[NanoIC topic] Advanced X-ray Scattering for the Characterization of Buried Si/SiGe Interfaces in Quantum and Semiconductor Devices

As semiconductor devices continue to scale toward the angstrom regime, the properties of buried Si/SiGe interfaces become increasingly critical for device performance and production. This is particularly relevant for emerging technologies such as semiconductor spin qubits [1] and the complementary FET (CFET) [2], where interface morphology directly influences carrier confinement, roughness scattering and device-to-device variability. In this context, the development of advanced metrology techniques capable of probing angstrom-scale interface properties in a non-destructive and accurate manner is essential.

This internship focuses on the use and further development of X-ray reflectivity (XRR) and high-resolution X-ray diffraction (HR-XRD) [2], as well as extended X-ray scattering methods for the characterization of buried interfaces [3]. These methods provide access to roughness and intermixing of numerous interfaces in complex multilayer systems. The work will involve both the acquisition and analysis of X-ray spectra, using laboratory-scale tools as well as synchrotron-based experiments. The scattering results will be benchmarked against established yet destructive reference metrology techniques, such as atom probe tomography (APT) [2] and transmission electron microscopy (TEM) [4].

The student will join imec’s team of experts in metrology and material characterization for solid-state technology. The internship will start with an introduction to the physics of interfaces and the principles of X-ray reflectivity and scattering. The student will then focus on the analysis and interpretation of spectra measured on simple few-layer samples. Based on their interests, the internship can evolve toward theoretical modelling and spectral simulation or toward the experimental analysis of X-ray spectra or reference (APT/TEM) measurements of more complex samples.

We seek a candidate with a background in physics or materials science, and a strong interest in both experimental work and theoretical interpretation. The ideal candidate is analytical, meticulous, and comfortable with mathematical concepts. A solid basis in quantum mechanics, statistics and measurement uncertainty theory is appreciated. This internship offers hands-on experience with state-of-the-art metrology, exposure to cutting-edge semiconductor research, and insight into the interplay between material interfaces and device performance.

References:

[1] Paquelet Wuetz, B. et al. (2022). Atomic fluctuations lifting the energy degeneracy in Si/SiGe quantum dots. Nat Comm, 13(1), 7730. https://doi.org/10.1038/s41467-022-35458-0

[2] Bogdanowicz, J. et al. (2025, April). Inline x-ray metrology for complementary field-effect transistors (CFET). In Metrology, Inspection, and Process Control XXXIX (Vol. 13426, pp. 326-332). SPIE. https://doi.org/10.1117/12.3050810

[3] Headrick, R. L., & Baribeau, J. M. (1993). Correlated roughness in (Ge m/Si n) p superlattices on Si (100). Phys Rev B, 48(12), 9174. https://doi.org/10.1103/PhysRevB.48.9174

[4] Paysen, E. et al. (2024). Three-dimensional reconstruction of interface roughness and alloy disorder in Ge/GeSi asymmetric coupled quantum wells using electron tomography. ACS Appl Mat & Int, 16(3), 4189-4198. https://doi.org/10.1021/acsami.3c15546