Study and evaluation of a micro resonator based thermal sensor for uncooled infrared imagery
The project aims at establishing the feasibility of a novel infrared microbolometer sensor exploiting the thermal sensitivity of a free oscillating micro-nano-mechanical system (M & NEMS), whose resonant frequency changes with the infrared flux it absorbs. This is a concept out who was the subject of three patents.
The project addresses the needs of high resolution uncooled infrared imaging sensors (spectral band ranging from 8µm to 12µm) which is presently in expansion but whose next generation of products is still waiting for a breakthrough to reduce the pixel size, a key factor to improve performance and reduce the cost.
The objective of this post doctoral study is to achieve a proof of concept of this new architecture. In this outlook, the study will cover first the sizing of the device, then its design, implementation and validation at a single pixel level.
Distributed multiagent resources allocation. Application to district heating
Heating district networks in France fed more than one million homes and deliver a quantity of heat equal to about 5% of the heat consumed by the residential and tertiary sector. Therefore, they represent a significant potential for the massive introduction of renewable and recovery energy. However, heating networks are complex systems that must manage large numbers of consumers and producers of energy, and that are distributed in extended and highly branched geographical zones. The aim of the SIGMA project, realized in collaboration among the CEA-LIST and the CEA-LITEN, is to implement an optimal and dynamic management of heating networks. We propose a multidisciplinary approach, by integrating the advanced network management using Multi-Agent Systems (MAS), by taking into account spatial constraints using Geographic Information Systems (GIS) and by considering simplified physical models of transport and recovery of heat.
The post-doc’s goal is to design mechanisms for dynamically allocating resources that consider the geographical information from the GIS and the predictions of consumption, production and losses calculated with the physical models. In this way, several characteristics of the network will be considered: the continuous and dynamic aspect of the resource; sources with different behaviors, capabilities and production costs; the dependence of consumption / production to external aspects (weather, energy price); the internal characteristics of the network (losses, storage capacity). The coupling with a GIS should allow implementing self-configuration mechanisms for the management of different networks and different levels of granularity obtained by reduction of the original GIS. The MAS should dynamically establish the link between the suitable simplified models and the desired level of granularity and then it will create the agents needed to represent the system.
Development of innovative metal contacts for 2D-material field-effect-transistors
Further scaling of Si-based devices below 10nm gate length is becoming challenging due to the control of thin channel thickness. For gate length smaller than 10nm, sub-5nm thick Si channel is required. However, the process-induced Si consumption and the reduction of carrier mobility in ultrathin Si layer can limit the channel thickness scaling. Today, the main contenders that allow the extension of the roadmap to ultra-scaled devices are 2D materials, particularly the semiconducting transition metal dichalcogenides (TMD). Due to their unique atomically layered structure, they offer improved immunity to short-channel-effects in comparison to usual Si-based field-effect-transistors (FETs). This makes them very attractive for the application of more-Moore electronics.
However, the scalability of MOSFET device and the introduction of new material make source and drain contact a major issue. If many efforts have been made, in the past years, to reduce Fermi level pinning and Schottky barrier height, for many, these approaches are not industrially scalable. The main objective of this work is then to propose an in-depth understanding of electrical contact characteristics (based on different material) to identify the lowest contact resistance. The processes involved, offering an optimal contact resistance, must be compatible with wafer-scale processing for an integration in our 200/300mm advanced CMOS platform. The post-doc will in-depth study mechanisms enabling the formation of small contact resistances (between MoS2 and metal). It will have to identify the most promising contact material and to develop the associated deposition processes (ALD/PVD). Finally, electrical characterization of contact will be performed to qualify both material and interfaces enabling optimal operation of future 2D FETs
Selective removal of metal alloy for advanced silicidation applied to sub-20nm CMOS transistors
CMOS transistor performances depend on electrical contact resistivity reduction. Thus, self aligned silicidation (salicide) is one of the key processes which have to be improved to meet the ITRS requirements for the future technological nodes. Nowadays, solid state reaction between thin metal layer (Ni1-yPty < 10nm) and a silicon substrate allows to decrease access resistances of transistor source & drain. The metal is currently deposited by physical vapor deposition method all over the wafer surface. Under heat treatment, metal reacts preferably with semiconductor areas rather than dielectrics ones. Then, unreacted metal layer is selectively etched with an appropriate acidic solution; only metal silicide remains.As new specifications (use of ultra-thin Ni-alloy,very low temperature process leading to partial salicidation, use of various additive metals ...)are required for advanced nodes (C20nm & C14nm), the capability to chemically remove the excess of metal on dielectric areas has to be investigated. In the clean room environment of CEA-LETI (Grenoble, France), the candidate will work on innovative wet chemistries to remove selectively the different metallic layers (Ni, Pd, NiCo, NiPd…). In a first time preliminary test will be conducted on sample in manual tank in order to check removal kinetic and global selectivity on structures devices… Based on several characterization techniques (TXRF, XRR, AFM, SEM, TEM, XRD…), residual additive interaction with dielectric and chemical mixture behavior towards the metal rich phase on silicided area (roughness, resistivity) will be studied. Different semi-conductor (Si, SiGe…) and dielectrics surfaces (SiO2, SixNy…) will be investigated. Afterwards the most promising selective processes will be selected to be installed on a fully automatic 300mm tool. Finally, best processes will be integrated on critical patterned wafer architectures for morphological and electrical characterizations.
Design of integrated photonics modules
Design of next generation optoelectronic transceivers (particularly on-board modules) requires the merging of two advanced technologies: Silicon Photonics and 3D Silicon Packaging, both being developed at Leti.
In order to meet the requirements in term of technical specifications, cost and density, it is needed to achieve a codesign involving mechanical, thermal, optical and mainly RF aspects.
The aim of the work consists in designing such integrated modules by optimizing the RF interconnections of the module (internal and external), and the proper setup of the integrated circuits (ASICs). Modelling of several architectures will be led under HFSS and ADS softwares.
Finally, the integration of the module into its system environnement will be taken in charge, so as its characterization (involving testboard and testbench design).
Real time low cost algorithms for brain computer interface with multiple degrees of freedom
The topic of the postdoctoral project is the optimization of BCI methods and algorithms for medical application in humans (quadriplegic subjects).
Namely the particular goal of the postdoctoral fellow will be optimization and the acceleration of calculation to allow multiple degrees of freedom (up to 26) in real time. Selecting the appropriate features subset will improve the computational efficiency and the quality of control. To this purpose the algorithms of sparse modeling will be applied.
To map ECoG recordings to the spatial-temporal-frequency space, continuous wavelet transform (CWT) is applied. Optimization will include the implementation of low cost CWT and C++ coding.
The project will include the test and the adaptation of BCI algorithms to wireless signal transmission with the implant WIMAGINE.
Finally the adaptation of algorithms to medical environment of quadriplegic subjects (the use of imaginary tasks, presence of stimuli in the signal, the restricted duration of experiments) will be under responsibility of postdoctoral scientist.
Development of a Metal Supported Cell for Hydrogen production by High Temperature Steam Electrolysis
The development of Metal Supported Cells (MSC) for High Temperature Steam Electrolysis (HTSE) constitutes an interesting innovation able to reduce the degradation of this component under operation. An increase in the cell life time would be a valuable contribution to cost reduction and is able at positioning HTSE as an alternative process to other hydrogen production technologies. However, some progresses in the elaboration of MSCs are still required. Within the current process, functional ceramic layers of the MSC are joined to the metallic substrate at elevated temperature (> 1000 °C). Mismatch of the mechanical properties of the materials as well as the reducing conditions fixed by the metal substrate during sintering lead to MSCs having insufficient electrochemical performances. The post-doctorate aims, on the one hand, at obtaining a better understanding of the mechanisms that occur in the multilayer structure during sintering and, on the other hand, at proposing and testing technological solutions able to improve to reliability of MSC elaboration.
Reverse engineering of an internal permanent magnet synchronous electrical machine and modelisation of evolutions based on new new magnet technologies developped in CEA
The study aims at studying and modeling a synchronous electric motor with magnet buried in the rotor. This study begins with a preliminary phase of retro engineering and modeling of an existing machine. A second phase will focus on the design and the modeling of a new machine integrating a new technology of magnets developed in the CEA.
In the context of electric transportation, if batteries and energy storage are still the weak point of the energy chain, the electric motor remains a central part that has to be optimized to raise efficiency. For twenty years, all motor structures have been studied and tested: dc motors, synchronous machines with permanent magnets, asynchronous machines and switched reluctance machines. This study will focus on a synchronous machine with magnets buried into the rotor. This type of machine offers a natural ability of delivering at full load a constant power along a wide speed range, associated with a high efficiency. Moreover, power density can be improved by increasing maximal speed range.
The Post doc will be split into three parts:
1st phase:
Testing of an existing commercial electrical synchronous machine with magnets buried in the rotor and characterization of its components. These tests will be done on a motor test bench situated in the CEA
2nd phase:
Modeling of the commercial machine tested on the test bench and comparison of modeling results with experimental measurements from the first phase.
3rd phase:
Design and modeling of evolution of the machine tested and modeled in phases 1 and 2, integrating new technologies of magnets developped by the CEA.
Reliability of the copper (Cu) direct bonding interconnects for 3D integration
Copper direct bonding is one of the most promising approaches for 3-D integration. The process is mature as shown in the literrature for wafer to wafer (W2W) approach [1-3] but also in the case of a die to wafer one (D2W). However, its reliability is yet to be demonstrated even if the initial results from the PhD thesis of R. Taibi seem to be promising [4].
The purpose of this post-doc position will be first, to consolidate the results obtained by R. Taibi with the W2W approach and secondly, to study the reliability of the D2W approach from the electromigration and stress-induced voiding point of view.
The candidate will be responsible for all the reliability study, starting with the tests and the results’ analysis, failure analysis (optical, IR, SEM, FIB...), the determination of the degradation’s mechanisms.
1. Gueguen, P., et al. Copper direct bonding for 3D integration. in Interconnect Technology Conference, 2008. IITC 2008. International. 2008.
2. Taibi, R., et al. Full characterization of Cu/Cu direct bonding for 3D integration. in Electronic Components and Technology Conference (ECTC), 2010 Proceedings 60th. 2010.
3. Di Cioccio, L., et al., An Overview of Patterned Metal/Dielectric Surface Bonding: Mechanism, Alignment and Characterization. Journal of The Electrochemical Society, 2011. 158(6): p. 81-86.
4. Taibi, R., et al., Investigation of Stress Induced Voiding and Electromigration Phenomena on Direct Copper Bonding Interconnects for 3D Integration, in 2011 IEEE International Electron Devices Meeting (IEDM). 2011: Washington, DC.
Electrical Study of Conductive Bridge Random access Memory (CBRAM)
CBRAM memories are among the most promising technologies as alternative to Flash technologies which face strong problems of scaling. CBRAM have a capacitor-like stack, where a chalcogenide material is sandwiched between a silver anode and an inert cathode. Biasing the cell, silver ions diffuse in the chalcogenide matrix and reach the cathode where they reduce. A conductive bridge is formed between the electrodes causing a drop of resistance. Reversing the bias yields to a back-migration of silver, interrupting the conductive bridge. This kind of device can be operated at very low voltage (below 1 V) and can lead to extremely low power consumption.
The main objective of this postdoc position will be the electrical characterization aiming to a better comprehension of the physics involved in the device, with the final goal of a strong improvement in device characteristics, in particular concerning data retention. For this aim, in-depth characterization on particular features (i.e. conduction mode, failure mechanisms) will be performed, as much as possible linked to a first level of physical modelling linking current conduction and diffused ions in the matrix. The candidate will address both hardware & methodology issues, and particular attention will be devoted to pulsed measurements. Various process, geometries and architectures will be studied. A strong interaction with the specialists of materials characterizations (nano-characterization platform) will be promoted for a better physical knowledge of the structures.