[NanoIC topic] X-ray Characterization of Micron-thick Multilayers for Next-generation Memory Devices

As the rapid expansion of artificial intelligence (AI) drives demand for higher-capacity memory solutions, the semiconductor industry is exploring novel memory architectures beyond conventional DRAM. The most promising approach is 3D-DRAM, where memory cells are vertically stacked to substantially increase storage density [1]. A key building block of these architectures is the fabrication of thick multilayer structures, consisting of repeated ONO (SiO₂/SiNx) [2] or Si/SiGe [3] layer pairs. As these stacks grow from tens to nearly one hundred bilayers and thus reach a total thickness of several micrometers, precisely controlling layer thickness and interface quality becomes challenging due to strain [3]. Thickness and interface variations may propagate throughout the stack and ultimately lead to nonuniform devices.

This internship focuses on the development of advanced X-ray techniques to characterize the thick multilayer structures occurring in future 3D-DRAM technologies [4,5]. In particular, the work will employ X-ray reflectivity (XRR) and High-resolution X-ray diffraction (HR-XRD) to quantify multilayer periodicity, individual layer thicknesses, and interface quality throughout the stack. In addition, synchrotron-based grazing-incidence small-angle X-ray scattering (GISAXS) and diffuse scattering measurements will be used to investigate interface waviness and correlations between buried interfaces [4]. These techniques provide unique non-destructive access to deeply buried layers, overcoming limitations of conventional optical and electron microscopy methods [2,5]. The X-ray results will be benchmarked against established reference techniques such as transmission electron microscopy (TEM).

The student will join imec's team of experts in metrology and materials characterization for advanced semiconductor technologies. The internship will start with exploring X-ray characterization techniques and the material systems. Then, the student will focus on the analysis and interpretation of lab-scale X-ray spectra acquired from ONO and Si/SiGe samples with varying layer thickness, stack heights and interfaces. Finally, complementary spectra are collected with high counting statistics during a synchrotron beamtime. The precise content of the project will be aligned with the interests of the student.

We seek a candidate with a background in physics, materials science, nanotechnology, or a related field, and a strong interest in experimental work, data analysis and theoretical interpretation. The ideal candidate is analytical, meticulous, and comfortable with mathematical concepts. Basic familiarity with X-ray techniques, data analysis, statistics, or scientific programming is appreciated but not required. This internship offers hands-on experience with state-of-the-art metrology, exposure to cutting-edge semiconductor memory research, and insight into the relationship between multilayer growth, interface morphology, and the future scaling of 3D-integrated memory technologies.

References:

[1] Belmonte, A., & Kar, G. S. (2025). Disrupting the DRAM roadmap with capacitor-less IGZO-DRAM technology. Nature Reviews Electrical Engineering, 2(4), 220-221. https://doi.org/10.1038/s44287-025-00162-w

[2] Kwak, H., et al. (2021). Non-destructive thickness characterisation of 3D multilayer semiconductor devices using optical spectral measurements and machine learning. Light: Advanced Manufacturing, 2(1), 9-19. 10.37188/lam.2021.001

[3] Loo, R., et al. (2025). Epitaxial growth of up to 120×{Si0. 8Ge0. 2/Si} bilayers in view of three-dimensional dynamic random access memory applications. Jour of App Phys, 138(5). https://doi.org/10.1063/5.0260979

[4] Siffalovic, P., Jergel, M., & Majkova, E. (2011). GISAXS-probe of buried interfaces in multilayered thin films. X-ray Scattering, 1-54.

[5] Ming, Z. H., et al. (1993). Microscopic structure of interfaces in Si_{1− x}Ge_x/Si heterostructures and superlattices studied by x-ray scattering and fluorescence yield. Phys Rev B, 47(24), 16373. https://doi.org/10.1103/PhysRevB.47.16373