Comparison of Diamond and vertical GaN technologies to SiC and Si for power applications
Power devices based on wide band gap semiconductors are increasingly being studied and adopted in commercial products, driven by the electrification of our societies. Among these wide band gap devices, SiC-based technologies are the most mature, at the industrial production stage. Other materials are being studied to achieve higher performance, in particular diamond, whose intrinsic physical properties offer great potential, as well as GaN components in a vertical architecture. However, the real benefits of these materials compared with existing Si or SiC solutions have not been clearly demonstrated and might strongly depend on the applications considered. The aim of this project is to identify one or more applications where vertical GaN and diamond technologies are likely to bring significant benefits, taking into account the current and/or projected market for these applications. Then, using TCAD and SPICE simulations as well as experimental test device characterizations, we will compare the estimated performance of industrially viable diamond and GaN components, designed for these applications, with that of SiC and Si.
High-performance computing using CMOS technology at cryogenic temperature
Advances in materials, transistor architectures, and lithography technologies have enabled exponential growth in the performance and energy efficiency of integrated circuits. New research directions, including operation at cryogenic temperatures, could lead to further progress. Cryogenic electronics, essential for manipulating qubits at very low temperatures, is rapidly developing. Processors operating at 4.2 K using 1.4 zJ per operation have been proposed, based on superconducting electronics. Another approach involves creating very fast sequential processors using specific technologies and low temperatures, reducing energy dissipation but requiring cooling. At low temperatures, the performance of advanced CMOS transistors increases, allowing operation at lower voltages and higher operating frequencies. This could improve the sequential efficiency of computers and simplify the parallelization of software code. However, materials and component architectures need to be rethought to maximize the benefits of low temperatures. The post-doctoral project aims to determine whether cryogenic temperatures offer sufficient performance gains for CMOS or should be viewed as a catalyst for new high-performance computing technologies. The goal is particularly to assess the increase in processing speed with conventional silicon components at low temperatures, integrating measurements and simulations.
Development of optoelectronic systems for quantum sensor technologies
The main mission of CEA LETI's Autonomy and Sensor Integration Laboratory (LAIC) is to develop sensor systems, and in particular quantum sensors for high-precision magnetic field measurement applications. The team's activities are at the interface of hardware (electronics, optronics, semiconductors), software (artificial intelligence, signal processing) and systems (electronic architecture, mechatronics, multiphysics modeling). The Swarm project (https://swarm.cnes.fr/en/), which put our quantum sensors for measuring the Earth's magnetic field into orbit in 2013, is one of our track records, and a new program with similar objectives gets underway this year.
Quantum technologies are strategic for the development of sensors with unrivalled performances, as we have demonstrated in magnetometry. Our challenge today is to adapt these developments and this know-how to new physics.
To support our developments in quantum sensors, we are looking for an opto-electronics post-doc researcher to design new quantum sensors and develop the associated optical benches. This post-doc position will have a significant experimental component.
Your main mission will be to participate to the development of these new sensors and their associated characterization benches, interfacing with CEA experts in the field.
More specifically, your mission will revolve around the following actions:
• Design and assembly of quantum sensors (optical fibers, RF sources, photodetectors)
• Participation in modeling the physical phenomena involved
• Design and build the optical characterization benches
• Development of the control electronics
• Publication of results in scientific journals
• Presentation of work in international conferences
• Patents proposal
Design of 2D Matrix For Silicum Quantum computing with Validation by Simulation
The objective is to design a 2D matrix structure for quantum computing on silicon in order to consider structures of several hundred physical Qubits.
In particular the subject will be focused on:
- The functionality of the structure (Coulomb interaction, RF and quantum)
- Manufacturing constraints (simulation and realistic process constraint)
- The variability of the components (Taking into account the variability parameter and realistic defectivity)
- The constraints induced on the algorithms (error correction code)
- Scalability of the structure to thousands of physical Qubits
The candidate will work within a project of more than fifty people with expertise covering the design, fabrication, characterization and modeling of spin qubits as well as related disciplines (cryoelectronics, quantum algorithms, quantum error correction, …)
Effect of TSV presence on BEOL reliability for 3-layer stacked CMOS image sensor (CIS)
Because conventional downsizing based on the empirical Moore's law has reached its limitations, an alternative integration technology, such as three-dimensional integration (3DI) is becoming the mainstream. The 3rd generation of CMOS image sensor (CIS) stacks up to 3 die interconnected by hybrid bonding and High Density Through Silicon Vias (HD-TSVs). Devices and circuits good functioning and integrity have to be maintained in such an integration especially in the close neighborhood of TSVs. Thermal budget, copper pumping, thin wafer warpage can lead to electrical yield and reliability concerns and must be investigated.
The work consists in evaluating the impact of TSV processing and proximity on BEOL and FEOL performance and reliability. Acquired data sets will help to define design rules and in particular a potential Keep-Out Zone (KOZ) and calibrate a finite element model (FFM).
Design of an embedded vision system integrating a fast intelligent imager
The goal of the postdoc is to evaluate the interest of smart imagers integrating processing in the focal plane in embedded vision systems for a localization function and to propose a complete embedded vision system integrating a smart imager and a host.
The study will focus on ego-localization applications, to realize, for example, a 3D localization function.
From an existing application chain, the post-doctoral fellow will be able to carry out an algorithmic study in order to optimize it to exploit the qualities of the intelligent imager.
Then he will be able to propose a partitioning between smart imager and host system, according to performance criteria.
An experiment using the RETINE smart imager as well as the IRIS host board could be conducted to validate the proposal.
Evaluation of RF system power consumption for joint system-technology optimization
To be able to increase and optimize wireless transmission systems based on a hybridization of technologies, it is strategic to be able to quickly evaluate the capabilities of these technologies and to adapt the associated architecture as best as possible. To this end, it is necessary to implement new approaches to global power management and optimization.
The work of this post-doctoral contract is at this level.
The first step will be to develop some new power consumption models of the RF transceivers building blocks (LNA, Mixer, Filter, PA, …). A modelization approach has already been tested and validated in the group. In the next step, it will be needed to link the performances of the overall wireless system to the building blocks characteristics. Lastly, the optimization will be applied thanks to an efficient solution. Lastly, the proposed approach will be validated in the optimisation of a multi-antenna millimeter wave wireless system. An evaluation methodology specific to 3D will also be put in place
Optomechanical force probes development for high speed AFM
The proposed topic is part of a CARNOT project aiming at developing a new generation of force sensors based on optomechanical transduction. These force sensors will be implemented in ultrafast AFM microscopes for imaging and force spectroscopy. They will allow to address biological and biomedical applications on sub-microsecond or even nanosecond time scales in force spectroscopy mode.
First optomechanical VLSI force probes on silicon have been designed and fabricated in LETI's industrial grade clean rooms and have led to first proofs of concept for fast AFM [1,2]. The post-doctoral student will be in charge of the preparation of force probes in order to integrate them in a high speed AFM developed by our partner at CNRS LAAS (Toulouse). He will be in charge of the back end operations, from the release of the structures, their observation (SEM, optical microscopies, etc.), to the optical packaging with fiber optic ferrules. He will also participate in the development of a test bench for components before and after packaging to select devices and validate the packaged probes before integration into an AFM.
The post-doctoral student will also investigate the operation of the probe in a liquid medium to allow later AFM studies of biological phenomena: for this, the development of efficient actuation means (electrostatic, thermal or optical) of the mechanical structure will be carried out and applied experimentally. A feedback on the modeling and the design is expected from the measurements, in order to ensure the understanding of the observed physical phenomena. Finally, the post-doctoral fellow will have the possibility to propose new device designs to target the expected performances. The devices will be fabricated in Leti's clean room, then tested and compared to the expected performances.
Multi-scale modeling of the electromagnetic quantum dot environment
In the near future, emerging quantum information technologies are expected to lead to global breakthroughs in high performance computing and secure communication. Among semiconductor approaches, silicon-based spin quantum bits (qubits) are promising thanks to their compactness featuring long coherence time, high fidelity and fast qubit rotation [Maurand2016], [Meunier2019]. A main challenge is now to achieve individual qubit control inside qubit arrays.
Qubit array constitutes a compact open system, where each qubit cannot be considered as isolated since it depends on the neighboring qubit placement, their interconnection network and the back-end-line stack. The main goal of this post-doctoral position is to develop various implementation of spin control on 2D qubit array using multi-scale electromagnetic (EM) simulation ranging from nanometric single qubit up to millimetric interconnect network.
The candidate will i) characterize radio-frequency (RF) test structures at cryogenic temperature using state-of-the-art equipment and compare results with dedicated EM simulations, ii) evaluate the efficiency of spin control and allow multi-scale optimization from single to qubit arrays [Niquet2020], iii) integrate RF spin microwave control for 2D qubit array using CEA-LETI silicon technologies.
The candidate need to have a good RF and microelectronic background and experience in EM simulation, and/or design of RF test structures and RF characterization. This work takes place in a dynamic tripartite collaborative project between CEA-LETI, CEA-IRIG and CNRS-Institut Néel (ERC “Qucube”).