When Nano-Needles Break: Investigating Failure Mechanisms in Atom Probe Tomography

At imec, we are in the unique position to develop materials characterization solutions for the future generation semiconductor technologies. Often overlooked, this is a crucial component in achieving the ambitious goals depicted on our roadmap [1,2].

Atom Probe Tomography (APT) is an exciting 3-dimensional materials characterization technique that has recently appeared on the semiconductor landscape [3]. This state-of-the-art method is very valuable to reveal for example dopant distributions in a gate-all-around nanosheet transistor, local composition fluctuations in a SiGe spin qubit, interface diffusion in a magnetic random access memory device, etc. However, when being applied to semiconductor devices, APT is still a very novel characterization method, with many opportunities for impactful research and development aspects around the underlying physical mechanisms, automation approaches, 3D data reconstruction protocols, statistical data analysis schemes and many more.

In this project, you will tackle the challenge of mechanical failure of specimen during Atom Probe analysis. For APT, specimen are prepared into a micrometer long needle with an endpoint radius of less than 50 nm. During APT data acquisition, this needle is being held at cryogenic temperatures while being exposed to a standing voltage of ~10 kV coupled with ultra-short (ps) laser pulses at ~200 kHz frequency. These conditions induce cyclic mechanical and thermal stresses, which in some material systems lead to premature fracture of the needle before any data can be recorded. You shall identify the root-causes for these failures and propose innovative solutions to mitigate them for a well-defined set of material systems. This work will benefit from a strong multidisciplinary and out-of-the-box mindset, as it touches on aspects of high-field physics, material science, mechanical properties of materials, interface physics, etc.

This internship is embedded in the Atom Probe Tomography (APT) research group at imec. Depending on the state of the ongoing research and the background and interests of the candidate, the project may focus on APT experimental work, correlative studies combining APT with advanced complementary characterization such as transmission electron microscopy or micromechanical testing, or data-mining approaches aimed at uncovering previously hidden correlations governing APT specimen yield. The access to state-of-the-art equipment and material systems of varying complexity will enable you to study the relationship between material properties (microstructure, defectivity, interface properties), specimen preparation strategies, experimental conditions, and failure mechanisms.

Ultimately, the aim is to broaden the application range of APT, allowing us to better leverage the strength of this 3D characterization method. Speeding up our learning cycles will be beneficial for the development of the next generation devices and the achievement of the ambitious goals of the semiconductor industry.

[1] https://www.imec-int.com/en/articles/20-year-roadmap-tearing-down-walls

[2] Mary A. Breton, et al., J. Micro/Nanopattern. Mats. Metro. 21(2) 021206 (2022)

[3] B. Gault, Nature Reviews Methods Primers volume 1, 51 (2021)  

Required background: Materials science and engineering, Physics with a strong focus on solid state physics