PhD Defense of Baydaa OBEID

Keywords :  
Second harmonic generation (SHG), passivation, interface electric field, fixed oxide charges, interface traps, capacitance-voltage (C-V).


Abstract: :
The performance of devices such as MOSFETs, image sensors, photovoltaic cells is dramatically influenced by the quality of interfaces, in particular between dielectrics and silicon. Passivation of Si using high-k dielectrics is known to improve the electrical properties of these interfaces. Among the methods used to characterize passivation, the second harmonic generation (SHG) is a promising sensitive and non-destructive technique based on the nonlinear optics. In the dipole approximation, the bulk SHG response is zero in centrosymmetric materials (e.g. Si, Al2O3, SiO2, etc.), therefore the SHG response mainly contains interface-related information, where the symmetry is broken. Additionally, when an electric field (EDC) exists at the interface, the signal is reinforced by the so-called EFISH (electric field induced SHG). Since the interface electric field is related to fixed oxide charges (Qox) and/or interface states (Dit), the SHG technique is sensitive to these electrical parameters. The aim of this thesis is to calibrate the SHG response for EDC measurement, particularly associated with Qox in the dielectrics. Extracting electrical-related information from SHG experimental data necessitates taking into account the influence of optical phenomena (absorption, interferences, etc.), which was achieved thanks to modeling/simulation of the nonlinear second harmonic response. Our simulation program is based on theoretical models from the literature that we adapted for multilayers. The experiments were performed on several Al2O3 layers on Si (100), deposited in different conditions and that exhibit very different interface quality. Complementary electrical techniques, such as corona oxide characterization of semiconductor (COCOS) and capacity-voltage measurements (C-V), gave access to the electrical field of the samples and complete the SHG results for the calibration. Both experiments and simulations prove the possibility of calibration for monolayers of dielectric on Si. Some challenges related to the characterization of multilayers such as silicon on insulator (SOI) are also discussed, in particular the influence of the layer thicknesses and of the electric fields of various nonlinear interfaces on the SHG response.

Jury members :

• Prof. Georges BREMOND, , INSA Lyon : Reviewer
• Prof. Yannick DUMEIGE, Université Rennes 1 : Reviewer
•  Prof. Anne KAMINSKI, Grenoble INP - UGA : Examiner
• Dr. Sébastien DUBOIS, Commissariat à l'énergie atomique (CEA) : Examiner
• Dr. Delphine Le Cunff, STMicroelectronics  : Guest
• Dr. Guy Vitrant, Grenoble INP - UGA : Guest

Supervisors:

• Dr. Irina Ionica, Grenoble INP - UGA : Supervisor
•  Dr. Lionel Bastard, Grenoble INP - UGA : Co-supervisor