Thesis presented November 09, 2010
Abstract:
The aim of this thesis is an experimental study of the fracture stage of the Smart CutTM thin layer transfer process, which is based on the implantation of light ions in a crystalline matrix. Several experimental tools have been built-up for that purpose: an interfacial gas quantification apparatus, a crack velocity measurement bench, and an
in-situ temperature microscopy set-up. The localized hydrogen implantation weakens a silicon wafer: the induced modifications of its mechanical properties have been quantified. The microcracks that develop in the implanted region during annealing can be modelled by the theory of linear elastic fracture. The evolution of their population is due to coalescences, and results in a reduction of their density simultaneously to an increase of their mean radius. This development is permitted by the precipitation of part of the implanted hydrogen in these pressurized cavities under gaseous form. Their filling is carried out through a vertical collection of atomic hydrogen, involving one third of the total dose at the end of the annealing. The kinetics of this micro-cracking of the interface is driven both by the hydrogen diffusion and crack growth mechanics. In a final step, the material breaks at the weakened area. Then, a fracture opens the entire interface at a speed of several km/s, which has been measured as a function of different experimental parameters and modelled. The interaction between this fracture tip and microcracks alter the surface state of the transferred film.
Keywords:
Fracture dynamics, Cracking, fragility, ion implantation, fracture surfaces, gas precipitation