Low temperature selective epitaxial growth of SiGe(:B) for pMOS FD-SOI transistors
As silicon technologies for microelectronics continue to evolve, processes involved in device manufacturing need to be optimized. More specifically, epitaxy, a crystal growth technique, is being used to fabricate 10 nm technological node FD-SOI (Fully Depleted-Silicon On Insulator) transistors as part of CEA-Leti's NextGen project. Doped and undoped Si and SiGe semiconductor epitaxy is being developed to improve the devices' electrical performances. The thesis will focus on selective SiGe(:B) epitaxy for channels and source/drains of pMOS transistors. A comparison of SiGe and SiGe:B growth kinetics will be made between growth under H2, the commonly used carrier gas, and N2. Innovative cyclic deposition/etching (CDE) strategies will also be evaluated, with the aim of lowering process temperatures.
Advanced Surface Analysis of Ferroelectrics for memory applications
CEA-Leti has a robust track record in memory technology. This PhD project aims to contribute to the development of HfO2-based ferroelectric devices. One of the major challenges in this field is to stabilize the orthorhombic phase while reducing film thickness and thermal budget. To gain a deeper understanding of the underlying mechanisms, a novel sample preparation method will be adapted from a previous PhD project and further developed for application to ferroelectric memories. This method involves creating a beveled crater that exposes the entire thickness of the film, allowing for access by multiple characterization techniques (XPS, TOF-SIMS, SPM) on the same area. This approach will enable the correlation of compositional and chemical measurements with electrical properties. Furthermore, heating and biasing within advanced surface characterization instruments (TOF-SIMS, XPS) will provide insights into how device performance is influenced by compositional and chemical changes.
You possess strong experimental skills and a keen interest in state-of-the-art surface analysis instruments. You excel in team environments and will have the opportunity to collaborate with experts across a wide range of techniques on the nanocharacterization platform, including advanced numerical data treatment. Proficiency in Python or similar programming languages is highly desirable.
ALD materials for FE and AFE capacitances
Ultrathin HfO2-based materials are regarded as promising candidates for embedded non-volatile memory (eNVM) and logic devices. The CEA-LETI has a leadership position in the field of BEOL-FeRAM memories ultra-low consumption (<100fj/bit) at low voltage (<1V). In this context, the developments expected in this thesis aim to evaluate the impact of HfO2-based ferroelectric FE and antiferroelectric AFE layers (10 to 4 nm fabricated by Atomic Layer Deposition ALD) on the FeRAM properties and performances.
In particular, the subject will permit a deep understanding of the crystallographic phases governing the FE/AFE properties using advanced measurements techniques offered by the CEA-LETI nano-characterization platform (physico-chemical, structural and microscopy analysis, electrical measurements). Several integration solutions for ferroelectric capacitances FeCAPs using ALD FE/AFE layers will be studied including doping, interface layers, sequential fabrication w/wo air break…
Thus, the developments based on FeCAPs stack fabricated using 300mm ALD deposition tool aspires to explore the following items:
1-Doping incorporation in FE/AFE layers (La, Y…)
2-Engineering of the interface between FE/AFE layers and top/bottom electrode
3-Plasma in-situ treatment of bottom electrode surface
4-Sequential deposition with and without air break
[1] S. Martin et al. – IEDM 2024
[2] Appl. Phys. Lett. 124, 243508 (2024)
Digital reconstruction of an industrial tank for the improvement of real-time monitoring instrumentation
In the context of industrial digitalization and real-time monitoring, accessing 3D fields (velocity, viscosity, turbulence, concentration, etc.) in real time can be crucial, as local sensor networks are sometimes insufficient to provide a comprehensive view of the system's dynamics. This PhD project aims to investigate a methodology for the real-time reconstruction of fields within an instrumented industrial tank equipped with a mixing system. The proposed approach relies on finite element modeling of the relevant physics within the tank (e.g., fluid dynamics, thermal processes) and model reduction techniques such as physics-based Machine Learning (virtual sensor approach). A key focus of this thesis will also be the development of the tank instrumentation and its associated acquisition chain, both to validate the models and to generate a database for applying the proposed methodology.
Enhanced Quantum-Radiofrequency Sensor
Through the Carnot SpectroRF exploratory project, CEA Leti is involved in radio-frequency sensor systems based on atomic optical spectroscopy. The idea behind the development is that these systems offer exceptional detection performance. These include high sensitivity´ (~nV.cm-1.Hz-0.5), very wide bandwidths (MHz- THz), wavelength-independent size (~cm) and no coupling with the environment. These advantages surpass the capabilities of conventional antenna-based receivers for RF signal detection.
The aim of this thesis is to investigate a hybrid approach to the reception of radio-frequency signals, combining atomic spectroscopy measurement based on Rydberg atoms with the design of a close environment based on metal and/or charged material for shaping and local amplification of the field, whether through the use of resonant or non-resonant structures, or focusing structures.
In this work, the main scientific question is to determine the opportunities and limits of this type of approach, by analytically formulating the field limits that can be imposed on Rydberg atoms, whether in absolute value, frequency or space, for a given structure. The analytical approach will be complemented by EM simulations to design and model the structure associated with the optical atomic spectroscopy bench. Final characterization will be based on measurements in a controlled electromagnetic environment (anechoic chamber).
The results obtained will enable a model-measurement comparison to be made. Analytical modelling and the resulting theoretical limits will give rise to publications on subjects that have not yet been investigated in the state of the art. The structures developed as part of this thesis may be the subject of patents directly exploitable by CEA.
3D ultrasound imaging using orthogonal row and column addressing of the matrix array for ultrasonic NDT
This thesis is part of the activities of the Digital Instrumentation Department (DIN) in Non-Destructive Testing (NDT), and aims to design a new, fast and advanced 3D ultrasound imaging method using matrix arrays. The aim will be to produce three-dimensional ultrasound images of the internal volume of a structure that may contain defects (e.g. cracks), as realistically as possible, with improved performance in terms of data acquisition and 3D image computation time. The proposed method will be based on an approach developed in medical imaging based on Row and Column Addressed (RCA) arrays. The first part will focus on the development of new data acquisition strategies for matrix arrays and associated ultrafast 3D imaging using RCA approach in order to deal with conventional NDT inspection configurations. In the second part, developed methods will be validated on simulated data and evaluated on experimental data acquired with a conventional matrix array of 16x16 elements operating in RCA mode. Finally, a real-time proof of concept will be demonstrated by implementing the new 3D imaging methods in a laboratory acquisition system.
Embedded systems for natural acoustic signals analysis while preserving privacy
The PhD topic aims at developping Embedded systems to record and analyze natural acoustic signals. When targeting city deployement, the privacy issue is raised: how can we keep a satisfactory analysis level while never record or transmit human voices?
SCO&FE ALD materials for FeFET transistors
Ferroelectric Field Effect Transistors FeFET is a valuable high-density memory component suitable for 3D DRAM. FeFET concept combines oxide semiconductors SCO as canal material and ferroelectric metal oxides FE as transistor gate [2, 3]. Atomic layer deposition ALD of SCO and FE materials at ultrathin thickness level (<10 nm) and low temperature (10 cm2.Vs); ultrathin (<5nm) and ultra-conformal (aspect ratio 1:10). The PhD student will beneficiate from the rich technical environment of the 300/200mm CEA-LETI clean-room and the nano-characterization platform (physico-chemical, structural and microscopy analysis, electrical measurements).
The developments will focus on the following items:
1-Comparison of SCO layers (IGZO Indium Gallium Zinc Oxide) fabricated using ALD and PVD techniques: implementation of adapted mesurements techniques and test vehicles
2-Intrinsec and electrical characterization of ALD-SCO (IWO, IGZO, InO) and ALD-EF (HZO) layers: stoichiometry, structure, resistivity, mobility….
3-Co-integration of ALD-SCO and ALD-FE layers for vertical and horizontal 3D FeFET structures
[1]10.35848/1347-4065/ac3d0e
[2]https://doi.org/10.1109/TED.2023.3242633
[3]https://doi.org/10.1021/acs.chemmater.3c02223
Direct metal etch mechanisms study for the BEOL of ultimate SOI nodes
The topic fits into the deployment of silicon technologies at the European level (European chips act), led by CEA-Leti. The focus will be on providing advanced technological building blocks for electrical routing (Back End of Line) of logic and analog devices. The development of increasingly high-performance circuits requires interconnections with more aggressive dimensions. The use of traditional routing materials such as copper is therefore being questioned, as is the conventional back-end of line (BEOL) architecture. This thesis topic will address a breakthrough approach, necessary to achieve these ultimate dimensions.
The objective of this PhD is to develop a BEOL technological building block for the advanced SOI (Silicon on Insulator) nodes through a direct metal etching approach. After a preliminary simulation of the electrical properties of interconnections made with different metals, the work will consist in proposing and implementing an innovative integration. In the first phase, the task will be to determine the design of the electrical test structures and establish an integration scheme. In the second phase, the research work will focus on studying the direct etching of the selected metal using sustainable processes while maintaining the performance of both the processes and the final device. The candidate will be able to rely on the eco-innovation team to perform a comparative life cycle analysis (LCA) of this building block.
The PhD contract is for a duration of 3 years and the research work will take place in the clean rooms of CEA-Leti. To successfully carry out this study, the candidate will have access to state-of-the-art equipment and a cutting-edge work environment.
Laser Fault Injection Physical Modelling in FD-SOI technologies: toward security at standard cells level on FD-SOI 10 nm node
The cybersecurity of our infrastructures is at the very heart in the digital transition on-going, and security must be ensured throughout the entire chain. At the root of trust lies the hardware, integrated circuits providing essential functions for the integrity, confidentiality and availability of processed information.
But hardware is vulnerable to physical attacks, and defence has to be organised. Among these attacks, some are more tightly coupled to the physical characteristics of the silicon technologies. An attack using a pulsed laser in the near infrared is one of them and is the most powerful in terms of accuracy and repeatability. Components must therefore be protected against this threat.
As the FD-SOI is now widely deployed in embedded systems (health, automotive, connectivity, banking, smart industry, identity, etc.) where security is required. FD-SOI technologies have promising security properties as being studied as less sensitive to a laser fault attack. But while the effect of a laser fault attack in traditional bulk technologies is well handled, deeper studies on the sensitivity of FD-SOI technologies has to be done in order to reach a comprehensive model. Indeed, the path to security in hardware comes with the modelling of the vulnerabilities, at the transistor level and extend it up to the standard cells level (inverter, NAND, NOR, Flip-Flop) and SRAM. First a TCAD simulation will be used for a deeper investigation on the effect of a laser pulse on a FD-SOI transistor. A compact model of an FD-SOI transistor under laser pulse will be deduced from this physical modelling phase. This compact model will then be injected into various standard cell designs, for two different objectives: a/ to bring the modelling of the effect of a laser shot to the level of standard cell design (where the analog behaviour of a photocurrent becomes digital) b/ to propose standard cell designs in FD-SOI 10nm technology, intrinsically secure against laser pulse injection. Experimental data (existing and generated by the PhD student) will be used to validate the models at different stages (transistor, standard cells and more complex circuits on ASIC).
Ce sujet de thèse est interdisciplinaire, entre conception microélectronique, simulation TCAD et simulation SPICE, tests de sécurité des systèmes embarqués. Le candidat sera en contact/encadré avec deux équipes de recherche; conception microélectronique , simulation TCAD et sécurité des systèmes embarqués.
Contacts: romain.wacquez@cea.fr, jean-frederic.christmann@cea.fr, sebastien.martinie@cea.fr