Laser processes on surfaces in femtosecond domain

In this thesis we investigated the interaction between ultrafast pulses (<_ 10 ps) and nanometric dielectric surfaces. The study of the interaction between this kind of pulses and matter has a great importance in many types of application, principally for the reduced thermal effects and for the high precision achievable in the realized structures. Particularly, our work was interested in the solar industry application where an ultrafast laser source can be used to open the contacts in the passivation layer which covers the back side of the PERC solar cells. The study involved the characterization of the process in function of the surface, pulse length, different wavelengths and different average intensity. Subsequently the processed samples analysis with the use of SEM and EDX. The results have demonstrated that the removal of dielectric material can happen due to direct or indirect ablation and has highlighted the regimes in which there is a clean and precise delamination of the material without damaging the silicon substrate. This study was realized thanks to the collaboration between Università degli Studi di Padova and Applied Material Italia that has financed the project and, especially, cared for the production and the testing of solar cells