Abstract

The main objective of this thesis is to study unique cases for computer-assisted finite element modeling (FEM) of thermal, mechanical and thermo-mechanical problems related to silicon and carbon. Computational modeling contributed to solve scientific problems either by validating the experimental results obtained earlier or by predicting the behavior of a particular system. In the model generation phase, emphasis is placed on simplification of a physical problem without loosing the validity or important details. As a consequence of reasonably reduced variables and also degrees of freedom of the elements in our models, the simulations could be performed using a commercial FEM software package, ANSYS^®.

To test the capabilities of the method (i) a steady-state finite element thermal analysis has been accomplished and verified by experiments for the case of laser-assisted heating of different materials. (ii) Mechanisms (Dember and Seebeck effects) responsible for the reduction of gold ions and deposition of metallic gold on p-type semiconductors from liquid precursors have been investigated by computing the surface temperature profiles of silicon wafers exposed to laser irradiation. (iii) Temperature field in a multi-component system caused by laser illumination was modeled to determine the heat affected zone in the case of laser soldering of flip-chips on transparent printed circuit board assemblies. (iv) Origin of the experimentally observed residual strain in thermally oxidized porous silicon structures was revealed by computing the strain fields in silicon-silicon oxide porous materials considering both intrinsic and thermal stress components. (v) Finally, we demonstrated that Joule heat generated on a silicon chip can be removed efficiently using micro-fin structures made from aligned carbon nanotubes. Computational fluid dynamics and thermal-electric finite element models were developed to study the steady-state laminar coolant flow and also the temperature distribution for the chips.

The presented novel results have potential in silicon and carbon nanotube based technologies, including deeper understanding of the processes and problems in manufacturing electronic devices.