PhD - Leuven | More than two weeks ago
The performance improvement at every new technology node increasingly encounters constraints in access resistances and overall conductivity within various components of the device. For that purpose, various solutions to improve dopant activation and/or more specifically layer conductivity are investigated. These encompass alternative technologies (laser anneal, co-doping) leading to improved dopant activation, stress engineering for enhancing activation as well as higher carrier mobility and exploiting new high-mobility materials (Ge, SiGe, III-V) again for improving mobility and thus conductivity. The reduced dimensionality of future devices creates additional difficulties due to the dramatically different surface/volume ratio’s (changing the relative concentrations of dopant atoms versus interstitials and vacancies which impacts on diffusion and activation), the ubiquitous presence of the surface (causing loss of dopants by surface migration), non-uniform strains and reduced dimensions (impacting on bandgap and thus activation etc.). Since all these devices moved from planar to three-dimensional architectures with very limited volumes, the metrology approaches used to determine dopant activation and incorporation as well as strain are severely challenged as well.
This project aims at tackling these
critical issues by a global approach whereby advanced 3-dimensional metrology
is exploited and optimized concurrently with the development of a fundamental understanding
of the different aspects involved.
The project targets investigating the use of Atomprobe tomography to probe the dopants in confined volume with near atomic scale resolution. This may require further improvements and understanding of the APT technique itself to meet the required precision, spatial and quantification accuracy. Moreover, advanced data algorithms (e.g. cluster analysis) may be required to extract the dopant clustering as a source of dopant deactivation. The experiments are to be underpinned by simulations of the field emission process in Atomprobe tomography to unravel the atomic mechanisms at play (e.g. clustering, dissociation). Ultimately, this will shed more light on potential measurement artefacts and root-causes of deteriorated spatial resolution and erroneous quantification, as often observed in Atomprobe tomography. To this end, emphasis will be set on the development of realistic atomistic models and innovative multi-physics approaches to capture the complexity of the field emission process on the modelling side.
Further on, these studies are to be complemented by metrology probing the electrical activation and carrier density using for instance Scanning Probe Microscopy (SSRM, C-AFM, KPFM). As SPM is inherently 2D, the exploration of 3D-devices (nanowires, nanosheets,..) requires the use of the Scalpel technique whereby SPM-tips are also used to remove (on the atomic scale) material thus essentially creating a three-dimensional probing concept. For the Strain metrology into confined volumes you will collaborate with experts in (Tip-enhanced) Raman Spectroscopy and Transmission Electron Microscopy. Ultimately the correlation will be used to explain the electrical behavior of various technologies implement into dedicated test structures such that their electrical properties can be determined relative to a complete device to understand the impact of the contact geometry and of the confinement on the free carriers and currents inside the investigated structures.
This work will be done in the characterization group of imec in conjunction with activities within the modelling group. The results are of relevance for multiple projects at Imec and of high relevance for many of its industrial partners.
Required background: Physics, engineering technology, engineering science, Nanoscience, Nanotechnology or equivalent
Type of work: 40% Experimental, 30% Modeling/Simulation, 30% Theoretical
Supervisor: Claudia Fleischmann
Co-supervisor: Geoffrey Pourtois
Daily advisor: Jeroen Scheerder, Richard Morris
The reference code for this position is 2021-007. Mention this reference code on your application form.