GaN Technologies: From The Improvement Of Device Reliability To The Design Of Robust High Frequency Circuits

International audienc

Non-destructive techniques for evaluating the reliability of high frequency active devices

International audienceSiGe and GaN technologies have achieved rapid development over the last two decades. High level of RF circuit integration on Si low cost substrates open the way for large development of SiGe HBTs, while needs for high power density make GaN HEMT a key technology for solid state power modules. As both of these technologies achieve very elevated frequencies, they become strong contenders to GaAs technologies. Then reliability studies are needed to improve the process at the lower technology readiness level scale, and to stabilize the technological process till the final qualification step. To make an efficient diagnostic on the causal origin of the physical root mechanisms involved during the application of a stress, a multi-tool approach is mandatory to secure the diagnostic. In this paper, case studies on SiGe HBT and GaN HEMT stressed devices are proposed through the cross-analysis of low frequency noise spectral densities, of electrical transient measurements, and of TCAD simulations

LE BRUIT DE FOND ÉLECTRIQUE DANS LES COMPOSANTS ACTIFS, CIRCUITS ET SYSTÈMES DES HAUTES FRÉQUENCES : DES CAUSES VERS LES EFFETS

Les travaux présentés dans ce mémoire d'habilitation portent sur l'impact du bruit de fond électrique sur les technologies des composants actifs, les circuits et les systèmes des hautes fréquences. Durant nos 12 dernières années de recherche, nous nous sommes notamment intéressés à des filières émergentes à fort potentiel d'intégration (BiCMOS Silicium-Germanium) ou encore à forte puissance (GaN) : nous avons ainsi développé des modèles électriques (petit signal et fort signal) et en bruit (basse fréquence et haute fréquence) des composants actifs pour identifier les pistes d'améliorations technologiques, pour localiser les défauts structurels ou pour étudier le comportement de ces mêmes défauts après l'application de contraintes simulant un vieillissement accéléré. Sur la base de la connaissance des composants actifs (transistor bipolaire à hétérojonction et transistors à effet de champ), nous avons développé des circuits intégrés MMIC faible bruit à 10 GHz et 20 GHz (amplificateurs et oscillateurs) dont certains se positionnent à l'état de l'art : des comparaisons de topologies ont notamment été réalisées sur différentes versions intégrées d'oscillateurs contrôlés en tension de type MMIC SiGe. Nous proposons également une discussion sur la pertinence des facteurs de mérite usuellement employés. D'autres études sur des atténuateurs programmables MMIC SiGe ont fait l'objet de brevets. La troisième partie, orientée système, aborde l'étude du bruit d'un récepteur : nous traitons ainsi le cas d'un étage de réception affecté par la chaîne d'émission, en proposant différentes parades permettant de limiter les dégradations de son plancher de bruit ; une technique de filtre compact intégré à l'amplificateur faible bruit a ainsi été brevetée. Enfin, le cas d'un système de liaison hertzienne embarqué sur automobile est abordé. Diverses stratégies sont ainsi proposées pour pallier les évènements conduisant à une rupture de la liaison (diversité temporelle, diversité spatiale et diversité de polarisation). Ces études reposent sur une approche mixte de traitement de mesures par des modèles théoriques, et des simulations électromagnétiques

Diagnostic Tools For Accurate Reliability Investigations of GaN Devices

International audienceIntensive development of GaN-based HEMT devices has been largely pushed by their intrinsic capabilities for operation at high temperature under high voltage conditions, making the difference with the competitive technologies. However, a poor electrical reliability under high-electric-field operation is still hampering large-scale penetration of these technologies into the RF power market. From the early 2000, an increased number of works have addressed reliability issues. The first ones have been conducted on the basis of roadmaps issued from reliability investigations previously carried out on III-V and silicon based devices. These investigations have enlightened that several parameters such as surface passivation, processing techniques alternatives and piezoelectric effects severely impact device reliability. In order to get a deeper understanding of the correlation between physical and electrical events, we simultaneously report low frequency noise (LFN) measurements data (including separation of the different noise sources involved), and electrical measurements data (lag effects on drain and gate terminals, I-DLTS measurements, ...) conducted on the same devices. The later investigations are appropriate in order to identify defects that are able to produce noise. Noise measurements versus temperature on virgin and stressed devices are reported for different GaN processes developed by a French industrial foundry. Lorentzian noise shapes are identified and activation energies are extracted from Arrhenius plots. Additionally, I-DLTS measurements are performed. Electric lag measurements on the gate and drain terminals are finally used in order to relate stress impact to the electrical integrity of the devices. The identification of failure mechanisms needs accurate statements, and the effectiveness of such a melting of different kind of experiments is demonstrated

LE BRUIT DE FOND ÉLECTRIQUE DANS LES COMPOSANTS ACTIFS, CIRCUITS ET SYSTÈMES DES HAUTES FRÉQUENCES : DES CAUSES VERS LES EFFETS

Les travaux présentés dans ce mémoire d'habilitation portent sur l'impact du bruit de fond électrique sur les technologies des composants actifs, les circuits et les systèmes des hautes fréquences. Durant nos 12 dernières années de recherche, nous nous sommes notamment intéressés à des filières émergentes à fort potentiel d'intégration (BiCMOS Silicium-Germanium) ou encore à forte puissance (GaN) : nous avons ainsi développé des modèles électriques (petit signal et fort signal) et en bruit (basse fréquence et haute fréquence) des composants actifs pour identifier les pistes d'améliorations technologiques, pour localiser les défauts structurels ou pour étudier le comportement de ces mêmes défauts après l'application de contraintes simulant un vieillissement accéléré. Sur la base de la connaissance des composants actifs (transistor bipolaire à hétérojonction et transistors à effet de champ), nous avons développé des circuits intégrés MMIC faible bruit à 10 GHz et 20 GHz (amplificateurs et oscillateurs) dont certains se positionnent à l'état de l'art : des comparaisons de topologies ont notamment été réalisées sur différentes versions intégrées d'oscillateurs contrôlés en tension de type MMIC SiGe. Nous proposons également une discussion sur la pertinence des facteurs de mérite usuellement employés. D'autres études sur des atténuateurs programmables MMIC SiGe ont fait l'objet de brevets. La troisième partie, orientée système, aborde l'étude du bruit d'un récepteur : nous traitons ainsi le cas d'un étage de réception affecté par la chaîne d'émission, en proposant différentes parades permettant de limiter les dégradations de son plancher de bruit ; une technique de filtre compact intégré à l'amplificateur faible bruit a ainsi été brevetée. Enfin, le cas d'un système de liaison hertzienne embarqué sur automobile est abordé. Diverses stratégies sont ainsi proposées pour pallier les évènements conduisant à une rupture de la liaison (diversité temporelle, diversité spatiale et diversité de polarisation). Ces études reposent sur une approche mixte de traitement de mesures par des modèles théoriques, et des simulations électromagnétiques

Evolution Trends and Paradigms of Low Noise Frequency Synthesis and Signal Conversion Using Silicon Technologies

Silicon technologies for HF applications have been proven for more than two decades, and technologies have greatly evolved. Whether CMOS or BiCMOS technologies, the unique combination of radio frequency, baseband, and digital functions allow a very high level of integration. While it is possible to achieve fully integrated transceivers, the major advantages of these silicon technologies lie mainly in their unparalleled performance in the field of frequency synthesis and frequency conversion. We propose in this paper a review of the major results obtained on these RF components since the beginning of the 2000s, also considering the impact of the technology node. The back-end of line (BEOL) process on which depends the quality of microwave monolithic integrated circuits (MMICs) is briefly presented in the introductory part. If circuit performances are tightly bound to the active devices (i.e., the heterojunction bipolar transistor SiGe HBT or CMOS transistor), passive elements (i.e., quality factor of inductors and varactors, losses of transmission, or interconnection lines) as well as the definition of the substrate also play a major role. The core of the article is oriented toward the noise of synthesized signals and frequency conversion. Frequency synthesis is presented through the analog design of a voltage-controlled oscillator (VCO) or through the direct digital frequency synthesis (DDFS), for which respective figures of merit are presented and discussed in a second section. The spectral purity of the oscillators being decisive in the definition of the throughput of a link is approached through the comparison of different figures of merit (FoM) for a set of circuits achievements over the selected period. If the realization of free oscillators is closely bound to the phase-locked loop (PLL)-type control loop for VCOs, the DDFS solution provides more direct and more flexible alternative at first sight. Therefore, these two solutions are analyzed collectively. Finally, the oscillator integrated in the transmitter or receiver supplies the needed LO (local oscillator) power to the frequency mixer in the frequency conversion module: henceforth, the third part of this study focuses on high-frequency mixer realizations. We thus consider this LO power in some advanced figure of merit mentioned in the second section. The design trade-off of the mixer is presented in an approach combining LO (conversion gain, channel isolation, and phase noise) and RF (HF noise figure and channel isolation) constraints. The final section provides a summary of the results and trends mentioned in the paper

LA TECHNOLOGIE GAN ET SES APPLICATIONS POUR L'ELECTRONIQUE ROBUSTE, HAUTE FREQUENCE ET DE PUISSANCE

publié dans la revue "L'actualité Composants du CNES, N°27, 1er trimestre 2008", Centre Competence Technique, CNESveille technologique sur la filière GaNDepuis le début des années 90, une nouvelle catégorie de filières dites à large bande interdite est venue compléter l'éventail déjà large des technologies utilisées pour les capteurs, pour l'optique, pour l'électronique de puissance et pour l'électronique des hautes fréquences. Les technologies carbure de silicium (SiC) et nitrure de gallium (GaN) possèdent des qualités intrinsèques remarquables, et représentent ainsi une véritable rupture technologique avec les technologies GaAs et Si/SiGe. Leur développement offre de nouvelles opportunités en terme de conception de circuits, voire d'architecture de systèmes (réseau de transpondeurs des applications radar, gestion de l'énergie des systèmes embarqués, ...) en panachant les différentes technologies disponibles pour des applications en optique, en opto-électronique et en électronique. Ce papier propose un état de la technologie GaN et de ses applications HF : les principaux acteurs mondiaux sont présentés, ainsi que les performances des technologies, quelques démonstrateurs de circuits HF et premiers résultats sur la fiabilité de ces filières

Low-Frequency Noise Measurements and Applications: Low-Frequency Noise Metrology For The Development of High-Frequency Technologies and For High Purity Signal Generation

International audienceThis presentation concerns the metrology and applications of low frequency noise in the field of very high frequency electronics. Noise metrology has its own constraints, and its own mathematical relationships to translate the fine mechanisms that define the electronic detection thresholds. The presentation will take place in two parts: one dedicated to the metrology of LF noise (LFN) measurements and the other related to their applications.The optimization and definition of an experimental device for the LFN depend on its specifications, which itself depends on the targeted limits to be measured or the ease of use for the targeted buyer. The definition of the measurement setup (and their associated equations), the compromises of settings (gain, bandwidth, RF-DC decoupling and current and impedance levels) are given by the presentation of different setups. A comparison of the advantages, drawbacks and limitations is given between home-made and commercial setups. User-friendly ease of use and detection noise floor are primarily defined by the trade-off between the ability to drive the DC signal generator or to bias the DUT from batteries. Many performances that define the quality of the LFN measurement arise from these RF-DC decoupling considerations.The second part of the presentation focuses on the applications of these LF noise measurements; it distinguishes the design of RF circuits from the study of noise sources and their evolution during the application of stresses (DC, Thermal, RF) for reliability studies.The design of high purity oscillators (MIC and MMIC) is a major concern for telecom, radar or radiometer applications. This presentation provides some intuitive design guidelines for BiCMOS (VCO MMIC) and GaN (fixed oscillator MIC and VCO) technologies. Phase noise is defined as the distance between the electrical power of the carrier (signal) and the noise at a given frequency of the carrier. SiGe technology is the best choice when it comes to LF noise and its NL conversion of phase noise, but GaN technologies offer an increased carrier signal by one to two decades and can also be considered despite higher LF spectra.The last part of the presentation concerns the use of LFN measurement to locate defects within an active device (HBT, HEMT). It also presents the use of noise spectroscopy to study the dependence of a defect versus the application of a stress (evolution of the spectra and specific monitoring of the electrical signature of the noise). The LFN represents a powerful tool to develop reliability studies, since it represents a non-invasive measurement (however, we need to DC bias the device and likely to perform measurements at different temperatures for the Arrhenius plots!). Chosen case of study are given as illustrative purpose on both SiGe HBT technologies and GaN HEMT technologies

Low-Frequency Noise Measurements and Applications: Low-Frequency Noise Metrology For The Development of High-Frequency Technologies and For High Purity Signal Generation

International audienceThis presentation concerns the metrology and applications of low frequency noise in the field of very high frequency electronics. Noise metrology has its own constraints, and its own mathematical relationships to translate the fine mechanisms that define the electronic detection thresholds. The presentation will take place in two parts: one dedicated to the metrology of LF noise (LFN) measurements and the other related to their applications.The optimization and definition of an experimental device for the LFN depend on its specifications, which itself depends on the targeted limits to be measured or the ease of use for the targeted buyer. The definition of the measurement setup (and their associated equations), the compromises of settings (gain, bandwidth, RF-DC decoupling and current and impedance levels) are given by the presentation of different setups. A comparison of the advantages, drawbacks and limitations is given between home-made and commercial setups. User-friendly ease of use and detection noise floor are primarily defined by the trade-off between the ability to drive the DC signal generator or to bias the DUT from batteries. Many performances that define the quality of the LFN measurement arise from these RF-DC decoupling considerations.The second part of the presentation focuses on the applications of these LF noise measurements; it distinguishes the design of RF circuits from the study of noise sources and their evolution during the application of stresses (DC, Thermal, RF) for reliability studies.The design of high purity oscillators (MIC and MMIC) is a major concern for telecom, radar or radiometer applications. This presentation provides some intuitive design guidelines for BiCMOS (VCO MMIC) and GaN (fixed oscillator MIC and VCO) technologies. Phase noise is defined as the distance between the electrical power of the carrier (signal) and the noise at a given frequency of the carrier. SiGe technology is the best choice when it comes to LF noise and its NL conversion of phase noise, but GaN technologies offer an increased carrier signal by one to two decades and can also be considered despite higher LF spectra.The last part of the presentation concerns the use of LFN measurement to locate defects within an active device (HBT, HEMT). It also presents the use of noise spectroscopy to study the dependence of a defect versus the application of a stress (evolution of the spectra and specific monitoring of the electrical signature of the noise). The LFN represents a powerful tool to develop reliability studies, since it represents a non-invasive measurement (however, we need to DC bias the device and likely to perform measurements at different temperatures for the Arrhenius plots!). Chosen case of study are given as illustrative purpose on both SiGe HBT technologies and GaN HEMT technologies

X-band and K-band low-phase-noise VCOs using SiGe BiCMOS technology

International audienceFrom the past two decades, SiGe transistors have been identified as excellent candidates to match requirements both for high purity signal generation and high frequency applications. Moreover, SiGe BiCMOS technology benefits from CMOS devices that allow high integration levels for monolithic microwave integrated circuit (MMIC) phase locked loop (PLL) systems. This work focuses on the only analogue circuit of a PLL: the voltage controlled oscillator (VCO) which is one of the cornerstones of a transceiver because its stability mainly influences the data rate of the channel. X-band and K-band VCOs are investigated. Design rules are compared for two different topologies in the X-band. The K-band VCO is also designed to assess the technology behaviour for higher frequencies. State-of-the-art results are obtained and compared with the best published performances to date. New expressions of a figure of merit (FOM) are proposed to provide an accurate comparison between designs featuring scattered performances