As we are rapidly approaching the physical scaling limits of Si, the Si era will end soon and a (r)evolution is required to keep up with the continuous demand for faster electronics operating at lower power and with more functionality. Not only will Si be replaced, but a whole new set of materials, novel device architectures and fundamentally different device concepts need to be introduced in future devices, preferably at a high pace.
For instance, regarding materials, one is looking at very thin, high mobility materials, such as graphene and transition metal dichalcogenides (TMDs), to boost the performance of future transistors. Another example is the transition from Si to GaN for power devices, where GaN has superior switching and lower leakage behavior. Novel architectures such as magnetic tunnel junctions (MTJ) or InGaZnOxide (IGZO’s) based transistors present a radical change from the current Si based transistors. The recent discovery of ferroelectricity in binary oxides such as doped HfO2 and ZrO2 has renewed the interest for ferroelectric-based nanoelectronics.
Obviously, adequate metrology is required to gain fundamental understanding on these new concepts and materials. As an intrinsic high-resolution two-dimensional (and 3D) technique, Scanning Probe Microscopy (SPM) has been identified as a key characterization technique for investigating these new materials and concepts at the nanoscale. Therefore, the materials characterization department is looking for an ambitious Phd-student willing to plunge into the world of SPM and explore the limits of current electrical SPM characterization, and develop new modes (C-AFM, STM, MFM, PFM and applications for harvesting fundamental information on these novel materials.
As a first objective, we are striving to probe and understand the conduction mechanisms of materials such as TMDs, IGZO, GaN, MTJ at the nanoscale. These are potential candidates for future high mobility (high power) channel devices and it is crucial to investigate the impact of grain boundaries on the current conduction, to understand what the role is of defects, composition, interfaces, doping, etc, on the electrical properties. For instance, in TMDs the mobility is still well below the expected values, while in IGZO and GaN materials, the dopant (de-)activation mechanisms are still unknown. Furthermore, as these new materials have drastically different crystallographic and mechanical properties, it will also be crucial to understand the probe-material interaction, the second objective. Whereas for Si and Ge this is already known in detail, fundamental knowledge is missing for these advanced materials.
The third objective is to go beyond the pure electrical properties and to investigate the magnetic and piezo-electric properties of such materials, an example are the ferromagnetic materials in an MTJ stack or the binary oxides in a memory stack. The challenge here will be to probe the magnetic and piezo electric behavior, and similarly as in the first objective, to determine and study the effect of grain boundaries, defects, morphology, composition.
By taking on these challenges the candidate will be at the forefront of future devices and materials, and he will be exposed to multiple programs at imec, a wide variety of experts and the large scala of complementary metrology tools at imec.
Required background: physics, engineering technology, engineering science or equivalent
Type of work: 70% extensive experimental work linked with 30% theoretical understanding
Supervisor: Wilfried Vandervorst
Daily advisors: Kristof Paredis, Umberto Celano
The reference code for this PhD position is STS1712-52. Mention this reference code on your application form.