We are looking for highly motivated candidates to work on our projects
PhD and Post-doc positions below
contact : nick.barrett@cea.fr
Post-doctoral positions
Multi-level functionality in ferroelectric, hafnia-based thin films for low-power, edge logic and memory
To cope with the requirements of Artificial intelligence at the edge, new architectures have to be explored in the light of new emerging devices technologies. In the context of the Horizon Europe Ferro4EdgeAI collaborative project, we aims to develop and demonstrate from 1000X to 2500X energy efficiency gain with respect to cloud based CMOS for intelligent edge processors based on ferroelectric technology and the computation-in-memory paradigm.
The unique characteristics of FE technology [Silva2023] will be explored in the light of the targeted applications. The device technology at the heart of Ferro4EdgeAI is the FeFET-2 in which a ferroelectric capacitor is added in series with the gate stack of a conventional CMOS transistor (Figure). Conceptually this combines the simplicity and endurance/retention characteristics of the FeRAM with the plasticity and quasi-analogue response of the FeFET, without the adverse effects of charge trapping on endurance, retention, imprint and drift.
The primary objective of the materials aspect of Ferro4EdgeAI is the optimization of HfO2-based ferroelectric materials for multilevel functionality suitable for AI applications by investigating the trade-off in memory window, film thickness & stability of the ferroelectric state. We require a FE film which offers the possibility for a large memory window (large remanent polarization), able to retain the set polarization states.
The post-doctoral research will focus on the switching kinetics of films with different process parameters and switching voltages will be analysed via time-resolved X-ray photoemission spectroscopy (XPS, PEEM) with a time-resolved detector funded by the project to characterize ML switching.
(left) I-V characteristic of a simple FeFET showing the quasi-analog response as a function of gate voltage [Mulaosmanovic2018]. (right) FeFET-2 with BEoL FE capacitor in series with the MIS gate stack.
CAD image of retractable 2D-DLD (white element) after the double hemispherical analyzer and the PEEM projective lens. Objective lens optics and sample manipulator in yellow (FOCUS GmbH).
Extensive use of synchrotron radiation is foreseen for the operando experiments. Samples will be supplied by NaMLab (Dresden) and the CEA LETI (Grenoble) who will also provide the integration.
In addition to the scientific research, the successful candidate will be expected to assist in project management and interact with all of the consortium partners, in particular for reporting and organization of regular project meetings.
The initial contract is for 22 months, June 2024 start date, negotiable
CV and contact details for two references before 31st March 2024 to Nick Barrett (nick.barrett@cea.fr)
[Silva2023] J.P.B. Silva et al, Roadmap on ferroelectric hafnia-and zirconia-based materials and devices APL Mater. 11, 089201 (2023)
[Vianello2019] Vianello, E., L. Perniola, and B. De Salvo. Emerging memory technologies for neuromorphic hardware Advances in Non-Volatile Memory and Storage Technology. Woodhead Publishing 585 (2019)
[Mulaosmanovic2018] H. Mulaosmanovic et al., Accumulative Polarization Reversal in Nanoscale Ferroelectric Transistors ACS Appl. Mater. Interfaces 10, 23997 (2018)
Dopant and Defect Physics for Device Optimization for Hafnium Oxide based Devices (Position Filled)
Dopage et physique des défauts pour l'optimisation des propriétés électriques de l’oxyde d’hafnium ferroélectrique
Devices realized with ferroelectric hafnium oxide are silicon compatible, power-efficient, and can be cost-effectively integrated into advanced technology nodes for sensor, nonvolatile memory, logic, and neuromorphic applications. Currently, hafnium-zirconium mixed oxide (HfxZr1-xO2) offers the widest stoichiometry window for fabricating ultrathin ferroelectric films with large remanent polarization. Still, the film requires oxygen vacancies to stabilize the ferroelectric phase and has reliability issues. An alternative could be to start from stoichiometric, quasi-vacancy-free hafnia and use suitable dopants to optimize the ferroelectric properties.
We will explore the influence of the dopant modulated atomic and electronic structure on the ferroelectric properties. The chosen materials will be optimized by successive simulation, processing, and characterization iterations and integrated into scaled arrays to provide statistically significant results on ferroelectric capacitor performance.
The post-doctoral research will give a better understanding of the influence of dopants on local chemistry, electronic structure, phase composition, and their effects on material and ferroelectric parameters, including recrystallization temperature and remanent polarization. The work will be done by employing a range of static and operando experiments on bare films and electrode/film interfaces (HAXPES, XPS, PFM, PEEM, XRD) in both laboratory and synchrotron environments. Operando experiments will correlate device endurance with material physical properties and electrical characterization will be carried out.
The results will be compared with ab initio calculations and will provide input for physical models based on real devices to predict key metrics such as wake-up, endurance, retention, leakage, and breakdown using vacancy-free doped hafnia.
The D3PO project is a Franco-German collaboration between the CEA, NaMLAb (Dresden) and the Technische Hochschule München, jointly funded by the ANR and the DFG.
Candidates should have a PhD in physics with good background in oxide materials, ferroelectrics or photoemission spectroscopy.
The initial contract is for 24 months
Autumn 2023 start date is preferred
CV and contact details for two references before 30th September 2023 to
Nicholas BARRETT
DRF/IRAMIS/SPEC
Bâtiment 462
CEA Saclay
91191 Gif sur Yvette
France
nick.barrett@cea.fr
High throughput heterostructures characterization for hafnia-based microelectronics (Position Filled)
Ferroelectricity in HfO2 thin films (10nm) was unveiled 12 years ago,[1] changing the paradigm of ferroelectric memories due to CMOS compatibility and scalability of hafnia. Even though a significant amount of work has been published during the last decade, the optimization of the ferroelectric properties remains complex because of the metastable nature of orthorhombic phase. Improving device performance therefore requires the simultaneous optimisation of both the individual layers (thickness, stoichiometry, crystallinity…) and their metastructure i.e. the optimization of the stack as a whole. We will develop a combinatorial analysis providing lateral resolution on the scale of the expected chemical and physical variations and depth resolution on the scale of the implemented heterostructures. The advanced characterization methods employed will use Photoemission electron microscopy (PEEM) in laboratory environment and Hard X-ray Photoelectron spectroscopy (HAXPES) with synchrotron radiation. The aim of the project is to validate a complete artificial intelligence assisted, high throughput synthesis / characterization chain leading to accelerated production of optimized microelectronic devices and generation of material database resources.
Within the framework of the Diadem MicroElec project, funded by the Agence Nationale de la Recherche (ANR), two advanced characterization platforms will be implemented here. PEEM in laboratory environment will use a high intensity focused X-ray source adapted for imaging of multiple ferroelectric capacitors (FeCAPs). Dedicated sample-holders will allowing wiring of multiple FeCAPs for operando HAXPES analysis with synchrotron radiation. The combinatorial analysis of the resulting datasets will probe materials with the required range of Dx and Dz and provide full physical chemical screening of operational prototypical structures. Samples will be elaborated in close collaboration with the CEA/Léti (Grenoble). Experiments will be carried out in CEA Saclay and in synchrotron radiation centres, notably Soleil synchrotron.
Candidates should have a PhD in physics with good background in oxide materials, ferroelectrics or photoemission spectroscopy.
The initial contract is for 12 months, renewable 12 months. Autumn 2023 start date is preferred.
CV and contact details for two references before 30th April 2023 to
Nicholas BARRETT
DRF/IRAMIS/SPEC
Bâtiment 462
CEA Saclay
91191 Gif sur Yvette
France