Scatterometry measurement of the exposure focal length of photolithography tools
Since the late 2000s with the advent of 45nm CMOS nodes, the control of critical dimensions (CD) of the structures in the photolithography stage has become critical to the reliability of printed circuit boards. Optical photolithography remains the most economical and widespread technique for high volume production in the semiconductor industry. For this type of equipment, manufacturers have focused on increasing the numerical aperture of the exposure lens, reducing sources of optical aberrations and on metrology to ensure efficient monitoring of their machines. These developments were possible at the expense of the depth of field of the exposure. To avoid altering the images transferred to the photosensitive resins, and ultimately have a device failure, it is essential to give a value as accurate and precise as possible of this size. To meet the growing needs of process control and lithography tools required by the most advanced technologies, metrology techniques based on analysis of reflected signals are massively used. Although this methodology is well suited to current CMOS technologies (CMOS14nm and earlier), it is unlikely to address more advanced technologies, so other techniques must emerge, such as techniques based on the analysis of the diffracted signal (scatterometry).
Study of NMC electrode materials for lithium-ion batteries by experimental and theoretical soft and hard X-ray photoemission spectroscopy
The photoemission spectroscopy (X-ray, XPS, or ultraviolet, UPS) is one of the direct probes of the electronic structure of materials change during redox processes involved in lithium ions-batteries at the atomic scale. However, it is limited by the extreme surface sensitivity, with a typical photoelectron path length of a few nanometers to the energies usually available in the laboratory , . Moreover, the spectra interpretation requires the ability to accurately model the electronic structure, which is particularly delicate in the case of transition metal based electrode materials. Upon lithium insertion and de-insertion, the charge transfer toward cations and anions induces local electronic structure changes requiring an adapted model that takes in account the electronic correlations between atoms.
In this thesis, we propose to use these limitations to our advantage to explore the electronic surface structure including the solid electrolyte interphase (SEI), and the bulk of the active cathode particle.
Thanks to the lab-based hard X-ray photoemission spectrometer (HAXPES), the electronic structure of the bulk of the electrodes (LiCoO2 and LiNiO2) materials have been studied up to about 30 nanometers , . To widen our picture on the role of cation and anion from surface to bulk in the lamellar metal oxide electrode for lithium-ion battery, this thesis will focus on mixed lamellar metal oxide Li(Ni1-x-yMnxCoy)O2 (NMC).
The comparison between the Soft-XPS and HAXPES spectra, during battery operation (operando) and post-mortem, will allow decoupling of the surface and core spectra for different NMC compositions and at different stages of the battery life cycle. The interpretation of the photoemission spectra will be done by direct comparison with ab-initio calculations combining density functional theory (DFT) with dynamical mean field theory (DMFT) , . This coupled approach will allow to go beyond the usual techniques based on cluster models, which do not take into account long-range screening, and to validate the quality of theoretical predictions on the effects of electronic correlations (effective mass, potential transfer of spectral weight to Hubbard bands) .
The thesis will include an instrumental (in particular, calibration of Scofield factor on model systems) and theoretical (prediction of core photoemission spectra based on DFT+DMFT calculations) development. The performance of electrochemical systems based on different cathode materials (NMC with different compositions) in combination with liquid and solid electrolytes and a Li metal anode will be studied in the frame of combined experimental and theoretical soft and hard X-ray photoemission spectroscopy.
The candidate will be hosted at the PFNC in the Laboratory of Characterization for the Energy of CEA Grenoble under the direction of Dr. Anass BENAYAD (department of Material) and LMP (Department of Electricity and Hydrogen for Transport) under the supervision of Dr. Ambroise Van Roekeghem.
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MEMS chaotic motion for high sensitivity
Improving the resolution of MEMS sensors always means increasing the cost of the component (surface area) or his electronics (complexity and power consumption). In view of the current challenges of energy sobriety, it is essential to explore new disruptive ways to reduce the impact of high-performance sensors.
Chaos is a deterministic phenomenon exponentially sensitive to small variations. Little studied until recently, it can be simply implemented in the dynamics of MEMS sensors, to amplify weak signals and increase resolution.
Ultimately, this is an "in-sensor computing" method, making it possible to do away with some of the measurement electronics.
The aim of this thesis is to create the first MEMS demonstrator for in-sensor computing in the chaotic regime. To achieve this, we propose to study, through in-depth characterization/modeling work, this new operating regime on MEMS sensors already available at DCOS/LICA (M&NEMS and MUT beams). These first steps in understanding the link between measurand and MEMS response in the chaotic regime will enable us to move on to other applications, notably in the field of cryptography.
Electrical characteization and Reliability of NextGeN FDSOI MOSFETs
Global demand on semiconductor solutions (device, circuit, system) has skyrocketed during the last few years, especially in reliation with COVID worldwide crisis. This industry has revealed its significance in the present world has well as its weaknesses. The European council decided to launch an ambisious program called 'Chip Act' to develop a solid semiconductor european industries network based on its champions such as ST microelectronics, SOITEC and the CEA-LETI. In France, the french government decided to push forward the FDSOI technology using the CEA-LETI to develop the 10nm node and beyond.
The reach the MOSFET expected performance of such an aggressive node, several original technological solutions are considered, such as the use of Si-channel stressors to boost the mobility and the ON state current or the use of thinned Si channel film and gate oxide. The influence of these novel processes and technological bricks on MOSFET FoM and reliability must be carefully studied before entering in a production mode. The PhD student will address the electrical characterization of the High-k/Metal Gate stacks (initial performance) and their long term reliability (aging under stress). Electrical modeling of the experimental data will be used to determine the crucial parameters to improve and give quick feedback to the Device development Lab.
Characterization of the grafting efficiency of antigenic proteins to capsid like particles for vaccine development
Among the vectors used to develop vaccines, virus-like particles (VLPs) are particularly interesting for the transfer of antigens (Ag). In fact, VLPs self-assemble into molecular motifs associated with pathogens, triggering vigorous immune responses, thus avoiding the need for adjuvants. As part of an ANR project in partnership with the Institut de Biologie Cellulaire Intégrative de Gif sur Yvette and the Institut Gustave Roussy de Villejuif, we are interested in the structural characterization of vaccines based on T5 bacteriophage pseudocapsids (T5-CLP).
During development, various quality indicators need to be reliably assessed to guide vaccine design, control production or verify safety and stability. Several attributes affecting the purity, efficacy and safety of T5-CLPs have been identified. Among these, the amount of Ag grafted is considered critical, as it determines vaccine efficacy. In this thesis, we propose to develop the potential of nanocharacterization technologies to rapidly and reliably validate the antigenic load of these vaccine particles. To do this, we will draw on conventional approaches such as proteomics and electron microscopy, and on a selection of advanced nanocharacterization technologies including nanoresonator mass spectrometry.