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Advanced characterization of HEMT transistor interfaces for power electronics: correlation between chemical, structural and electrical properties

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Date Limite Candidature : jeudi 19 août 2021

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General information

Reference : UMR8180-MURBOU-002
Workplace : VERSAILLES
Date of publication : Thursday, June 17, 2021
Scientific Responsible name : Muriel Bouttemy
Type of Contract : PhD Student contract / Thesis offer
Contract Period : 36 months
Start date of the thesis : 1 October 2021
Proportion of work : Full time
Remuneration : 2 135,00 € gross monthly

Description of the thesis topic

The gallium nitride (GaN) sector is strategic as, in particular, it represents an interresting route to improve the power and efficiency of radar systems with active antennas and electronic warfare systems. This technology will make it possible to cover the millimeter wave range up to an operating frequency of 94 GHz, and will therefore open up a field of applications of new functions unprecedented in the military field (such as active antenna radars operating on the 8-40 GHz frequency bands for target detection), than for civilians such as future 5G telecommunications. It is important to note that no GaN technology delivering high power above 40 GHz is currently available globally. The main limitations are the added power efficiency (PAE), the control of trap effects as well as the reliability of this type of components with a sub-150 nm gate. This project entitled GREAT ("High frequency GaN electronic") brings together academic laboratories and two industrial partners (UMS and SOITEC) and will therefore contribute to the emergence of new technology in this strategic area.
The subject of this thesis falls within this context and capitalizes on the results of preliminary studies, particularly within the national network Labex GaNeXT, and on the methodological achievements of the ILV laboratory in Versailles (Lavoisier Institute of Versailles) where will largely take place this thesis. It will take place jointly with the IEMN laboratory in Lille (fabrication of structures and components with / without electrical stress, electrical characterization, preparation of FIB lamellas) and in collaboration with the C2N in Palaiseau (preparation of FIB lamellas, TEM / STEM). This thesis is dedicated to the analysis of materials and components generated as part of the GREAT project. It will aim to develop a new robust chemical and structural analysis methodology where localized probe Auger spectroscopy is the central technique (5 nano-probes in France). The work will focus, in particular, on the analysis of metal / semiconductor, passivation / semiconductor interfaces and between passivation layers, in order to improve the electrical performance of these devices. Indeed, most of the issues related to the degradation mechanisms of GaN transistors lie in the degradation of interfaces that have undergone an electric field peak and / or a temperature peak. Likewise, the leakage currents as well as the trapping mechanisms located on the surface of the components are directly linked to the chemical states located at the passivation / semiconductor interface. The challenge lies in accessing the various critical areas that influence the component's electrical response and performance, which is essential to better understand the physico-chemistry of the interfaces of these components.

The program of this thesis is divided into 4 research axes:
1- Development of a sample preparation method to access areas of interest while preserving their chemical and structural integrity
Different preparation methods will be evaluated to access the interfaces from the surface and in direct cross-section access. Important work will be done on the FIB preparation.
2- Calibration of the Auger chemical analysis (quantification of the results and determination of the chemical environment)
This calibration will be carried out using a multi-technical approach (XPS, SIMS, STEM-EDS, etc.)
3- Determination of the capacities and sensitivity of Auger to provide information on the chemistry of surfaces and interfaces and correlation with electrical measurements
This will involve testing this methodology on concrete cases made up of defined test structures (technological variants and different electrical stresses).
4- Application of this methodology to help in the understanding of the drift observed on real cases of GaN component resulting from the GREAT project and the industrial partner.

The first two axes are essential to ensure the reliability of the data obtained before using the Auger as a localized probe on test and real components.

• Skills to be acquired during the thesis:
- Theory and practice of Auger and XPS electron spectroscopies
- Theory and use of SIMS data analyzes
- Ion beam / material interaction (preparation of cross sections by FIB lamellas and ion polisher)
- Theory and exploitation of TEM and STEM analyzes
- Electrical characterizations of components (measurements in static and dynamic conditions of transistors: IV DC and pulsed, S parameters, power, gain; PAE)
- Project management and presentation of results orally and in writing (project meetings and presentations at conferences)

• Skills required :
- Analytical Chemistry
- Physical chemistry of materials
- Microelectronics
- English proficiency

Work Context

This thesis (Université Paris-Saclay) will be carried out jointly between ILV and IEMN, with C2N and 2 industrial partners as another privileged academic partner. The thesis will mainly take place at ILV but the doctoral student will have to travel between these three laboratories.
The Lavoisier Institute of Versailles (http://www.ilv.uvsq.fr/) is a Joint UVSQ-CNRS Research Unit (University of Versailles-Saint Quentin). The laboratory staff are 100 people divided into 3 research teams: 54 permanent staff (10 CNRS researchers, 8 ITA CNRS, 33 UVSQ teacher-researchers, 3 BIATSS UVSQ, 1 DR CNRS emeritus, 1 invited DR, 4 doctoral students, post -doctoral fellows and ATER). This UMR is characterized by its multidisciplinarity, exploring very diverse themes, which range from the chemistry of molecular or porous materials (MIM_Molecules, Interactions and Materials team), to synthetic organic chemistry (SORG_Synthèse Organique team), including interfacial electrochemistry (EPI_Electrochimie Physico-chimie aux Interfaces team). Three key words therefore characterize the unit: synthesis (semiconductor, organic, porous, inorganic molecular materials, etc.), properties (physicochemical, biological, catalytic, etc.) and analysis. This thesis will take place within the EPI team and will benefit from the characterization hub of CEFS2 (electron spectroscopies center), attached to the group.

The Institute of Electronics, Microelectronics and Nanotechnology (IEMN) brings together in a single structure most of the regional research in a vast scientific field ranging from nanosciences to instrumentation.
Making researchers with different cultures, approaches and motivations work together, building a continuity of knowledge ranging from fundamental problems to applications is our specificity today. Today, nearly 500 people, including around 100 international researchers, work together.
The heart of our activities is centered on micro and nanotechnologies and their applications in the fields of information, communication, transport and health. Our researchers have at their disposal exceptional experimental resources, in particular technology and characterization plants, the possibilities and performance of which are at the best European level. The IEMN is part of the network of large RENATECH technology centers.
Our scientific policy consists not only in the deepening of knowledge but also in the establishment of a privileged partnership with industrial leaders in their markets and in the development of a close partnership with regional mid-cap companies and SMEs and young shoots from of the IEMN.

The Center for Nanosciences and Nanotechnologies (C2N) is a joint research unit between the CNRS and the University of Paris-Saclay, which has more than 380 members. Born from the merger of the Laboratory of Photonics and Nanostructures (LPN) and the Institute of Fundamental Electronics (IEF), the laboratory moved to a new building in the heart of the Paris-Saclay Campus in 2018.
Its creation is part of an ambitious perspective. The laboratory benefits from the very favorable location of the Plateau de Saclay, for exchanges with academic laboratories and with the R&D of the local industrial pole. It brings together critical forces on key research axes and meets two main inseparable objectives: (i) create a flagship laboratory for research in nanosciences and nanotechnologies; (ii) provide the Saclay plateau and the Ile-de-France region with a large technological infrastructure, open to all academic and industrial players in the field, particularly those in the Paris region. C2N includes four research departments: Photonics, Nanoelectronics, Materials, Microsystems and Nanobiofluidics. Exploring physics and technology at the nanoscale, the laboratory combines fundamental and applied research for short to medium term applications.

Constraints and risks

Afin de bénéficier des compétences et savoir-faire des aux 3 laboratoires, ILV, IEMN et C2N, des déplacements sont à prévoir entre ces 3 sites.

Cette thèse s'inscrit dans le cadre d'une convention entre DGA et CNRS sur un projet de recherche qui inclut 2 partenaires industriels. Des règles de confidentialité seront donc à respecter.

Additional Information

In order to benefit from the skills and know-how of the 3 laboratories, ILV, IEMN and C2N, travel should be planned between these 3 sites.
This thesis is part of an agreement between DGA and CNRS on a research project that includes 2 industrial partners. Confidentiality rules will therefore have to be respected.

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