Defense of the doctoral thesis of Dimitrios DAMIANOS, for the University Grenoble Alpes, speciality " NANO ELECTRONICS & NANO TECHNOLOGIES ", entitled:
Amphi M001 - Phelma/Minatec 3 rue parvis Louis Néel 38016 Grenoble cedex1
«Second harmonic generation (SHG) for contactless characterization of dielectric-semiconductor interfaces »
Wednesday, October 3rd, 2018 at 14:00
This PhD work was developed in the context of research for novel characterization methods for ultra-thin dielectric films on semiconductors and their interfacial quality. Second harmonic generation (SHG) is a very promising non-invasive technique based on nonlinear optics. A laser emitting at the fundamental frequency is incident upon the sample which responds through its 2nd order polarization, generating a signal at twice the fundamental frequency. For centrosymmetric materials such as c-Si, amorphous SiO2 or Al2O3, the SHG signal is mainly due to the defects and to the static electric field Edc present at the interface (due to pre-existing charges Qox and/or photo-injected charge trapping/detrapping at interface traps Dit). Thus, SHG measurement gives access to the quality of dielectric/semiconductor interfaces. Nevertheless, the SHG signal is also dependent on multilayer optical propagation phenomena. For this reason, we have developed a simulation program which accounts for the optical phenomena and the static electric fields at the interfaces. We have used SHG to monitor the passivation quality of Al2O3/Si structures prepared with different processes and showed a correlation between SHG and minority carrier lifetime measurements. Qox and Dit were extracted from capacitance-voltage measurements and helped calculating the Edc values. The optical simulation, fed with known Edc values reproduced the experimental SHG data in these structures. The SHG was also used for Silicon-on-Insulator (SOI) substrates characterization. In thick SOI structures, both simulations and experimental results show that the SHG response is mainly given by optical interferences (Edc has no impact). In ultrathin SOI, the interfaces are electrically coupled and Edc is needed as input in the simulation in order to reproduce the experimental SHG data. This implies that in ultrathin SOI, SHG can access the interface electric fields in a non-destructive way.
Members of jury :
Anne KAMINSKI-CACHOPO : Supervisor
Irina IONICA : Co- supervisor
Daniele BLANC-PELISSIER: Co- supervisor
Olivier PALAIS: Reviewer
Yves JOURLAIN : Reviewer
Jean-Pierre RASKIN : Examiner
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Thesis prepared in the laboratory : UMR 5130 - Institut de Microélectronique, Electromagnétisme et Photonique -Laboratoire d'hyperfréquences et de caractérisation , supervised by KAMINSKI-CACHOPO Anne, supervisor and IONICA Irina, Co-supervisor.