3D materials characterization for next generation devices

At imec, we are in the unique position to develop metrology and 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].

In the context of 3-dimensional materials characterization, Atom Probe Tomography (APT) has recently appeared on the semiconductor landscape [3]. This 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. APT perfectly bridges the gap between Transmission Electron Microscopy (TEM) and Secondary Ion Mass Spectrometry (SIMS), offering a better sensitivity (i.e. lowest detectable concentration) as TEM does, and a higher spatial resolution than SIMS. When being applied to semiconductor devices, APT is however a far less mature characterization method, which holds plenty of 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 PhD project, you will tackle reliability aspects of Atom Probe analysis with strong focus on mechanical failure mechanisms. For APT, the sample is prepared into a mm 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 (ns) laser pulses at ~200kHz frequency. These experimental conditions lead in some material systems 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.

The access to state-of-the-art equipment (APT LEAP5000XR, Invizo6000) and material systems of varying complexity, will enable you to study experimentally the relationship between material properties (microstructure, defectivity, interface properties), sample preparation strategies, experimental conditions, and failure mechanisms. You will also have access to complementary materials characterization (e.g. TEM, SEM) and mechanical testing, and you can draw on the extensive expertise available at imec in the field of materials characterization (including APT), material science, mechanical testing, reliability and simulation. Depending on your interest, this project could be complemented with multi-physics simulations. Ultimately, the outcome of your project will increase 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)