Une des voies actuelles d'amelioration des composants de puissance est l'integration de structures de protection (Robb et al., 1994; Seki et al., 1994). Nous avons precedemment etudie une structure de protection des IGBT contre les courts-circuits. Cette structure a ete etudiee en detail et optimisee en vue de sa realisation dans un process conventionnel d'IGBT (Caramel et al., 2006). L'integration de structures de protections sur le meme substrat que le composant de puissance a proteger souleve le probleme d'isolation entre les parties haute et basse tension. Nous verrons que dans notre application, l'isolation des composants basse tension entre eux est aussi necessaire. Pour palier a ce probleme, nous proposons trois techniques d'isolation compatibles avec un process d'IGBT classique. Nous avons realise des simulations 2D pour mettre en exergue la necessite d'isolation et pour comparer l'efficacite des differentes techniques d'isolation.
In this work, the correlation between BEMA model and FTIR analysis was employed to investigate the chemical composition of silicon oxynitride (SiOxNy) films deposited by low pressure chemical vapour deposition (LPCVD) technique at temperature of 850 °C from nitrous oxide N2O, ammonia NH3 and dichlorosilane SiH2Cl2. Different stoichiometries were obtained for different values of relative gas flow ratio NH3/N2O while keeping the SiH2Cl2 flow constant. The optical properties were studied using spectroscopic ellipsometry. Apart from films thickness, their refractive index as well as their SiO2 and Si3N4 volume fractions were deduced using the Bruggeman effective medium approximation (BEMA) model. It was found that the refractive index increases from 1.45 to 1.60 with increasing nitrogen incorporation. The Fourier Transform Infrared spectroscopy was carried out to study the evolution of chemical bonding of LPCVD SiOxNy films. In order to improve the qualitative analysis of their Si-N and Si-O vibrational modes, a correlation between Fourier transform infrared and spectroscopic ellipsometry measurements was established. A shift of infrared peaks position with the increase of relative gas flow ratio is observed. Furthermore, the calculated areas of absorption bands were used to estimate the SiOxNy stoichiometry. This quantitative analysis was proved with an adequate method in the literature. We found a decrease of x values from 1.94 to 1.26 and an increase of y from 0.04 to 0.49, when the NH3/N2O gas flow ratio increases. This behavior was explained by the increase of nitrogen content as well as the decrease of oxygen content in the SiOxNy film.
The huge increase of datacom capacities requires lasers sources with more and more bandwidth performances. Vertical-Cavity Surface-Emitting Lasers (VCSEL) in direct modulation is a good candidate, already widely used for short communication links such as in datacenters. Recently several different approaches have been proposed to further extend the direct modulation bandwidth of these devices, by improving the VCSEL structure, or by combining the VCSEL with another high speed element such as lateral slow light modulator or transistor/laser based structure (TVCSEL). We propose to increase the modulation bandwidth by vertically integrating a continuous-wave VCSEL with a high-speed electro-modulator. This vertical structure implies multiple electrodes with sufficiently good electrical separation between the different input electrical signals. This high frequency modulation requires both good electrical insulation between metal electrodes and an optimized design of the coplanar lines. BenzoCyclobutene (BCB) thanks to its low dielectric constant, low losses, low moisture absorption and good thermal stability, is often used as insulating layer. Also, BCB planarization offers the advantages of simpler and more reliable technological process flow in such integrated VCSEL/modulator structures with important reliefs. As described by Burdeaux et al. a degree of planarization (DOP) of about 95% can be achieved by simple spin coating whatever the device thickness. In most of the cases, the BCB planarization process requires an additional photolithography step in order to open an access to the mesa surface, thus involving a tight mask alignment and resulting in a degraded planarization. In this paper, we propose a self-aligned process with improved BCB planarization by combining a hot isostatic pressing derived from nanoimprint techniques with a dry plasma etching step.
The dynamic simulation of a sub-scale ITER Central Solenoid (CS)/STRucture (STR) cooling loop has been performed to investigate the cryogenic control strategies against pulsating heat loads. HELIOS facility has been modified for this particular study, which consists of a Liquid Helium (LHe) reservoir with two immersed heat exchangers, a circulation pump and an approximately 130 m long piping with three evenly distributed heated sections. The setup provides the equivalent thermo-hydraulic configuration of the ITER CS/STR, cooled by the forced-flow Supercritical Helium (SHe). The dynamic simulator, C-PREST, has been utilized to model the HELIOS test loop and to compare the results with the experimental data sets. This paper presents the dynamic simulation results and discusses the control strategy to minimize the cooling power requirements, to have high reliability.
This work concerns the use of the thermal step method (TSM) for measuring electric charge in metal-oxyde-semiconductor (MOS) structures used in micro and nano-electronics. The TSM is a non destructive method for quantifying and localizing the electric charge in solid insulating materials and structures. Its principle is the application of a low thermal step to a short-circuited or dc-biased sample and the analysis of a current response, which depends on the charge present in the device. An adaptation of the technique (so far used in thick insulating materials and structures for electrical engineering) to short-circuited and biased MOS devices, is described. Results obtained on biased MOS structures and their correlation with classical capacitance-voltage (C-V) measurements are given. Estimations, by the TSM, of the amount of charge trapped in the oxide and of the space charge penetration depth in the silicon substrate are presented.
In this paper, a new monolithic integrated device providing the "thyristor dual" function without auxiliary supply and based on the functional integration mode is investigated. The influence of the physical and technological parameters of this new structure upon the main electrical characteristics and the physical behaviour has been analyzed using the ATLAS software tool. An optimized device is proposed and test structures have been fabricated.
