peak-overlap issues for As in the presence of Ge. Common secondary ion mass spectrometry (SIMS) platforms, such as magnetic sector (MS), quadrupole (Quad), and time-of-flight (ToF), face severe mass interferences at limited mass resolving power as well as low ion yields. Here, we translate the Orbitrap™-SIMS workflow, previously validated for P in Si/SiGe, to As in SiGe, combine it with self-focusing SIMS (SF-SIMS) for patterned features, and benchmark Orbitrap™-SIMS against ToF-SIMS, Quad-SIMS, and MS-SIMS. Using blanket Si1−xGex standards and patterned Ge1−y−zSiySnz:As fins, we show that the exceptional mass resolving power of the Orbitrap™ mass analyzer eliminates the dominant As interferences (e.g., As− vs GeH−; AsSi− vs GeSiH−/29SiGe−/30Si73Ge−; and AsGe− vs 73Ge76Ge−/Ge2H−) and detection limits improve by >1 order of magnitude versus ToF-SIMS and MS-SIMS when SF-relevant clusters are used. As a result, only Orbitrap™-SIMS recovers the physically correct “top-only” As-doped segment in Ge1−y−zSiySnz fins, whereas other mass analyzers erroneously report As throughout the fin due to unresolved overlaps and high backgrounds. These results are confirmed by fast Fourier transform-scanning spreading resistance microscopy 2D carrier distribution mapping.