Research & development - Leuven | More than two weeks ago
The ever-ongoing downscaling of semiconductor technology has led to a paradigm shift from planar to 3D devices. Industry has moved towards 3D architectures such as fin field-effect transistors, with next being nanosheets and nanowires on the roadmap for their better electrostatic control and reduced power dissipation . Additionally, novel material systems are constantly being investigated to improve or even disrupt conventional CMOS technology with the introduction of entirely new concepts – think of 2D materials, systems portraying (topologically) protected states, or phases which exhibit exciting superconducting, spintronic, thermoelectric or ferroelectric properties, etc.
The performance of such nano-applications is tailored by the structure and chemical composition at the atomic level: a few displaced atoms can make the difference! Device fabrication and characterization has never been so challenging, as tomorrows nano-devices become increasingly complex, and new materials and ingenious fabrication processes that continue to unfold. Hence, a reliable 3D characterization technique with close to atomic resolution and high elemental sensitivity is not only a dream – it is a requirement!
Laser-assisted atom probe tomography (L-APT) has emerged as the promised solution. In a nutshell (Fig. a), L-APT is based on the concept of controlled field emission of atoms from a needle-shaped specimen by a time-resolved laser pulse with the mass (hence element) identification achieved through the ions’ time-of-flight. By collecting the ions on a 2D detector and tracking their arrival sequence, we can reconstruct the 3D volume of the analyzed sample with sub-nm resolution (Fig. b).
While L-APT offers promise, many challenges have yet to be solved. These challenges arise mainly from the underlying physics, where one must understand e.g., the short-pulsed laser interaction with a nanoscale tip, the field evaporation behavior of surface atoms in a heterogeneous system, atomic processes (diffusion) on the surface and during the ion’s flight sequence (molecular ion dissociation), etc. – all of which might intricately contribute to a faulty composition and/or element distribution being measured. Understanding these physical mechanisms and identifying their driving forces will bring us closer to a true, quantitative 3D nanoscale characterization method for future materials and devices.
In this project you will work with state-of-the-art APT equipment. You will have the possibility to explore a vast playground of experimental work, data reconstruction and analysis, and literature available in this field of research.
 W. Vandervorst et al., “Dopant, composition and
carrier profiling of 3D structures”, Mater Sci Semicond Process 62, 31
 A. Veloso et al., "Vertical Nanowire and Nanosheet FETs: Device Features, Novel Schemes ...." IEEE IEDM,11.1.1-11.1.4, (2019)
Type of project: Thesis
Duration: Whole academic year for master thesis
Required degree: Master of Science
Required background: Physics, Nanoscience & Nanotechnology
Supervising scientist(s): For further information or for application, please contact: Jeroen Scheerder (Jeroen.Scheerder@imec.be)
Only for self-supporting students.