Line edge roughness extraction with a sub-nanometer resolution

Within the European Chips Act, CEA-Leti is strongly committed to support the reduction of component dimensions to reach the future technological nodes (below 10 nm). To detect and account the line edge roughness becomes critical for such small dimensions since ‘the few Angstrom error’ becomes critical (several % of error) for sub-10nm devices.
This PhD work will focus mainly on the use of CD-SAXS to define the sensibility of the technique. To do so, we propose to follow two main complementary directions: first to perform simulations with tools under developments to identify the exact impact of roughness on a CD-SAXS pattern; and secondly to lead the experimental measurements on samples specifically designed at the CEA-LETI with controlled roughness. . CD-SAXS measurements will be done both on the laboratory equipment at the CEA as well as at synchrotrons (ESRF, NSLS-II). These results will be compared with results obtained from CEA-LETI cleanroom metrology equipment, such as AFM-3D and CD-SEM.
This PhD will take place between the Nanocharacterization platform of the CEA–LETI witch offer world-class analytical techniques and state-of-the-art instruments and the cleanroom metrology team from the CEA-LETI.

Quantification of strategic binary compounds by hard X-ray photoemission (HAXPES) and combined surface analysis

The main objective of the thesis is to provide reliable support to the processing of front-end materials for advanced FD-SOI technologies. To achieve this, methodologies for elemental quantification focused on the use of hard X-ray photoelectron spectroscopy (HAXPES) will be developed and validated through a collaborative framework at multiple levels, both internal and industrial.
These collaborations will enable to pool upstream work aimed at a better understanding of quantification in HAXPES at all levels (intensity measurement, types of sensitivity factors used, measurement reproducibility).
In a second step, the protocols will be applied to the targeted technological materials and then optimized. The targeted materials are primarily silicon and germanium compounds contributing to the optimization of the channels of advanced FD-SOI transistors, such as Si:P, SiGe, and their derivatives (GeSn, SiGe:B). A combined analytical approach involving other nanoscale characterization techniques will be strengthened by identifying the most appropriate techniques to produce reference data (ToF-SIMS, RBS, etc.).
In a third step, multi-scale aspects will be developed. In particular, they will aim to investigate to what extent the composition measured by HAXPES on a material developed upstream of transistor integration steps (for process deposition optimization) compares to that determined by other techniques (atom probe tomography, TEM-EDX, TEM-EELS) at the end of nanometric device integration.

Impact and cohabitation of Lithium on a microelectronics platform

Context: Lithium-based materials, whether thin layers or bulk material, are of great interest for varied applications (batteries, RF components…). However, their cohabitation with other “standard” materials for microelectronics requires special attention regarding dissemination in the clean room and a potential impact on electrical performances of devices. Indeed, as a precaution, these materials are “confined” on dedicated manufacturing lines, without full knowledge of their potential effect on the manufactured devices. This work aims at understanding the phenomena leading to lithium dissemination, to propose solutions to keep it under control and to take advantage of possible beneficial effects.
Mission: During this Ph.D. thesis, you will work in close collaboration with a multidisciplinary team in CEA and with their partners. This will involve highlighting the possible vectors of Lithium dissemination in common manufacturing spaces in clean rooms. Furthermore, you will define a methodology to identify and quantify Lithium in various materials and at their interfaces using physicochemical characterization tools available to the “Ion Beams” and “Operational Metal Contamination” (clean room) teams from the Surfaces & Interfaces Analysis Laboratory (LASI). A large part of the work will rely on ion beam analysis technics such as secondary ion mass spectrometry. This implementation will allow studying the mechanisms and kinetics of lithium diffusion as well as to evaluate its impact on the performance of “microelectronics” devices.
Profil: Chemist, physicist, engineer, etc., you have knowledge in chemistry/physics on materials/ semiconductors. Holder of a Bac+5, you are curious, rigorous, creative and wish to participate in a 3-year research project in support of microelectronics.

Performance and Reliability Evaluation of Ferroelectric Memories Based on Hafnium Oxide for Integration into Advanced Nodes.

An explosion in global data production is observed today, largely attributed to the emergence of 5G and the Internet of Things. Faced with the challenges of managing vast amounts of data and to avoid a significant increase in global electricity consumption due to data storage, it is necessary to develop efficient, energy-efficient, and dense non-volatile memory technologies.

The discovery of ferroelectricity in hafnium oxide (HfO2) in 2010 has sparked notable interest both in the scientific and industrial domains for ferroelectric memories. These devices offer significant advantages, including reduced energy consumption, good scalability to advanced technological nodes, high endurance, and fast read/write speeds.

This thesis aims to assess the electrical performance and reliability of non-volatile ferroelectric memory components based on HfO2 manufactured at CEA-Leti. The overall objective is to integrate these memories into advanced technological nodes to increase density while reducing energy consumption and operating voltages. Understanding the physical mechanisms responsible for the degradation of ferroelectric material properties will be crucial. To achieve this, various types of memory components ranging from single cells to matrices of several tens/hundreds of kilobits will be available for conducting this work. A portion of the thesis will also involve identifying obstacles to the integration of these materials into advanced technological nodes.

3D chemical investigation of 10 nm FDSOI CMOS devices.

The development of 10 nm FDSOI (Fully Depleted Silicon On Insulator) technology leads to new constraints on the architecture of transistors. The gate width (10 nm) requires a specific integration of the gate that controls the threshold voltage. The variability of the threshold voltage depends on the concentration, spatial distribution and chemical nature of dopants in the source and drain area. Therefore, it is crucial to understand the impact of growth conditions of the metallic gate, source, drain and annealing temperature to activate the dopant. To master these new constraints, the use of characterization techniques that can identify the structural and chemical mechanisms (distribution and quantification) acting in the gate, source and drain will be essential. Among all the chemical characterization techniques, Atom Probe Tomography is the technique of choice that offers a 3D chemical and quantitative mapping of a sample with nanometre scale resolution.
The objectives of this PHD will be to: (i) develop 3D characterization methodologies (distribution and chemical composition of species within the gate and source-drain area) of transistors, (ii): investigate the impact of growth conditions, annealing temperature activating the dopants and implantation dose. The PHD student will try to model the formation mechanisms of the observed chemical compounds.

Enabling patterning fidelity analysis over millimetric distances for curvilinear mask data-preparation : application to photonics devices.

Integrated silicon photonics, which consists of using manufacturing processes from the microelectronics industry to produce photonic components, is considered a critical future technology for very high-speed communications and computing applications.
The creation of silicon photonics devices requires the manipulation of fully curved designs (so-called non-Manhattan). This gives rise to numerous challenges during their manufacturing, and particularly during the design stage of advanced photolithography masks. In order to determine the optimal masks, optical effects compensation (OPC) algorithms are systematically applied. The latter are particularly difficult to implement in the particular case of curvilinear patterns.
The accuracy with which OPC models are able to anticipate pattern printing performance can be assessed using CD-SEM on specific, simple, small structures in a single orientation. However, Photonic devices (for example, waveguides) are continuous, up to a few millimeters long, and cover all orientations in space. A broad and precise metrology of such objects does not exist, making it impossible for OPC engineers to diagnose the quality of the devices produced on the product.
The objective of the thesis is to develop a method for precise, large-scale dimensional measurement of Photonic structures. In particular, we will seek to implement solutions for stitching SEM images and extracting contours, with the development of dedicated metrics. The thesis proposes in particular:
- the study of metrological and scripted solutions to enable characterization by CD-SEM on a large scale, typically by combining several images.

- the implementation of extraction of contours of curved patterns on recombined images.

- the development and implementation of innovative 2D metrics to allow the measurement of curved objects, then their comparison with each other (or with a reference).

- the inclusion of real large-scale contours in optical simulation software (Lumerical, FDTD) to characterize the real performance of the devices.

The thesis will take place for 3 years between the STMicroelectronics site (Crolles) and that of CEA-LETI (Grenoble), in a context of strong collaboration between the teams of the two organizations.

The doctoral student will have access to clean rooms and state-of-the-art industrial and/or research equipment, as well as commercial reference software. You will benefit from all the technical expertise of the supervisory teams at STMicroelectronics and CEA-LETI in photolithography, metrology, image processing and applied IT development (Python).
?

Understanding Dopant Incorporation Mechanisms in Heavily-Doped Semiconductors using combinations of high resolution (S)TEM techniques

Context: There is a need for very highly-doped semiconductor specimens for the continued development of Si/Ge CMOS devices and for doping III-V materials where the ionisation energy leads to a low concentration of carriers. In order to provide these highly doped specimens, new growth and implantion methods are required. These need to be better understood and characterised with nm-scale resolution.
Proposed Subject: We will combine various (scanning) transmission electron microscope (S)TEM techniques, such as electron holography, precession electron diffraction, spectroscopy and high-resolution imaging on the same specimen. Advanced data processing techniques will be developed in order to combine the different maps to provide information about the total dopant concentration, the quantity of dopants on substitutional sites, and the active dopant concentrations. This work will provide methodology to assess the effectiveness of the different processes that are used for doping in advanced CMOS research. This includes FD-SOI 10 nm and below, raised and embedded source and drains, Si:P, SiGe:B, Low Temperature / Coolcube.

Multiscale overlay measurements

In the microelectronics industry, the lithography step is monitored using image-based overlay (IBO) or diffraction-based overlay (DBO) measurement techniques. These techniques are relatively simple to implement, fast and their specifications meet the needs of mature technologies (CMOS20nm and earlier). To exploit these techniques, dedicated metrology structures need to be integrated into specific areas. These structures have a specific design that differs from the product being manufactured. This raises the question of the representativeness of the overlay measurement resulting from these metrology techniques compared with the overlay in the product. New methods such as scanning electron techniques (SEM) are currently being developed, the major advantage of which is their ability to measure at any point in the product and in a repeatable manner. However, this technique deteriorates certain materials. Further studies must therefore be carried out to find the best conditions for using this technique in order to establish the link between misalignment in the product and comparison with measurements using conventional techniques (IBO and DBO). Other techniques, such as X-ray techniques or other methodologies will be investigated (defect analysis method, machine learning, etc.). This work will enable us to address more effectively the new technological nodes currently being developed at LETI.

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.
Contact : anass.benayad@cea.fr et ambroise.vanroekeghem@cea.fr

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.

Top