Accurate Quantification of Si/SiGe Interface Profiles via Atom Probe Tomography

Pulsed laser atom probe tomography (APT) has enabled the investigation of semiconducting materials at sub‐nm length scales and 10 ppm chemical sensitivity. This has enabled APT to be the best technique for nanoscale detection of dopant distributions and low levels of chemical segregation at interfaces, which are both important for semiconductor processing; however, the accuracy of measured interfacial profiles is typically compromised by aberrations. Interfacial profiles in APT data will vary with respect to different interfacial combinations, especially when the evaporation field between two materials is drastically different. Here, the ability of APT to measure SiGe/Si/SiGe interfacial profiles is tested with an 8 nm Si well embedded in SiGe. The APT measurements are compared to those measured using scanning transmission electron microscopy (STEM) to evaluate reconstruction and post‐reconstruction processing methods to appropriately measure interfacial profiles using APT. Without post‐APT reconstruction processing, the measured Si/SiGe interfacial widths between APT and STEM match poorly, but after applying the z‐redistribution algorithm, the interfacial profiles are in good agreement. These results indicate that APT can be used to accurately identify SiGe/Si/SiGe interfacial profiles after application of the z‐redistribution algorithm, which will greatly impact the synergy between growth and characterization of semiconductor devices using Si/SiGe interfaces. Atom probe tomographic (APT) reconstructions are compared to aberration corrected scanning transmission electron microscopy to evaluate interfacial quality in SiGe/Si/SiGe heterostructures. It is shown that compression/expansion artifacts affecting the APT reconstructions may be largely mitigated through the use of the z‐redistribution algorithm. This allows differences in interface widths to be reliably evaluated to a precision of ≈1 Å.