Papers by Jean-herve Tortai
IEEE Transactions on Semiconductor Manufacturing
Spectroscopic ellipsometry is a very sensitive optical metrology technique commonly used in semic... more Spectroscopic ellipsometry is a very sensitive optical metrology technique commonly used in semiconductor manufacturing lines to accurately measure the thickness and refractive index of different layers present on specific dedicated metrology targets on the wafers. In parallel, optical defectivity techniques are widely implemented in production lines to inspect a significant amount of dies representative of the full wafer and detect physical and patterning defects. A new approach can then simply emerge which is to apply ellipsometry metrology techniques at a full or die wafer scale. This strategy, at the frontier between metrology and defectivity field is expected to bring solutions for certain types of process deviation. In our case, ellipsometry's optical response was collected on large areas of product wafers to capture specific deviations such as film properties, thickness, and patterning variation. This is an innovative strategy that relies on a model-less approach to detect process drifts, using ellipsometry's sensitivity to material properties and design architecture variations. In this paper, we will present this approach on three industrial cases.
Materials Chemistry and Physics
In this study, we first compare the bandgap determination methods in SiON thin films using two es... more In this study, we first compare the bandgap determination methods in SiON thin films using two established techniques: Ellipsometry and the Energy Loss Spectrum from X-ray Photoelectron Spectroscopy. In the ellipsometry case, we modelled the optical properties using a single Tauc-Lorentz oscillator model, in a range from 1.5 to 6 eV, while for the XPS case, we used the threshold energy of the Energy Loss Spectrum from the O1s and N1s main core levels to determine the bandgap. We observed a consistent difference of the energy bandgap values obtained between the two methods, reaching up to 1.6 eV. Therefore, we combined the ellipsometry and Energy Loss Spectrum from XPS measurements, creating a hybrid metrology method using a triple Tauc-Lorentz oscillator model. This methodology respected the optical relations of each technique and the complex dielectric constant of the material, creating an overlap of the two measurements between 3.5 and 6 eV. The combination method brings the advantage of a more robust determination of the bandgap in the SiO2-Si3N4 system, while creating a way to measure the refractive index and coefficient of extinction for intermixed thin films of SiON, from 1.5 up to 30 eV.
2022 33rd Annual SEMI Advanced Semiconductor Manufacturing Conference (ASMC)
Full wafer measurement techniques are used in the semiconductor industry to acquire information a... more Full wafer measurement techniques are used in the semiconductor industry to acquire information at a large scale to control process variation or detect potential defects. This process usually results in the generation of full wafer images, containing various objects that need to be identified to evaluate their impact on the final product performance. Artificial intelligence is very powerful to automate this identification routine. In this paper, we present the application of Region-based Convolutional Neural Networks (RCNN) for enhanced process control from full wafer images gathered by two industrial metrology equipments.
2020 31st Annual SEMI Advanced Semiconductor Manufacturing Conference (ASMC), 2020
Spectroscopic ellipsometry is a very sensitive metrology technique to accurately measure the thic... more Spectroscopic ellipsometry is a very sensitive metrology technique to accurately measure the thickness and the refractive index of the different layers present on specific dedicated metrology targets. In parallel, optical defectivity techniques are widely implemented in production lines to inspect a large number of dies and catch physical and patterning defects during the process flow. It becomes then of interest to explore a new approach overlapping metrology and defectivity by using the sensitivity of metrology tools on a full wafer scale. In our case, spectroscopic ellipsometry's optical response was collected directly on the dies to capture specific deviations such as film properties and thickness variation. This is an innovative strategy that requires a model-less approach, combining an automatic ellipsometry mapping generation and a smart classification via a machine learning algorithm. In this paper, we will present such approach on two industrial use cases and explain how an image classification algorithm can be implemented to automatically detect the process drift on the latter.
SEM metrology is widely used in microelectronics to control patterns dimensions after many proces... more SEM metrology is widely used in microelectronics to control patterns dimensions after many processes, especially patterning. Process control is achieved by verifying that experimental dimensions match targeted ones. However SEM metrology may give erroneous measurements if strong charging occurs. Charging effect impacts on the SEM image contrast and introduces artefacts. This article intends to report on the modeling of the physical phenomena occurring when the electron gun scans a sample and how charging effect occurs. For this, charge dynamics are modeled by taking into account the drift kinetics and the diffusion of electrons. The corresponding Partial Differential Equation system is solved using FEniCS open software. First, we show that when only top view measurement are modeled, the typical contrast of SEM pictures can not be predicted. Second, cross section views are modeled. This time, the expected contrast behavior is obtained. Finally, a full 3D simulation is presented.
Nowadays, the accuracy of the metrology is becoming more and more a critical issue for microelect... more Nowadays, the accuracy of the metrology is becoming more and more a critical issue for microelectronic manufacturing as new technology nodes necessitate more and more rigorous process control. Scanning Electron Microscope (SEM) is the equipment most typically used to measure pattern dimensions. The aim of this study is to model and simulate a synthetic SEM image. This is fulfilled by taking into account the physical phenomena that take place in the sample during the scanning of the electron beam. The considered phenomena are the kinetics of the drift and the diffusion of the charges during the scanning and the secondary electrons emission from the sample into the vacuum. A system of Partial Differential Equations (PDEs) is obtained which defines a system that will be solved using the Finite Element Method. The escaping of the secondary electrons is modeled by applying a Robin boundary condition on the top surface of the sample. By computing the secondary electron emission that origi...
Microscopy and Microanalysis, 2021
Composites Science and Technology, 2021
High-k nanocomposite photoresists are highly sought-after dielectric materials for the manufactur... more High-k nanocomposite photoresists are highly sought-after dielectric materials for the manufacturing and miniaturization of integrated capacitors. Herein, in-depth high voltage dielectric characterizations of Metal Polymer Composites (MPCs) having carbon-coated nickel nanoparticles (Ni@C) dispersed into epoxy-based photoresist (SU-8) are reported. The MPCs were fabricated using three-step formulation (deagglomeration, surface functionalization and dispersion in a polymeric matrix) involving simple sonochemical methods. Finally, films of MPCs were deposited on silicon wafers by spin-coating, and Metal-Insulator-Semiconductor (MIS) capacitors were fabricated. Formulations with increasing nanoparticles/polymer volume fractions were prepared in order to determine a previously unestablished percolation threshold with (Ni@C) nanoparticles. The experimental results were modeled using the generalized power-law equation of the percolation theory (PT) and were compared with effective medium approximation (EMA). An enhancement of the complex dielectric permittivity of 116% was detected keeping a reasonable value of losses of 0.32 at 5 kHz. However, no giant permittivity in vicinity of the percolation threshold was detected. The high-voltage dielectric properties showed the occurrence of two electron field emission mechanisms, but no electrical aging or dielectric breakdown below ±0.38 MV/cm occurred. This study shows a reliable wafer-scale film fabrication process of MPCs for the manufacturing of long-awaited miniaturization of high-voltage capacitors.
The Journal of Physical Chemistry C, 2019
CMOS-compatible, refractory conductors are emerging as the materials that will advance novel conc... more CMOS-compatible, refractory conductors are emerging as the materials that will advance novel concepts into real, practical plasmonic technologies. From the available pallet of materials, those with negative real permittivity at very short wavelengths are extremely rare; importantly they are vulnerable to oxidation-upon exposure to far UV radiation-and nonrefractory. Epitaxial, substoichiometric, cubic MoN (B1-MoNx) films exhibit resistivity as low as 250 cm and negative real permittivity for experimental wavelengths as short as 155 nm, accompanied with unparalleled chemical and thermal stability, are reported herein. Finite-difference time domain calculations suggest that B1-MoNx operates as an active plasmonic element deeper in the UV (100-200 nm) than any other known material, apart from Al, while being by far more stable and abundant than any other UV plasmonic conductor. Unexpectedly, the unique optical performance of B1-MoNx is promoted by nitrogen vacancies, thus changing the common perception on the role of defects in plasmonic materials.
SpringerPlus, 2016
Background Polymer nanocomposites are attractive materials due to the ability to tailor final pro... more Background Polymer nanocomposites are attractive materials due to the ability to tailor final properties. They consist in nanometer fillers embedded in a matrix. The properties are controlled by the filler volume fraction. Composites are classified into diluted or densely packed states (Leslie-Pelecky and Rieke 1996). With metallic fillers, the continuum percolation theory applies to the electrical conductivity (Hunt and Ewing 2009). Also dipolar-magnetism in interacting systems was reported (Varón et al. 2013). In RF, polymer-metal nanocomposites are aimed to overcome the main obstacle of high-moment transition metals that are conductive. Recent works on nanocomposites of cobalt were reported but magnetization degradation was observed indicating that stable nanoparticles are needed (Nelo et al. 2010; Raj et al. 2014). They can be protected with a shell that must be a protection against surface oxidation and spin-quenching especially with cobalt (van Leeuwen et al. 1994). The shell thickness must be small as with
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Journal of Vacuum Science & Technology B, Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phenomena, 2015
Proximity effects in electron beam lithography impact feature dimensions and uniformity. These ef... more Proximity effects in electron beam lithography impact feature dimensions and uniformity. These effects are addressed using a mathematical model representing the radial exposure intensity distribution produced by a point source of electrons, commonly named point spread function (PSF). Unfortunately, the multiple Gaussian distribution approximation, the most common PSF model used till now, reaches its limits in terms of efficiency, particularly in case of high atomic number Z substrate materials. A broad family of approximating functions, known as splines, is considered here as a substitute to Gaussian. Through a simulation study using specific test structures, the authors demonstrate the high potential of cubic splines in accurately characterizing high Z substrates PSFs.
SPIE Proceedings, 2013
ABSTRACT Proximity Effects in electron beam lithography impact feature dimensions, pattern fideli... more ABSTRACT Proximity Effects in electron beam lithography impact feature dimensions, pattern fidelity and uniformity. These effects are addressed using a mathematical model representing the radial exposure intensity distribution induced by a point electron source, commonly named as the Point Spread Function (PSF). PSF models are usually employed for predicting and compensating for effects up to 15μm. It is well known that there are also some process related phenomena that impact pattern uniformity that have a longer range, namely CMP effects, fogging, etc. Performing proximity effects corrections can result in lengthy run times as file size and pattern densities continue to increase exponentially per technology node. Running corrections for extreme long range phenomena becomes computational and file size prohibitive. Nevertheless, since extreme long range may reach up several millimeters, and new technology nodes require a high level of precision, a strategy for predicting and compensating these phenomena is crucial. In this paper a set of test patterns are presented in order to verify and calibrate the so called extreme long range effects in the electron beam lithography. Moreover, a strategy to compensate for extreme long range effects based on the pattern density is presented. Since the evaluation is based on a density map instead of the actual patterns, the computational effort is feasible. The proposed method may be performed off-line (in contrast to machine standard in-line correction). The advantage of employing off-line compensation relies on enhancing the employ of dose and/or geometry modulation. This strategy also has the advantage of being completely decoupled from other e-beam writer’s internal corrections (like Fogging Effect Correction - FEC).
Metrology, Inspection, and Process Control for Microlithography XXIII, 2009
In this paper, an ill-posed inverse ellipsometric problem for thin film characterization is studi... more In this paper, an ill-posed inverse ellipsometric problem for thin film characterization is studied. The aim is to determine the thickness, the refractive index and the coefficient of extinction of homogeneous films deposited on a substrate without assuming any a priori knowledge of the dispersion law. Different methods are implemented for the benchmark. The first method considers the spectroscopic ellipsometer as an addition of single wavelength ellipsometers coupled only via the film thickness. The second is an improvement of the first one and uses Tikhonov regularization in order to smooth out the parameter curve. Cross-validation technique is used to determine the best regularization coefficient. The third method consists in a library searching. The aim is to choose the best combination of parameters inside a precomputed library. In order to be more accurate, we also used multi-angle and multi-thickness measurements combined with the Tikhonov regularization method. This complementary approach is also part of the benchmark. The same polymer resist material is used as the thin film under test, with two different thicknesses and three angles of measurement. The paper discloses the results obtained with these different methods and provides elements for the choice of the most efficient strategy.
Microelectronic Engineering, 2013
Proximity effects in electron beam lithography impact feature dimensions, pattern fidelity and un... more Proximity effects in electron beam lithography impact feature dimensions, pattern fidelity and uniformity. These effects are addressed using a mathematical model representing the effect of the electron exposure and the subsequent effect of the resist. Therefore, one of the key steps of any proximity effect correction procedure is to determine properly the parameters of the model. However, the approach of extracting the parameters of a model based on measurements requires that the patterns measured are sensitive enough to the characteristics of the process that are described by the model. In this work it is presented a sensitivity analysis technique that allows the evaluation of the capability of a given test pattern to provide information over every parameter of a proposed model. Finally, a test pattern is presented in order to validate this approach. The proposed pattern is evaluated by the sensitivity analysis techniques described on this paper and then a calibration procedure is executed based on simulation results (with and without noise). Results shows accurate model calibration when the pattern set presents sensitivity to all its parameters.
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Papers by Jean-herve Tortai