Design / Technology Co-Optimization of SRAM and standard cells on stacked nanowires at the 5nm technology node

The post-doctoral position will focus on the layout of SRAM and standard cells dedicated to the 5nm node on stacked nanowires integrating a Direct Self-Assembly solution (DSA). He/she will use the SPICE model developed at LETI and interact with both model and process/integration teams to find the best layout for a set of cells.

Atomic sensors based on metastable 4He

Detection of weak magnetic fields opens the way to new techniques of medical imaging, geophysics and chemistry. Optically pumped magnetometers are currently the most accurate and precise sensors for magnetic fields [1]. Our lab works on optically-pumped magnetometers based on a thermal gas of helium-4 metastables, a spin-one electronic species. Our main achievement in last years has been the design and space qualification of the most recent generation of magnetometers available for spatial exploration, which were launched by ESA Swarm mission [2].
We are now starting a new project in order to explore further applications of magneto-optical effects of metastable helium. Indeed, dichroism and birefringence have been observed on 4He from the very first times of optical pumping [3] but, in strong contrast with alkali [4], the nonlinear regimes which can be reached from the introduction of 1083 nm lasers have been hardly studied. These regimes open new possibilities for realizing not only magnetometers but also other kind of useful sensors which address a broader range of industrial applications.
We are looking for a motivated postdoc candidate willing to work towards a better understanding of these effects but also towards harnessing them for building ultra-precise sensors. The applicant should have a PhD in physics, ideally with a good background in experimental atomic physics and/or laser physics. Our lab is well equipped and staff engineers will be available to assist the post doc on technical aspects related to optics, design of electronics and magnetic materials. The results will be divulgated in form both of journal publications and of patents.
[1] Kominis et al., Nature 422 (2003)
[3] Laloë, Leduc, Minguzzi, Journal de Physique, 30 (1969)
S. Pancharatnam, J. Phys. B: At. Mol. Phys. 1 (1968).
[4] Budker et al., Rev. Mod. Phys. 74 (2002)

New packaging for power electronics : application to SiC components

In continuity of ongoing work (PhD thesis) on the 3D assembly of vertical Silicon power components, the purpose of the post-doc proposal is to develop a similar assembly on vertical wide-gap SiC power components. The required work will be to define the components (high frequency / high voltage) with the supplier and to adapt them to the best vertical integration (Cu finishing, topology,...), to adjust the metal leadframe design for the 3D assembly, and to develop the transfer layer technology adapted to this new material. The candidate will also take care of the electrical characterizations of the final stack to validate the interest of this 3D packaging on wide-gap power devices.

Active medical implants encapsulated using hermetic glass package

Microelectronics extends its range of applications via the micro-systems with high level of integration including sensors, energy scavenger, and communication modules. Medical implants such as pacemakers and defibrillators medical implants, drug dispensers, intra-cranial probes are many possible applications for these modules. The use of glass offers a wide field of investigation. Moreover, recent innovations for the glass material (interconnections, thinning, and functionalization) reinforce its relevance to the medical field: biocompatibility, stability, transparency, and potentially lower cost.
The objective of this work is to design and validate technological steps to integrate high level of microsystems encapsulated in glass material.

Contribution to the development of miniature antennas measuring devices

The generalization of RF links operating at VUHFfrequencies to equip an increasing number of communicating electronic devices helps to intensify research on miniaturization and integration of antennas. As a result, significant progress are regularly carried out to reduce the size of antennas and it is not uncommon to find work describing antenna structures of 1/30 of the wavelength maximum dimension. Increased sensitivity to the operating environment is observable with electrically small antennas. This feature is reflected by problems of measurement of electrical and radiation properties that may be altered with the standard techniques of connecting a measuring cable to the antenna. Accordingly, the subject seeks to develop techniques for electrically small antennas charterization using non-invasive methods, that is to say does not interfere (or few) under test antenna. Two techniques will be investigated based on the work already done in the laboratory. The first technique is based on the far field electromagnetic reflectometry. The second technique involves the use of an RF-optical transducer in the vicinity of the antenna under test for a particular design of miniature optic RF conversion reflectometer for measuring antenna impedance.

Study of cooling solutions for compact electronic systems

3D technologies (i.e. electronic components vertically stacked) constitute an axis of global research, both at the architectural and manufacturing level. The Grenoble area is at the heart of these technological breakthroughs with world first prototypes that make Cea-Leti one of the leaders in these advanced technologies.
One of the critical points of this innovative technology is to control the thermal management in such 3D components regardless of the final application. Nowadays conventional solutions like adding a fan cannot fit all the thermal requirements, and may be of limited effectiveness. More integrated solutions are now unavoidable and can be considered from two points of view: heat can be managed directly at the component-level in silicon chips that make up the 3D-stack, or it can be managed at package level. Ideally, the two approaches should be combined.
The first objective of this study is to achieve an exhaustive state of the art and evaluate the potential of the different solutions for the components developed at Leti. This evaluation will be based on thermal simulations and a critical analysis based on technological feasibility, consumption, efficiency, cost,… and lead to choose the most appropriate solution.
The second part of the work will be dedicated to the implementation of this solution. Relying on experts of silicon and packaging technologies, the candidate will be responsible for contributing to the design of the component (design and implementation) and its characterization.
This position is for a researcher with a strong background in the areas of thermal and microelectronic components. This position requires analysis skills, a large autonomy and unifying skills.

Dual layer transfer of piezoelectric films for advanced RF devices

The aim of these workds is to study and develop an innovating concept of piezoelectric thin films multilayer transfer for RF applications.The applicant will be responsible for the development of the entire fabrication sequence of these multilayer structures and of the 3D RF components. To this end, he or she must master the physical mechanisms involved in the film transfer technology and design the complete architecture through simulation of the expected RF filters properties. Once the structure is defined and the technology backbone is mastered, the candidate will collaborate with Leti technology experts to identify the necessary process developments. He or she will then ensure their implementation in the fabrication technology platform and support the achievement of the most critical steps.
The development of this fabrication sequence will allow the generation of substrates whose features meet device specifications. The functionality of the substrates will then be demonstrated through the fabrication and characterization of RF devices that are relevant to the target applications.

Carbon nanotubes grafting for positive electrodes of lithium/sulfur cells

In a view to develop electric vehicles, researches on lithium batteries are now focusing on sulfur active material. Indeed, this new system should allow to produce cheap and high energy batteries of about 600 Wh/kg. While being developed for more than 40 years, the limitations of such a system are still quite problematic: elemental sulfur is an electronic insulator, sulfur and intermediate lithium polysulfides are soluble in the electrolyte and final discharge product Li2S is non-soluble and insulating too.
This post-doctoral position will thus aim at improving the performances of the sulfur positive electrode, by combining :
- Carbon nanotubes that will allow to improve the electronic conductivity of the positive electrode, as well as to provide a substrate for sulfur grafting
- Disulfide functions that will be grafted on the nanotubes. Thanks to this chemical grafting of active material, the electrochemical reaction would occur without leading to sulfur and polysulfides dissolution, thus leading to higher capacity and cyclability along with lower self-discharge.

Development of a solid electrolyte to optimise lithium microbatteries

All-solid-state microbatteries are developing for nomad applications (RFID, autonomous sensors…). Their main advantages are due to the electrolyte, a thin film inorganic material allowing a very good cyclability (>10000 cycles), long life, good thermal resistivity and excellent safety. These thin film microbatteries have to response to a challenge of integration: decreasing of size but increasing of performances.
The goal of this post-doc is to develop the electrolyte performances. The first part will focus on the optimisation of the actual electrolyte and the second part on the development of a new electrolyte material. The electrolyte deposition will be done by Physical Vapor Deposition.
Le position is in the CEA/LITEN/DTNM/LCMS for a common laboratory CEA/ST Microelectronics.

3D sequential integration

3D integration is currently under great investigation because it offers a solution to keep increasing transistor density while relaxing the constraint on the transistor’s dimension and it eases the co integration of highly heterogeneous technologies compared to a planar scheme.
3D sequential integration offers the possibility of using the third-dimension potential: two stacked layers can be connected at the transistor scale. This contrasts with 3D parallel integration, which is limited to connecting blocks of a few thousand transistors. However, its implementation faces the challenge of being able to process a high performance top transistor at low temperature in order to preserve the bottom FET from any degradation, as the stacked FETs are fabricated sequentially.