Metallic conductors in an electronic chip endure mechanical stresses due to fabrication processes and also due to operating conditions such as high current densities and temperatures. The mechanical stresses and stress gradients can result in diffusion of metal ions leading to dynamic events such as void formation, growth and migration with detrimental consequences for chip reliability. The type of metals, their grain structure, the dielectrics, the material interfaces, the process conditions and also the length-scale, all have influence on stress-driven diffusive events. Due to such complexity, it is essential to develop a numerical modelling framework that enables fundamental quantitative exploration of the diffusive failure mechanisms and serve as a cost-effective predictive platform.
In this PhD project, the candidate will work towards developing continuum and discrete numerical simulation approaches to shed light on the mechanisms of stress-driven failure mechanisms in metallization at different length-scales. The candidate will have access to the existing experimental data at imec and will conduct further characterization experiments to obtain the parameters required as input for the simulations and to validate the numerical findings. This includes characterization of materials and interfaces at micro/nano length scales such as their structure, elastic, diffusive and adhesive/cohesive properties.
 P.S. Ho, Motion of inclusion induced by a direct current and a temperature gradient, Journal of Applied Physics 41 (1970) 64-68.
 M Kraatz, M Gall a, E Zschech, D Schmeisser, P.S. Ho, A model for statistical electromigration simulation with dependence on capping layer and Cu microstructure in two dimensions, Computational Materials Science 120 (2016) 29.
 H. Ceric, R.L. de Orio, J. Cervenka, and S. Selberherr, Copper microstructure impact on evolution of electromigration induced voids, Simulation of Semiconductor Processes and Devices, 2009. SISPAD '09. DOI: 10.1109/SISPAD.2009.5290222.
 Nabiollahi N., Moelans N., Gonzalez M., De Messemaeker J., Wilson C., Croes K., Beyne E., De Wolf I. (2015). Microstructure simulation of grain growth in Cu through silicon vias using phase-field modeling. Microelectronics Reliability, 55, 765-770.
 Q. M. Yu, Influence of the stress state on void nucleation and subsequent growth around inclusion in ductile material, Int J Fract 193 (2015) 43–57.
Required background: The position is best suited for candidates from mechanical engineering, material science, physics or similar disciplines preferably with strong interest and background in numerical modelling, specifically finite element modelling (FEM). Experience with a FEM software such as COMSOL, Abaqus, Marc-Mentat is of added value. Hands-on knowledge of a programming language (exp. MATLAB, C, Python, Java, etc.) is necessary. The candidate should be interested in multidisciplinary research.
Type of work: 20% literature and technological study, 60% numerical modelling, 20% experimental characterization
Supervisor: Ingrid De Wolf
Daily advisor: Houman Zahedmanesh
The reference code for this PhD position is STS1712-10. Mention this reference code on your application form.