Дисертації з теми "Diode à avalanche à photon unique"

La photod??tection est un sujet de recherche tr??s actif encore de nos jours et l???industrie, particuli??rement de la physique des hautes ??nergies et de l???imagerie m??dicale, est en qu??te de d??tecteurs avec une plus grande sensibilit??, de meilleures r??solutions temporelles et une plus grande densit?? d???int??gration. Pour ces raisons, les photodiodes avalanche ?? photon unique (Single photon avalanche diode, ou SPAD) suscitent beaucoup d???int??r??t depuis quelques ann??es pour ses performances en temps et sa grande photosensibilit??. Les SPAD sont des photodiodes avalanche op??r??es au-dessus de la tension de claquage et un photoporteur atteignant la r??gion de multiplication peut ?? lui seul d??clencher une avalanche soutenue de porteurs et entra??ner le claquage de la jonction. Un circuit d??tecte le courant divergent et l?????touffe en abaissant la polarisation de la jonction sous la tension de claquage. Le circuit recharge ensuite la jonction en r??appliquant la tension initiale permettant la d??tection d???un nouveau photon. Dans le but d???augmenter le nombre de photons simultan??s d??tectables, les SPAD s???int??grent en matrice. Cependant, dans le cas o?? une matrice de SPAD et leurs circuits d?????touffement s???int??grent sur le m??me substrat, la surface photosensible devient limit??e par l???espace qu???occupent les circuits d?????touffement. Dans le but d???augmenter leur r??gion photosensible, les matrices de SPAD peuvent s???int??grer en trois dimensions (3D) avec leurs circuits d?????touffement. Ce projet porte sur le d??veloppement de matrices de SPAD en technologie CMOS HV 0,8 ??m de Teledyne DALSA d??di??es ?? une int??gration 3D avec leurs circuits d?????touffement actifs. Les r??sultats de caract??risation montrent que les SPAD atteignent une r??solution temporelle de 27 ps largeur ?? mi hauteur (LMH), poss??dent un taux de comptage en obscurit?? (DCR, ou Dark Count Rate) de 3 s[indice sup??rieur -1]??m[indice sup??rieur -2] et ont une probabilit?? de photod??tection (PDP) de 49 %. De plus, une m??thode d???isolation utilisant un puits p a ??t?? d??velopp??e. Les SPAD con??us avec cette m??thode ont un facteur de remplissage pouvant atteindre 54 % et une probabilit?? de diaphonie de 6,6 % ?? une tension exc??dentaire ?? la tension de claquage (V[indice inf??rieur E]) de 4 V.

La photodétection est un sujet de recherche très actif encore de nos jours et l’industrie, particulièrement de la physique des hautes énergies et de l’imagerie médicale, est en quête de détecteurs avec une plus grande sensibilité, de meilleures résolutions temporelles et une plus grande densité d’intégration. Pour ces raisons, les photodiodes avalanche à photon unique (Single photon avalanche diode, ou SPAD) suscitent beaucoup d’intérêt depuis quelques années pour ses performances en temps et sa grande photosensibilité. Les SPAD sont des photodiodes avalanche opérées au-dessus de la tension de claquage et un photoporteur atteignant la région de multiplication peut à lui seul déclencher une avalanche soutenue de porteurs et entraîner le claquage de la jonction. Un circuit détecte le courant divergent et l’étouffe en abaissant la polarisation de la jonction sous la tension de claquage. Le circuit recharge ensuite la jonction en réappliquant la tension initiale permettant la détection d’un nouveau photon. Dans le but d’augmenter le nombre de photons simultanés détectables, les SPAD s’intègrent en matrice. Cependant, dans le cas où une matrice de SPAD et leurs circuits d’étouffement s’intègrent sur le même substrat, la surface photosensible devient limitée par l’espace qu’occupent les circuits d’étouffement. Dans le but d’augmenter leur région photosensible, les matrices de SPAD peuvent s’intégrer en trois dimensions (3D) avec leurs circuits d’étouffement. Ce projet porte sur le développement de matrices de SPAD en technologie CMOS HV 0,8 µm de Teledyne DALSA dédiées à une intégration 3D avec leurs circuits d’étouffement actifs. Les résultats de caractérisation montrent que les SPAD atteignent une résolution temporelle de 27 ps largeur à mi hauteur (LMH), possèdent un taux de comptage en obscurité (DCR, ou Dark Count Rate) de 3 s[indice supérieur -1]µm[indice supérieur -2] et ont une probabilité de photodétection (PDP) de 49 %. De plus, une méthode d’isolation utilisant un puits p a été développée. Les SPAD conçus avec cette méthode ont un facteur de remplissage pouvant atteindre 54 % et une probabilité de diaphonie de 6,6 % à une tension excédentaire à la tension de claquage (V[indice inférieur E]) de 4 V.

Les diodes à avalanche à photon unique (SPAD) sont utilisées pour les capteurs à temps de vol afin de déterminer la distance d'une cible. Cependant, ils sont sujets à des déclenchements parasites par des porteurs de charge générés de manière parasitaire, quantifiés en tant que taux de comptage dans l’obscurité (DCR), ce qui peut compromettre la précision de la distance mesurée. Pour résoudre ce problème, une méthodologie de simulation a été mise en place pour évaluer le DCR. Cela est réalisé en simulant la probabilité de claquage d'avalanche, intégrée avec le taux de génération de porteurs de charge à partir de défauts. Cette méthodologie permet d'identifier les sources potentielles de DCR avant stress. Pour garantir l'intégrité des mesures de distance sur une longue période, il est nécessaire de prédire le niveau de DCR dans diverses conditions d'exploitation. La méthodologie de simulation susmentionnée est utilisée pour identifier les sources potentielles de DCR après stress. Pour un modèle cinétique précis de dégradation de type porteurs chauds (HCD), il est essentiel de considérer non seulement la distribution d'énergie des porteurs, mais également la distribution de l'énergie de dissociation de la liaison Si-H à l'interface Si/SiO2. La probabilité de dissociation d'ionisation d'impact est utilisée pour modéliser le processus de création de défauts, qui présente une dépendance temporelle sous-linéaire en raison de l'épuisement progressif des précurseurs de défauts. Une mesure précise de la distance nécessite de distinguer le signal du bruit ambiant et du plancher de DCR. L'impact de DCR peut être estimé en considérant la réflectance de la cible et les conditions d'éclairage ambiant. En résumé, ce travail utilise une méthodologie de caractérisation et de simulation approfondie pour prédire le DCR dans les dispositifs de type SPAD le long de sa durée de vie, permettant ainsi d'évaluer son impact sur les mesures de distance
Single-Photon Avalanche Diode (SPAD) are used for Time-of-Flight (ToF) sensors to determine distance from a target by measuring the travel time of an emitted pulsed signal. These photodetectors work by triggering an avalanche of charge carriers upon photon absorption, resulting in a substantial amplification which can be detected. However, they are subject to spurious triggering by parasitic generated charge carriers, quantified as Dark Count Rate (DCR), which can compromise the accuracy of the measured distance. Therefore, it is crucial to identify and eliminate the potential source of DCR. To tackle this issue, a simulation methodology has been implemented to assess the DCR. This is achieved by simulating the avalanche breakdown probability, integrated with the carrier generation rate from defects. The breakdown probability can be simulated either in a deterministically, based on electric-field streamlines, or stochastically, by means of drift-diffusion simulation of the random carrier path. This methodology allows for the identification of the potential sources of pre-stress DCR by comparing simulation results to experimental data over a wide range of voltage and temperature. To ensure the accuracy of distance range measurements over time, it is necessary to predict the DCR level under various operating conditions. The aforementioned simulation methodology is used to identify the potential sources of post-stress DCR by comparing simulation results to stress experiments that evaluate the principal stress factors, namely temperature, voltage and irradiance. Furthermore, a Monte-Carlo study has been conducted to examine the device-to-device variation along stress duration. For an accurate Hot-Carrier Degradation (HCD) kinetics model, it is essential to consider not only the carrier energy distribution function but also the distribution of Si−H bond dissociation energy distribution at the Si/SiO2 interface. The number of available hot carriers is estimated from the carrier current density according to the carrier energy distribution simulated by means of a full-band Monte-Carlo method. The impact-ionization dissociation probability is employed to model the defect creation process, which exhibits sub-linear time dependence due to the gradual exhaustion of defect precursors. Accurate distance ranging requires distinguishing the signal from ambient noise and the DCR floor, and ensuring the target’s accumulated photon signal dominates over other random noise sources. An analytical formula allows to estimate the maximum distance ranging using the maximum signal strength, ambient noise level, and confidence levels. The impact of DCR can be estimated by considering the target’s reflectance and the ambient light conditions. In a nutshell, this work makes use of a in-depth characterization and simulation methodology to predict DCR in SPAD devices along stress duration, thereby allowing the assessment of its impact on distance range measurements

Ce travail porte sur la modélisation pour la simulation et la prédiction desparamètres de performance des photodiodes à avalanche polarisée en mode Geiger en technologieCMOS, ou SPADs CMOS, pour Lidars spatiaux. Ce travail de thèse vise à développerune méthodologie basée sur : des modèles de la physique du semi-conducteur, des mesuresfournissant des informations sur le procédé technologique visé et des outils commerciaux desimulation. Ceci, dans le but de simuler les paramètres de performance des SPADs en serapprochant autant que possible de la réalité du procédé technologique afin d’améliorer lesprédictions. Des SPADs ont été conçues et caractérisées de manière à acquérir les paramètresde performances et les confronter aux résultats de simulation pour valider notre approche.De plus, la conception des SPADs s’est faite en regard des spécifications Lidar du CNESet d’Airbus Defence and Space en vue d’obtenir des structures permettant d’améliorer nosconnaissances en matière de : compréhension des mécanismes physiques, conception et méthodede caractérisation des SPADs CMOS. Ceci, dans l’intention d’étudier la possibilitéd’intégrer ces détecteurs dans leurs futurs systèmes Lidars spatiaux
This work focuses on modelling for simulation and prediction purposes ofCMOS SPADs performance parameters used in spaceborne Lidars. The innovative side ofthis work lies in a new methodology based on physical models for semiconductor devices,measurements performed on the targeted CMOS process and commercial simulation tools topredict CMOS SPADs performances. This method allows to get as close as possible to theprocess reality and to improve predictions. A set of SPAD has been designed and fabricated,and is used for measurements and model validation. SPAD design has been done with respectto CNES and Airbus Defence Space Lidar specification, in order to produce devices that willimprove our knowledge in terms of understanding of the involved physical mechanisms, SPADsdesign and test method, for a possible integration within their future spaceborne Lidars

Thesis: M. Eng., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2015.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 77-78).
Single-photon avalanche diodes (SPADs) are highly sensitive photodetectors that enable LIDAR imaging at extremely low photon flux levels. While conventional image formation methods require hundreds or thousands of photon detections per pixel to suppress noise, a recent computational approach achieves comparable results when forming reflectivity and depth images from on the order of 1 photon detection per pixel. This method uses the statistics underlying photon detections, along with the assumption that depth and reflectivity are spatially correlated in natural scenes, to perform noise censoring and regularized maximum-likelihood estimation. We expand on this research by adapting the method for use with SPAD arrays, accounting for the spatial non-uniformity of imaging parameters and the effects of crosstalk. We develop statistical models that incorporate these non-idealities, and present a statistical method for censoring crosstalk detections. We show results that demonstrate the performance of our method on simulated data with a range of imaging parameters.
by Sarah Rumbley.
M. Eng.

We have studied a new optical sensor characterized by performances that will extend the capabilities of several new physical investigation techniques. Our imaging device is based on a two-dimensional array of Single Photon Avalanche Diode (SPAD), sensitive to the single photon with a subnanosecond timing precision. It is able to perform a continuous photon acquisition without the necessity to break to perform the readout process. Moreover it is not damageable by intense light sources. The proposed solution constitutes a step forward for all Time Correlated Single Photon Counting analysis, as Fluorescence Lifetime Imaging Microscopy, Dynamic Light Scattering, 3D Camera, Particle Imaging Velocimetry and Adaptive Optics. An electric characterization of the single SPAD has been carried out to perform multiple readout strategies, and an electric model has been used to perform the simulation of different two-dimensional electric array configurations. We have also deeply studied the source of the counting distortion of the single passive quenched SPAD and have been able to extend the dynamic range of four order of magnitude and to use the dead time saturation as a compression feature for data produced by our imaging sensor. The dead time compensation laws established in Literature have been extended over the steady state analysis to include the time dependent source and any type of dead time. The acquisition electronics, the sensor calibration and the imaging reconstruction algorithm have been performed on a working prototype. The device has been tested with many experimental setups, developed to evaluate the features and the limits of our technological solutions.
Abbiamo studiato un nuovo sensore ottico caratterizzato da prestazioni che estenderanno le funzionalita' di molte nuove tecniche di indagine fisica. Il nostro dispositivo si basa su una matrice bidimensionale di Single Photon Avalanche Diode (SPAD), in grado di fornire il tempo di arrivo di ogni singolo fotone con una precisione del decimo di nanosecondo. Il nostro apparato e' in grado di acquisire là ¢ arrivo dei fotoni con continuita', senza interruzioni dovute al processo di lettura, ed e' inoltre resistente a fonti di luce eccessiva che costituiscono una limitazione per i normali dispositivi a singolo fotone. La soluzione proposta costituisce un passo in avanti per tutte le analisi basate sulla correlazione temporale a singolo fotone, come la Fluorescence Lifetime Imaging Microscopy, Dynamic Light Scattering, 3D Camera, Particle Imaging Velocimetry e Adaptive Optics. Grazie allo studio delle caratteristiche elettriche del singolo SPAD e' stato possibile individuare varie strategie di lettura. Il modello elettrico sviluppato e' stato inoltre utilizzato per simulare diverse configurazioni elettriche della matrici bidimensionali di sensori. Abbiamo studiato le caratteristiche funzionali del singolo SPAD ponendo l'attenzione sui fenomeni che alterano la linearita' di ri-sposta, siamo stati cosi' in grado di estendere di quattro ordini di grandezza il suo intervallo di utilizzo, e di utilizzare la saturazione come una funzione di compressione dei dati prodotti dal sensore. Le equazioni presentate estendono la correzione degli effetti del tempo morto, gia' presenti in letteratura, dallà ¢ analisi del caso stazionario a quello delle sorgenti variabili nel tempo, e sono inoltre estendibili a qualunque configurazione di tempo morto. La produzione di un prototipo funzionante ha compreso inoltre la realizzazione dell'elettronica di acquisizione, dell'algoritmo di calibrazione del sensore e di ricostruzione delle immagini. Il dispositivo e' stato testato realizzando diversi esperimenti, che hanno permesso di valutare le caratteristiche e i limiti delle soluzioni tecnologiche adottate.

There is a pressing need to develop alternative communications links due to a number of physical phenomena, limiting the bandwidth and energy efficiency of wire-based systems or economic factors such as cost, material-supply reliability and environmental costs. Networks have moved to optical connections to reduce costs, energy use and to supply high data rates. A primary concern is that current optical-detection devices require high optical power to achieve fast data rates with high signal quality. The energy required therefore, quickly becomes a problem. In this thesis, advances in single-photon avalanche diodes (SPADs) are utilised to reduce the amount of light needed and to reduce the overall energy budget. Current high performance receivers often use exotic materials, many of which have severe environmental impact and have cost, supply and political restrictions. These present a problem when it comes to integration; hence silicon technology is used, allowing small, mass-producible, low power receivers. A reconfigurable SPAD-based integrating receiver in standard 130nm imaging CMOS is presented for links with a readout bandwidth of 100MHz. A maximum count rate of 58G photon/s is observed, with a dynamic range of ≈ 79dB, a sensitivity of ≈ −31.7dBm at 100MHz and a BER of ≈ 1x10−9. We investigate the properties of the receiver for optical communications in the visible spectrum, using its added functionality and reconfigurability to experimentally explore non-ideal influences. The all-digital 32x32 SPAD array, achieves a minimum dead time of 5.9ns, and a median dark count rate (DCR) of 2.5kHz per SPAD. High noise devices can be weighted or removed to optimise the SNR. The power requirements, transient response and received data are explored and limiting factors similar to those of photodiode receivers are observed. The thesis concludes that data can be captured well with such a device but more electrical energy is needed at the receiver due to its fundamental operation. Overall, optical power can be reduced, allowing significant savings in either transmitter power or the transmission length, along with the advantages of an integrated digital chip.

This thesis explores Single-Photon Avalanche Diodes (SPADs), which are solid-state devices for photon timing and counting, and concentrates on SPADs integrated in nano-scale CMOS. The thesis focuses on: the search for new theory regarding Geiger-mode operation; proving the utility of calibrated Technology Computer- Aided Design (TCAD) tools for accurately simulating SPADs for the first time; the investigation of how manufacture influences device operation; and the integration of high performance SPADs into CMOS which rival discrete devices. The accepted theories of SPAD operation are revisited and it is discovered that previously neglected minority carriers have many significant roles such as determining: after-pulsing, Dark Count Rate (DCR), bipolar “SPAD latch-up,” nonequilibrium DCR, and “quenching”. The “quenching” process is revisited and it is concluded that it is the “probability time” of ≈100-200ps, and not the previously thought latching current that is important. SPADs are also found to have transient negative differential resistance. The new theories of SPADs are also supported by steady-state 1D, 2D and 3D TCAD simulations as well as novel transient simulations and videos. It is demonstrated as possible to simulate DCR, Photon Detection Efficiency (PDE), guard ring performance, breakdown voltage, breakdown voltage variation, “quenching,” and transient operation of SPADs with great accuracy. The manufacture of SPADs is studied focusing on the operation and optimisation of guard rings and it is found that ion implantation induced asymmetry from the tilt and rotation/twist is critical. Where symmetric, guard rings fail first along the <100> directions due to enhanced mobility. Process integration rules are outlined for obtaining high performance SPADs in CMOS while maintaining compatibility with transistors. The minimisation of tunnelling with lightly-doped junctions and the reduction of ion implantation induced defects by additional annealing are found essential for achieving low DCR. The thesis demonstrates that it is possible to realise high performance SPADs in CMOS through the innovation of a “Deep SPAD” which achieves record PDE of ≈72% at 560nm with >40% PDE from 410-760nm, combined with 18Hz DCR, <60ps FWHM timing resolution, and <4% after-pulsing which is demonstrated to have potential for significant further improvement. The findings suggest that CMOS SPAD-based micro-systems could outperform existing photon timing and counting solutions in the future.

In order to improve the sensitivity of an optical receiver, the gain and the collection area of the photo-detectors within the receiver should be increased. Detectors with internal gain such as avalanche photodiodes (APD) are usually used to increase the sensitivity of the receiver. One problem with APDs is the sensitivity of their gain to their bias voltage, which makes them challenging to be fabricated in a standard CMOS process due to variations in their gain. However, when an APD is biased over its breakdown voltage, it is sensitive to a single photon, hence, referred to as a single photon avalanche diodes (SPAD). The SPADs are photon-counting detectors, which are less sensitive to their bias voltage, and can be integrated with rest of the electronic circuitry that form an optical receiver. An avalanche diode requires dedicated circuits to be operated in the SPAD mode. These circuits make the diode insensitive to an incident photon for a duration that is known as deadtime. Unfortunately, The collection area of the PD, APD, and SPADs are limited to their capacitance. Hence, a large photo-detector leads to a larger capacitance, which reduces the bandwidth of the receiver. In this thesis, a photon counting optical receiver based on an array of SPADs is proposed which increases the collection area with a low output capacitance. The avalanche diode and peripheral circuits which operate and readout-out the SPAD array are fabricated in the commercially available UMC 0.18 μm CMOS process. Initially, the avalanche diode is tested and characterised. A high performance circuit is then designed and tested which is able to achieve short deadtimes up to 4 ns. Once the photon counting operation of the SPAD is verified, a numerical model is developed to investigate the influence of several factors, including the deadtime, on the performance of the photon-counting detector in a communication link. Based on the simulation results, which show the advantages of an array over a single detector, a prototype detector array of 64 asynchronous SPADs is designed and tested. This array uses a high-speed readout mechanism which is inspired by the current steering digital-to-analogue converters. Bit error ratio tests (BERT) verify the photon counting capability of the proposed detector, and a bit error rate of 1E-3 has been achieved at data rate of 100 Mbps. In addition, the array of SPAD is compatible with a front-end of conventional optical receiver which uses a photodiode as a photo detector.

Les métaux nobles (Au, Ag, Pt, Ir, Pd et Ru) sont utilisés en salle blanche pour la réalisation de dispositifs électroniques ou peuvent être apportés par les équipements de fabrication (composants d’alliage par exemple). Il a été montré qu’ils pouvaient impacter fortement les dispositifs. Il est alors nécessaire de procéder au contrôle des équipements pour diagnostiquer au plus tôt une contamination. Or, il n’existe pas de technique industrielle pour leur suivi et ce à des niveaux d’au moins 5.109 at.cm-2 - recommandation ITRS. Il se pose la question de la pertinence de ces recommandations en fonction des types de dispositifs (SPAD notamment). Dans un premier temps, les travaux ont consisté à développer une technique physico-chimique pour l’analyse des métaux nobles sur silicium par VPD-DC-ICPMS. Enfin, leur dangerosité vis-à-vis des équipements et des dispositifs a été évaluée d’après leur comportement en température et le DCR généré sur SPAD
Noble metals (Au, Ag, Pt, Ir, Pd and Ru) are used for the fabrication of microelectronics devices or can be brought by manufacturing tools (alloy components for example). It is well known that these impurities are detrimental to the efficiency of the devices. This implies a real and present need for control of their introduction in clean rooms to diagnose as soon as possible a contamination. Yet, there are no industrial technique for their follow-up at levels about 5.109 at.cm-2 - ITRS recommendations. The relevance of these recommendations according to the electronic device (SPAD in particular) could be questioned. At first, this study consisted in developing a physicochemical technique for the analysis of noble metals on Si wafers by VPD-DC-ICPMS. Then, their dangerousness towards tools and devices was established according to their behavior in temperature and the DCR generated on SPAD devices

Vision has always been one of the most important cognitive tools of human beings. In this regard, the development of image sensors opens up the potential to view objects that our eyes cannot see. One of the most promising capability in some image sensors is their single-photon sensitivity that provides information at the ultimate fundamental limit of light. Time-resolved single-photon avalanche diode (SPAD) image sensors bring a new dimension as they measure the arrival time of incident photons with a precision in the order of hundred picoseconds. In addition to this characteristic, they can be fabricated in complementary metal-oxide-semiconductor (CMOS) technology enabling the integration of complex signal processing blocks at the pixel level. These unique features made CMOS SPAD sensors a prime candidate for a broad spectrum of applications. This thesis is dedicated to the optimization and characterization of quantum imagers based on the SPADs as part of the E.U. funded SUPERTWIN project to surpass the fundamental diffraction limit known as the Rayleigh limit by exploiting the spatio-temporal correlation of entangled photons. The first characterized sensor is a 32×32-pixel SPAD array, named “SuperEllen”, with in-pixel time-to-digital converters (TDC) that measure the spatial cross-correlation functions of a flux of entangled photons. Each pixel features 19.48% fill-factor (FF) in 44.64-μm pitch fabricated in a 150-nm CMOS standard technology. The sensor is fully characterized in several electro-optical experiments, in order to be used in quantum imaging measurements. Moreover, the chip is calibrated in terms of coincidence detection achieving the minimal coincidence window determined by the SPAD jitter. The second developed sensor in the context of SUPERTWIN project is a 224×272-pixel SPAD-based array called “SuperAlice”, a multi-functional image sensor fabricated in a 110-nm CMOS image sensor technology. SuperAlice can operate in multiple modes (time-resolving or photon counting or binary imaging mode). Thanks to the digital intrinsic nature of SPAD imagers, they have an inherent capability to achieve a high frame rate. However, running at high frame rate means high I/O power consumption and thus inefficient handling of the generated data, as SPAD arrays are employed for low light applications in which data are very sparse over time and space. Here, we present three zero-suppression mechanisms to increase the frame rate without adversely affecting power consumption. A row-skipping mechanism that is implemented in both SuperEllen and SuperAlice detects the absence of SPAD activity in a row to increase the duty cycle. A current-based mechanism implemented in SuperEllen ignores reading out a full frame when the number of triggered pixels is less than a user-defined value. A different zero-suppression technique is developed in the SuperAlice chip that is based on jumping through the non-zero pixels within one row. The acquisition of TDC-based SPAD imagers can be speeded up further by storing and processing events inside the chip without the need to read out all data. An on-chip histogramming architecture based on analog counters is developed in a 150-nm CMOS standard technology. The test structure is a 16-bin histogram with 9 bit depth for each bin. SPAD technology demonstrates its capability in other applications such as automotive that demands high dynamic range (HDR) imaging. We proposed two methods based on processing photon arrival times to create HDR images. The proposed methods are validated experimentally with SuperEllen obtaining >130 dB dynamic range within 30 ms of integration time and can be further extended by using a timestamping mechanism with a higher resolution.

Vision has always been one of the most important cognitive tools of human beings. In this regard, the development of image sensors opens up the potential to view objects that our eyes cannot see. One of the most promising capability in some image sensors is their single-photon sensitivity that provides information at the ultimate fundamental limit of light. Time-resolved single-photon avalanche diode (SPAD) image sensors bring a new dimension as they measure the arrival time of incident photons with a precision in the order of hundred picoseconds. In addition to this characteristic, they can be fabricated in complementary metal-oxide-semiconductor (CMOS) technology enabling the integration of complex signal processing blocks at the pixel level. These unique features made CMOS SPAD sensors a prime candidate for a broad spectrum of applications. This thesis is dedicated to the optimization and characterization of quantum imagers based on the SPADs as part of the E.U. funded SUPERTWIN project to surpass the fundamental diffraction limit known as the Rayleigh limit by exploiting the spatio-temporal correlation of entangled photons. The first characterized sensor is a 32×32-pixel SPAD array, named “SuperEllen”, with in-pixel time-to-digital converters (TDC) that measure the spatial cross-correlation functions of a flux of entangled photons. Each pixel features 19.48% fill-factor (FF) in 44.64-μm pitch fabricated in a 150-nm CMOS standard technology. The sensor is fully characterized in several electro-optical experiments, in order to be used in quantum imaging measurements. Moreover, the chip is calibrated in terms of coincidence detection achieving the minimal coincidence window determined by the SPAD jitter. The second developed sensor in the context of SUPERTWIN project is a 224×272-pixel SPAD-based array called “SuperAlice”, a multi-functional image sensor fabricated in a 110-nm CMOS image sensor technology. SuperAlice can operate in multiple modes (time-resolving or photon counting or binary imaging mode). Thanks to the digital intrinsic nature of SPAD imagers, they have an inherent capability to achieve a high frame rate. However, running at high frame rate means high I/O power consumption and thus inefficient handling of the generated data, as SPAD arrays are employed for low light applications in which data are very sparse over time and space. Here, we present three zero-suppression mechanisms to increase the frame rate without adversely affecting power consumption. A row-skipping mechanism that is implemented in both SuperEllen and SuperAlice detects the absence of SPAD activity in a row to increase the duty cycle. A current-based mechanism implemented in SuperEllen ignores reading out a full frame when the number of triggered pixels is less than a user-defined value. A different zero-suppression technique is developed in the SuperAlice chip that is based on jumping through the non-zero pixels within one row. The acquisition of TDC-based SPAD imagers can be speeded up further by storing and processing events inside the chip without the need to read out all data. An on-chip histogramming architecture based on analog counters is developed in a 150-nm CMOS standard technology. The test structure is a 16-bin histogram with 9 bit depth for each bin. SPAD technology demonstrates its capability in other applications such as automotive that demands high dynamic range (HDR) imaging. We proposed two methods based on processing photon arrival times to create HDR images. The proposed methods are validated experimentally with SuperEllen obtaining >130 dB dynamic range within 30 ms of integration time and can be further extended by using a timestamping mechanism with a higher resolution.

Ce travail a pour objectif la conception, la simulation, la modélisation et la caractérisation électrique de diodes à avalanche à photon unique (Single Photon Avalanche Diodes - SPAD) intégrées dans une technologie CMOS Fully Depleted Silicon on Insulator - FDSOI. Les SPAD sont des diodes (jonctions PN) polarisées en inverse au-delà de la tension de claquage, fonctionnant dans le mode Geiger. Grace à leur haute sensibilité et rapidité, les SPAD sont utiles pour plusieurs applications, telles que les mesures de temps de vol (Time of Flight - ToF), l’imagerie médicale (Fluorescence Lifetime Imaging Microscopy - FLIM), ainsi que la détection de particules chargées, dans le domaine de la physique de haute énergie. L’intégration de SPAD dans une technologie CMOS FDSOI permet d’obtenir une intégration 3D monolithique intrinsèque avec la diode sous l’oxyde enterré, et l’électronique associée dans le film silicium, en optimisant ainsi le facteur de remplissage. Afin d’analyser le comportement des SPAD FDSOI, plusieurs cellules ont été conçues, respectant les principales règles de dessin imposées par la fonderie, mais présentant des variantes structurelles telles que la zone d'intégration, la géométrie, la distance de garde et le circuit d’étouffement. Des simulations TCAD et des calculs analytiques ont été effectués afin d'estimer les principales figures du mérite de SPAD. Plusieurs modèles d'avalanche et de génération de porteurs ont été étudiés pour une meilleure adaptation du modèle simulé aux dispositifs fabriqués. Des caractérisations électriques ont été réalisées pour estimer des paramètres importants tels que la tension de claquage, le taux de comptage dans l'obscurité (DCR) et la réponse en l'électroluminescence. Bien que les résultats obtenus restent inférieurs par rapport à l'état de l’art, la faisabilité d’intégration de SPAD dans une technologie FDSOI a été démontrée comme preuve de concept, mais des améliorations sont nécessaires et certaines pistes sont proposées
This work aims at the design, simulation, modelling and electrical characterization of Single Photon Avalanche Diodes (SPAD) in an advanced Fully Depleted Silicon on Insulator (FDSOI) technology. SPADs are PN junctions reversed bias above breakdown voltage, operating in the so-called Geiger mode. Such an implementation should provide an intrinsic monolithic integration of those devices, along with their mandatory associated electronics, thanks to the buried oxide layer present in that technology, optimizing fill factor. Due to its high sensitivity, SPAD are useful for several applications, such as Time of Flight (ToF) and Fluorescence Lifetime Imaging Microscopy (FLIM) measurements, as well as the detection of charged particles, in high-energy physics domain. The designed cells follow the main design rules imposed by the foundry and present variations in aspect as integration zone, geometry, guard distance and quenching circuit. TCAD simulations were performed in order to estimate some of the SPAD main Figures of Merit. Several avalanche and carrier generation models were studied for better adapting the simulated model to the actual fabricated devices. Electrical characterizations were realized for estimating important parameters such as breakdown voltage, Dark Count Rate (DCR) and electroluminescence response. Although the obtained results are still poor when compared to State-of-the-Art, its feasibility was demonstrated and can be used as a proof of concept, at the same time that improvements are proposed

Fluorescence based analysis is a fundamental research technique used in the life sciences. However, conventional fluorescence intensity measurements are prone to misinterpretation due to illumination and fluorophore concentration non-uniformities. Thus, there is a growing interest in time-resolved fluorescence detection, whereby the characteristic fluorescence decay time-constant (or lifetime) in response to an impulse excitation source is measured. The sensitivity of a sample’s lifetime properties to the micro-environment provides an extremely powerful analysis tool. However, current fluorescence lifetime analysis equipment tends to be bulky, delicate and expensive, thereby restricting its use to research laboratories. Progress in miniaturisation of biological and chemical analysis instrumentation is creating low-cost, robust and portable diagnostic tools capable of high-throughput, with reduced reagent quantities and analysis times. Such devices will enable point-of-care or in-the-field diagnostics. It was the ultimate aim of this project to produce an integrated fluorescence lifetime analysis system capable of sub-nano second precision with an instrument measuring less than 1cm3, something hitherto impossible with existing approaches. To accomplish this, advances in the development of AlInGaN micro-LEDs and high sensitivity CMOS detectors have been exploited. CMOS allows electronic circuitry to be integrated alongside the photodetectors and LED drivers to produce a highly integrated system capable of processing detector data directly without the need for additional external hardware. In this work, a 16x4 array of single-photon avalanche diodes (SPADs) integrated in a 0.35μm high-voltage CMOS technology has been implemented which incorporates two 9-bit, in-pixel time-gated counter circuits, with a resolution of 400ps and on-chip timing generation, in order to directly process fluorescence decay data. The SPAD detector can accurately capture fluorescence lifetime data for samples with concentrations down to 10nM, demonstrated using colloidal quantum dot and conventional fluorophores. The lifetimes captured using the on-chip time gated counters are shown to be equivalent to those processed using commercially available external time-correlated single-photon counting (TCSPC) hardware. A compact excitation source, capable of producing sub-nano second optical pulses, was designed using AlInGaN micro-LEDs bump-bonded to a CMOS driver backplane. A series of driver array designs are presented which are electrically contacted to an equivalent array of micro-LEDs emitting at a wavelength of 370nm. The final micro-LED driver design is capable of producing optical pulses of 300ps in width (full width half maximum, FWHM) and a maximum DC optical output power of 550μW, this is, to the best of our knowledge, the shortest reported optical pulse from a CMOS driven micro-LED device. By integrating an array of CMOS SPAD detectors and an array of CMOS driven AlInGaN micro-LEDs, a complete micro-system for time-resolved fluorescence analysis has been realised. Two different system configurations are evaluated and the ability of both topologies to accurately capture lifetime data is demonstrated. By making use of standard CMOS foundry technologies, this work opens up the possibility of a low-cost, portable chemical/bio-diagnostic device. These first-generation prototypes described herein demonstrate the first time-resolved fluorescence lifetime analysis using an integrated micro-system approach. A number of possible design improvements have been identified which could significantly enhance future device performance resulting in increased detector and micro-LED array density, improved time-gate resolution, shorter excitation pulse widths with increased optical output power and improved excitation light filtering. The integration of sample handling elements has also been proposed, allowing the sample of interest to be accurately manipulated within the micro-environment during investigation.

La genèse des travaux présentés dans ce mémoire se situe dans le domaine de l'astrophysique des très hautes énergies. Il y a un siècle les scientifiques de la planète ont identifié un nouveau type de messagers venant de l'espace : les rayons cosmiques. Ce rayonnement est constitué de particules (photons et autres) de très haute énergie qui bombardent la terre en permanence. Le passage de rayonnements cosmiques dans l'atmosphère terrestre se traduit par la génération de brefs éclairs lumineux (5ns) d'une intensité très faible (1pW) : le flash Tcherenkov, devenant alors visible du sol.

Dans l'état de l'art le meilleur détecteur de lumière est aujourd'hui le Photomultiplicateur (PMT), grâce à ses caractéristiques de sensibilité et de vitesse. Mais il présente quelques inconvénients : faible efficacité quantique, coût, poids etc. Nous présentons dans cette thèse une nouvelle technologie alternative : les compteurs de photons sur semi-conducteur, constitués de photodiodes polarisées en mode Geiger.
Ce mode de fonctionnement permet d'obtenir un effet de multiplication au moins identique à celui des PMT. Un modèle physique et électrique a été développé pour reproduire le comportement de ce détecteur.
Nous présentons ensuite dans ce travail de thèse un procédé technologique original permettant la réalisation de ces dispositifs dans la centrale de technologie du LAAS-CNRS, avec la simulation de chaque opération du processus.
Nous avons mis au point une fiche pour la caractérisation électrique des dispositifs, du mode statique au mode dynamique, et vérifié la conformité aux simulations SILVACO, et au modèle initial. Les résultats obtenus sont déjà excellents, compte tenu qu'il s'agit d'une première étape de prototypage, et comparables avec les résultats publiés dans la littérature.
Ces composants sur silicium peuvent intervenir dans toutes les applications où il y a un photomultiplicateur, et le remplacer. Les applications sont donc très vastes et la croissance du marché très rapide. Nous présentons une première expérience d'astrophysique installée au Pic du Midi qui a détecté des flashs Tcherenkov de rayons cosmiques avec cette nouvelle technologie à semi-conducteur.

With data throughput increasing exponentially in wireless communication networks, the limited radio frequency (RF) spectrum is unable to meet the future data rate demand. As a promising complementary approach, optical wireless communication (OWC) has gained significant attention since its licence-free light spectrum provides a considerable amount of communication bandwidth. In conventional OWC systems, the information-carried signal has to be real-valued and non-negative due to the incoherent light output of the conventional optical transmitter, light emitting diode (LED). Therefore, an intensity modulation and direct detection (IM/DD) system is used for establishing the OWC link. Some modified orthogonal frequency division multiplexing (OFDM) schemes have been proposed to achieve suitable optical signals. In previous research, three OFDM-based schemes have been presented, including DC-biased optical orthogonal frequency division multiplexing (DCO-OFDM), asymmetrically clipped optical orthogonal frequency division multiplexing (ACO-OFDM) and unipolar orthogonal frequency division multiplexing (U-OFDM). Basic concepts of SPAD receivers are studied and a novel application in OWC is proposed for a permanent downhole monitoring (PDM) system in the gas and oil industry. In this thesis, a complete model of the SPAD-based OWC system is presented, including some related SPAD metrics, the photon counting process in SPAD and a specific nonlinear distortion caused by passive quenching (PQ) and active quenching (AQ) recharged circuits. Moreover, a practical SPAD-based visible light communication (VLC) system and its theoretical analysis are presented in a long-distance gas pipe with a battery-powered LED and a basic on-off keying (OOK) modulation scheme. In this thesis, two novel optical orthogonal frequency division multiplexing (O-OFDM) technologies are proposed: non-DC-biased orthogonal frequency division multiplexing (NDCOFDM) and OFDM with single-photon avalanche diode (SPAD). The former is designed for optical multiple-input multiple-output (O-MIMO) systems based on the optical spatial modulation (OSM) technique. In NDC-OFDM, signs of modulated O-OFDM symbols and absolute values of the symbols are separately transmitted by different information carrying units. This scheme can eliminate clipping distortion in DCO-OFDM and achieve high power efficiency. Furthermore, as the indices of transmitters carry extra information bits, NDC-OFDM gives a significant improvement in spectral efficiency over ACO-OFDM and U-OFDM. In this thesis, SPAD-based OFDM systems with DCO-OFDM and ACO-OFDM are presented and analysed by considering the nonlinear distortion effect of PQ SPAD and AQ SPAD. A comprehensive digital signal processing of SPAD-based OFDM is shown and theoretical functions of the photon counting distribution in PQ SPAD and AQ SPAD are given. Moreover, based on Bussgang theorem, a conventional method for analysing memoryless distortion, close-formed bit-error rate (BER) expressions of SPAD-based OFDM are derived. Furthermore, SPAD-based OFDM is compared with conventional photo-diode (PD) based OFDM systems, and a gain of 40 dB in power efficiency is observed.

FLIM is branch of microscopy mainly used in biology which is quickly improving thanks to a rapid enhancement of instrumentation and techniques enabled by new sensors. In FLIM, the most precise method of measuring fluorescent decays is called TCSPC. High voltage PMT detection devices together with costly and bulky optical setups which scan the sample are usually required in TCSPC instrumentation. SPADs have enabled a big improvement in TCSPC measurement setup, providing a CMOS compatible device which can be designed in wide arrays format. However, sensors providing in-pixel TCSPC do not scale in size and in large array like the time-gated SPAD pixel sensors do. Time-gated pixels offer a less precise lifetime estimation, discarding any photon information outside a given time window, but this loss in photon-efficiency is offset by gains in pixel size. This work is aimed at the development of a wide field TCSPC sensor with a pixel size and fill factor able to reduce the cost of such devices and to obtain a high resolution time-resolved fluorescence image in the shortest time possible. The study focuses on SPAD and pixel design required to maximise the fill factor in sub 10 μm pixel pitch. Multiple pixel designs are proposed in order to reduce pixel area and so enable affordable wide array TCSPC systems. The first proposed pixel performs the CMM lifetime estimation in order to reduce the frame rate needed to stream the data out of the SPAD array. This pixel is designed in a 10 μm pitch and attains with the most aggressive design a fill factor of 10:17 %. A second design proposes an analogue TCSPC which consists in a S/H TAC circuitry. This simpler pixel can achieve a higher fill factor of 19:63% as well as smaller pitch of 8 μm thanks to the adoption of SPAD n-well and electronics area sharing. This last design is implemented in a 320 x 256 SPAD array in which is included part of a novel ADC aimed at reduction of the processing time required to build a TCSPC histogram. A more conventional analogue readout is used to evaluate the pixel performance as well as a more fine TCSPC histogram. The device was used to measure the fluorescence lifetime of green micro-spheres while the 2b flash ADC is used to demonstrate rapid resolution and separation of two different fluorescence decays.

Cette thèse porte sur une famille de photo-détecteurs appelés SPAD pour Single Photon Avalanche Diodes qui sont des jonctions PN polarisées en inverse au-delà de la tension de claquage. Les diodes SPADs sont reconnues pour présenter de très bonnes performances en détection de faibles flux lumineux avec une réponse extrême rapide. Afin d’améliorer l’efficacité de détection dans le proche infrarouge de diodes SPAD sur silicium, les objectifs de la thèse sont de concevoir, fabriquer et caractériser une nouvelle génération de photodiodes SPADs dans une technologie CMOS 40nm en intégrant une cavité de germanium. Les travaux menés comportent i) un volet conception en utilisant des outils de simulation TCAD pour proposer une architecture originale optimisée, ii) le développement du flot complet du procédé technologique avec la création de nouvelles briques telles que la gravure de la cavité et l’épitaxie de germanium dopé in-situ, 3) la caractérisation électro-optique des composants issus des premiers lots fabriqués. Les analyses et interprétations des résultats obtenus révèlent la difficulté technologique pour réaliser une hétérojonction silicium-germanium sans défauts et une couche germanium de qualité. Néanmoins, les mesures réalisées ont démontré la capacité de cette nouvelle famille de SPAD à cavité de germanium sur plateforme silicium pour détecter les flux jusqu’à 1300nm, démontrant un fort potentiel applicatif pour les applications d’aide à la navigation
This thesis deals with a family of photo-detectors called SPAD for Single Photon Avalanche Diodes which are a PN junctions reverse biased beyond the breakdown voltage. SPADs diodes are known to have very good performance in detecting low light fluxes with an extremely fast response. In order to improve the near infrared detection efficiency of SPAD diodes on silicon, the objectives of the thesis are to design, manufacture and characterize a new generation of SPAD photodiodes in 40nm CMOS technology by integrating a germanium cavity. The work carried out includes i) design and simulation using TCAD tools to propose an optimized original architecture, ii) development of the process flow in industrial imager technological with the creation of new bricks such as etch of the cavity and epitaxy of germanium in-situ doped 3) the electro-optical characterization of the manufactured devices. The results obtained reveal technological difficulty to produce a silicon-germanium heterojunction without defects. Nevertheless, the measurements carried out demonstrated the ability of this new family of germanium cavity SPADs on a silicon platform to detect wavelengths up to 1300nm, demonstrating a strong potential for time of light applications

The Silicon Photomultiplier (SiPM) is a novel solid state photon counting detector consisting of a parallel array of avalanche photodiodes biased beyond their breakdown voltage. It has known a fast development in the last few years as a possible alternative to vacuum photomultiplier tubes (PMTs) and conventional avalanche photodiodes (APDs). Indeed, current research in photodetectors is directed toward an increasing miniaturization of the pixel size, thus both improving the spatial resolution and reducing the device dimensions. SiPMs show high photon detection efficiency in the visible and near infrared range, low power consumption, high gain, ruggedness, compact size, excellent single-photon response, fast rise time and reduced sensitivity with temperature, voltage fluctuations, and magnetic fields. Furthermore, solid-state technology owns the typical advantages of the planar integration process, therefore, they can be manufactured at low costs and with high reproducibility. SiPMs performances in photon counting regime have been deeply investigated in literature, using picosecond pulsed lasers. In this regime, they can be used in applications like positron emission tomography, magnetic resonance imaging, nuclear physics instrumentation, high energy physics. An optical characterization performed via continuous wave (CW) sources has seldom been reported even though this kind of excitation seems to be very useful in several fields such as low power measurements, near-infrared spectroscopy and immunoassay tests. In this Thesis, I perform an electrical and optical analysis of two novel classes of SiPMs in the CW regime. After a brief introduction about the SiPM operating principle, parameters and properties (Chapter 1), I describe my responsivity measurements made with an incident optical power down to tenths of picowatts, monitoring the temperature of the device packages, and on a spectrum ranging from ultraviolet to near infrared (Chapter 2). These measurements allowed to define an innovative criterion to establish the conditions necessary for the device to be usable in CW regime. Chapter 3 continues with an investigation of the SiPM signal-to-noise ratio. Measurements employed a 10 Hz equivalent noise bandwidth, around a tunable reference frequency in the range 1 - 100 kHz, and were performed varying the applied bias and the temperature of the SiPM package. These results were compared with similar measurements performed on a PMT. Once the SiPM is characterized, Chapter 4 reports an innovative application: an optical characterization of a class of photonic crystals infiltrated with a new ethanol responsive hydrogel employing the SiPM as a reference photodetector. This activity shows innovative developments for the ethanol sensing to be applied into inexpensive and minimally invasive breathalyzers. Finally, Appendix A shows an electro-optical characterization of a novel class of Silicon Carbide (SiC) vertical Schottky UV detectors. I performed responsivity measurements as a function of the wavelength and the applied bias, varying the temperature of the SiC package, in the 200 - 400 nm range. The results of this work show a new approach to investigate the SiPM capabilities, the CW regime, demonstrating its outstanding performances and innovative applications. This Thesis was made in collaboration with the "Advanced Sensors Development Group" of STMicroelectronics and partially supported by the Project HIGH PROFILE (HIGH-throughput PROduction of FunctIonaL 3D imagEs of the brain), which is funded by the European Community under the ARTEMIS Joint Undertaking scheme.
The Silicon Photomultiplier (SiPM) is a novel solid state photon counting detector consisting of a parallel array of avalanche photodiodes biased beyond their breakdown voltage. It has known a fast development in the last few years as a possible alternative to vacuum photomultiplier tubes (PMTs) and conventional avalanche photodiodes (APDs). Indeed, current research in photodetectors is directed toward an increasing miniaturization of the pixel size, thus both improving the spatial resolution and reducing the device dimensions. SiPMs show high photon detection efficiency in the visible and near infrared range, low power consumption, high gain, ruggedness, compact size, excellent single-photon response, fast rise time and reduced sensitivity with temperature, voltage fluctuations, and magnetic fields. Furthermore, solid-state technology owns the typical advantages of the planar integration process, therefore, they can be manufactured at low costs and with high reproducibility. SiPMs performances in photon counting regime have been deeply investigated in literature, using picosecond pulsed lasers. In this regime, they can be used in applications like positron emission tomography, magnetic resonance imaging, nuclear physics instrumentation, high energy physics. An optical characterization performed via continuous wave (CW) sources has seldom been reported even though this kind of excitation seems to be very useful in several fields such as low power measurements, near-infrared spectroscopy and immunoassay tests. In this Thesis, I perform an electrical and optical analysis of two novel classes of SiPMs in the CW regime. After a brief introduction about the SiPM operating principle, parameters and properties (Chapter 1), I describe my responsivity measurements made with an incident optical power down to tenths of picowatts, monitoring the temperature of the device packages, and on a spectrum ranging from ultraviolet to near infrared (Chapter 2). These measurements allowed to define an innovative criterion to establish the conditions necessary for the device to be usable in CW regime. Chapter 3 continues with an investigation of the SiPM signal-to-noise ratio. Measurements employed a 10 Hz equivalent noise bandwidth, around a tunable reference frequency in the range 1 - 100 kHz, and were performed varying the applied bias and the temperature of the SiPM package. These results were compared with similar measurements performed on a PMT. Once the SiPM is characterized, Chapter 4 reports an innovative application: an optical characterization of a class of photonic crystals infiltrated with a new ethanol responsive hydrogel employing the SiPM as a reference photodetector. This activity shows innovative developments for the ethanol sensing to be applied into inexpensive and minimally invasive breathalyzers. Finally, Appendix A shows an electro-optical characterization of a novel class of Silicon Carbide (SiC) vertical Schottky UV detectors. I performed responsivity measurements as a function of the wavelength and the applied bias, varying the temperature of the SiC package, in the 200 - 400 nm range. The results of this work show a new approach to investigate the SiPM capabilities, the CW regime, demonstrating its outstanding performances and innovative applications. This Thesis was made in collaboration with the "Advanced Sensors Development Group" of STMicroelectronics and partially supported by the Project HIGH PROFILE (HIGH-throughput PROduction of FunctIonaL 3D imagEs of the brain), which is funded by the European Community under the ARTEMIS Joint Undertaking scheme.

De nombreuses applications en sciences nucléaires bénéficieraient d’un détecteur possédant une précision temporelle de 10 ps largeur à mi-hauteur à la mesure d’un photon unique. Par exemple, le projet de Time-Imaging Calorimeter en cours de conception au CERN requiert un détecteur possédant une telle précision temporelle afin de mesurer le temps de vol (TDV) et la trajectoire des particules émises lors des collisions dans les expériences du Large Hadron Collider (LHC), ce qui permet d’identifier ces dites particules. De plus, un détecteur possédant une précision temporelle de l’ordre de 10 ps permettra la mitigation de l’empilement des événements. Un second exemple est la tomographie d’émission par positrons (TEP), une modalité d’imagerie médicale non-invasive qui mesure la distribution d’un traceur radioactif afin d’étudier et détecter le cancer. Dans le but de développer un scanner TEP temps réel, le groupe de recherche en appareillage médical de Sherbrooke (GRAMS) travaille sur l’intégration de la mesure du TDV de l’interaction TEP. Les meilleures performances actuelles des détecteurs TEP se situent aux alentours de 150 ps, ce qui n’est pas suffisant pour intégrer le TDV dans un scanner TEP préclinique. Cette mesure exige une résolution temporelle TEP de l’ordre de 10 ps. La solution proposée par le GRAMS est de développer un module de comptage monophotonique (MCMP) 3D qui est composé d’une matrice de photodiodes avalanches monophotoniques (PAMP) reliée par des interconnexions verticales (TSV) à une matrice de circuits de lecture composée d’un circuit d’étouffement et d’un convertisseur temps-numérique. Ce détecteur permet donc de mesurer précisément le temps d’arrivée de chaque photon détecté. Ce document présente la conception du circuit d’étouffement réalisé en technologie CMOS 65 nm de TSMC (Taiwan Semiconductor Manufacturing Company) intégré à chaque pixel de 50 × 50 µm2 dans un MCMP 3D. Afin de répondre au besoin de précision temporelle de 10 ps dans un détecteur 3D, le circuit proposé est un circuit d’étouffement passif avec une recharge active possédant un amplificateur opérationnel en boucle ouverte à titre de comparateur de tension. L’amplificateur opérationnel utilisé possède un seuil ajustable de 0 à 2,5 V afin d’être en mesure d’évaluer le seuil optimal pour la mesure de gigue temporelle avec une PAMP. La taille finale du circuit d’étouffement est de 18 × 30 µm2 incluant l’amplificateur qui est d’une taille de 13 × 8 µm2, ce qui représente respectivement environ 22% et 4% de la taille totale du pixel. Le circuit d’étouffement possède une gigue temporelle de 4 ps largeur à mi-hauteur (LMH). Les résultats obtenus prouvent qu’il est possible d’intégrer de l’électronique de lecture de PAMP dans un MCMP 3D possédant des performances temporelles sous les 10 ps.

Le Groupe de Recherche en Appareillage Médical de Sherbrooke (GRAMS) travaille actuellement sur un programme de recherche portant sur des photodiodes à avalanche monophotoniques (PAMP) opérées en mode Geiger en vue d'une application à la tomographie d’émission par positrons (TEP). Pour opérer dans ce mode, la PAMP, ou SPAD selon l’acronyme anglais (Single Photon Avalanche Diode), requiert un circuit d'étouffement (CE) pour, d’une part, arrêter l’avalanche pouvant causer sa destruction et, d’autre part, la réinitialiser en mode d’attente d’un nouveau photon. Le rôle de ce CE comprend également une électronique de communication vers les étages de traitement avancé de signaux. La performance temporelle optimale du CE est réalisée lorsqu’il est juxtaposé à la PAMP. Cependant, cela entraîne une réduction de la surface photosensible ; un élément crucial en imagerie. L’intégration 3D, à base d'interconnexions verticales, offr une solution élégante et performante à cette problématique par l’empilement de circuits intégrés possédant différentes fonctions (PAMP, CE et traitement avancé de signaux). Dans l’approche proposée, des circuits d’étouffement de 50 [mu]m x 50 [mu]m réalisés sur une technologie CMOS 130 nm 3D Tezzaron, contenant chacun 112 transistors, sont matricés afin de correspondre à une matrice de PAMP localisée sur une couche électronique supérieure. Chaque circuit d'étouffement possède une gigue temporelle de 7,47 ps RMS selon des simulations faites avec le logiciel Cadence. Le CE a la flexibilité d'ajuster les temps d'étouffement et de recharge pour la PAMP tout en présentant une faible consommation de puissance ( ~ 0,33 mW à 33 Mcps). La conception du PAMP nécessite de supporter des tensions supérieures aux 3,3 V de la technologie. Pour répondre à ce problème, des transistors à drain étendu (DEMOS) ont été réalisés. En raison de retards de production par les fabricants, les circuits n’ont pu être testés physiquement par des mesures. Les résultats de ce mémoire sont par conséquent basés sur des résultats de simulations avec le logiciel Cadence.

Résumé : Les photodiodes à avalanche monophotonique (SPAD) sont d'intérêts pour les applications requérant la détection de photons uniques avec une grande résolution temporelle, comme en physique des hautes énergies et en imagerie médicale. En fait, les matrices de SPAD, souvent appelés photomultiplicateurs sur silicium (SiPM), remplacent graduellement les tubes photomultiplicateurs (PMT) et les photodiodes à avalanche (APD). De plus, il y a une tendance à utiliser les matrices de SPAD en technologie CMOS afin d'obtenir des pixels intelligents optimisés pour la résolution temporelle. La fabrication de SPAD en technologie CMOS commerciale apporte plusieurs avantages par rapport aux procédés optoélectroniques comme le faible coût, la capacité de production, l'intégration d'électronique et la miniaturisation des systèmes. Cependant, le défaut principal du CMOS est le manque de flexibilité de conception au niveau de l'architecture du SPAD, causé par le caractère fixe et standardisé des étapes de fabrication en technologie CMOS. Un autre inconvénient des matrices de SPAD CMOS est la perte de surface photosensible amenée par la présence de circuits CMOS. Ce document présente la conception, la caractérisation et l'optimisation de SPAD fabriqués dans une technologie CMOS commerciale (Teledyne DALSA 0.8µm HV CMOS - TDSI CMOSP8G). Des modifications de procédé sur mesure ont été introduites en collaboration avec l'entreprise CMOS pour optimiser les SPAD tout en gardant la compatibilité CMOS. Les matrices de SPAD produites sont dédiées à être intégrées en 3D avec de l'électronique CMOS économique (TDSI) ou avec de l'électronique CMOS submicronique avancée, produisant ainsi un SiPM 3D numérique. Ce SiPM 3D innovateur vise à remplacer les PMT, les APD et les SiPM commerciaux dans les applications à haute résolution temporelle. L'objectif principal du groupe de recherche est de développer un SiPM 3D avec une résolution temporelle de 10 ps pour usage en physique des hautes énergies et en imagerie médicale. Ces applications demandent des procédés fiables avec une capacité de production certifiée, ce qui justifie la volonté de produire le SiPM 3D avec des technologies CMOS commerciales. Ce mémoire étudie la conception, la caractérisation et l'optimisation de SPAD fabriqués en technologie TDSI-CMOSP8G.
Abstract : Single Photon Avalanche Diodes (SPAD) generate much interest in applications which require single photon detection and excellent timing resolution, such as high energy physics and medical imaging. In fact, SPAD arrays such as Silicon PhotoMultipliers (SiPM) are gradually replacing PhotoMultiplier Tubes (PMT) and Avalanche PhotoDiodes (APD). There is now a trend moving towards SPAD arrays in CMOS technologies with smart pixels control for high timing demanding applications. Making SPAD in commercial CMOS technologies provides several advantages over optoelectronic processes such as lower costs, higher production capabilities, easier electronics integration and system miniaturization. However, the major drawback is the lack of flexibility when designing the SPAD architecture because all fabrication steps are fixed by the CMOS technology used. Another drawback of CMOS SPAD arrays is the loss of photosensitive areas caused by the CMOS circuits integration. This document presents SPAD design, characterization and optimization made in a commercial CMOS technology (Teledyne DALSA 0.8 µm HV CMOS - TDSI CMOSP8G). Custom process variations have been performed in partnership with the CMOS foundry to optimize the SPAD while keeping the CMOS line compatibility. The realized SPAD and SPAD arrays are dedicated to 3D integration with either low-cost TDSI CMOS electronics or advanced deep sub-micron CMOS electronics to perform a 3D digital SiPM (3D-SiPM). The novel 3D-SiPM is intended to replace PMT, APD and commercially available SiPM in timing demanding applications. The group main objective is to develop a 10 ps timing resolution 3D-SiPM for use in high energy physics and medical imaging applications. Those applications require reliable technologies with a certified production capability, which justifies the actual effort to use commercial CMOS line to develop our 3D-SiPM. This dissertation focuses on SPAD design, characterization and optimization made in the TDSI-CMOSP8G technology.

碩士
國立交通大學
電子工程學系 電子研究所
101
In this work, the photon detection performance of single-photon avalanche diodes (SPADs) fabricated in the high-voltage (HV) 0.25-μm CMOS technology is studied and discussed in details, including photon detection probability (PDE) and jitter. The devices measured in this work exhibited a very low dark count rate in a previous study. The wavelength-dependent PDEs are measured under various excess voltages. The maximun PDE of about 14.2% at 510 nm is obtained. By squeezing the incident light spot into about 1-μm, the 2-D spatial distribution of photo-counts in the circular active area are mapped automatically. The 2-D mappings of photo-counts reveal a clear ring-like non-uniformity. The non-uniform distribution becomes more significant with a shorter wavelength and a higher bias voltage. Simulations with TCAD are performed to understand the spatial distributions of electric field inside the active region. It is found that the arrangement of contact pad and connection metal line affects the electric field underneath, which results the non-uniformity of photo-counts. In addition, by using pulsed laser diodes at 405 and 782 nm and a time-correlated photon-counting card, the jitter distributions of the devices under various bias voltages are measured and analyzed. At last, by using the same technology, two new structures of SPADs with opposite doping types are designed and simulated to study their transient photo response, which would be helpful for achieving low jitter SPADs in the future.

碩士
國立交通大學
電子研究所
106
To enhance detection efficiency and image resolution, high fill-factor array of single-photon avalanche diodes (SPADs) is applied by shortening the distance between devices. However, crosstalk between adjacent SPADs becomes an issue in this decade. In this thesis, an extensive study on various aspects of crosstalk in a CMOS SPAD array, including device structure, device-to-device distance, bias voltage, and its timing characteristics, is presented. According to the experimental results and a simple model fitting, we deduce that the crosstalk between CMOS SPADs is dominated by direct optical coupling. Timing characteristics of crosstalk support our explanation and provide an additional angle of observation on its mechanism. For single SPADs, by applying a proper doping concentration profile in TCAD simulation, experimental temperature-dependent breakdown voltages and C-V curves are fitted in good consistence. The size effect of photon-detection probability (PDP) is investigated by using 2-D photo-count mapping. The same simulation method and doping profiles tells that the PDP non-uniformity is caused by the guard-ring induced electric field lowering. A doping profile for guard-ring region is proposed to ease this problem. This work is highly valuable for SPAD array design for various imaging applications in the future.

碩士
國立交通大學
電子工程學系 電子研究所
104
In this work, the afterpulsing effect in single photon avalanche diodes (SPADs) fabricated by TSMC 25HV (high voltage) CMOS process are studied. A new method for evaluating afterpulsing effect has been proposed and demonstrated. Different from conventional method requiring photon correlation measurement and short-pulsed light source, the proposed scheme is simply a measurement of dark count rate (DCR) distribution. Because the afterpulsing events correlate with their parent breakdowns, the DCR distribution deviates from the original Poisson one, which can be used to evaluate afterpulsing probability (APP). To demonstrate the validity of our method, we established a system to measure the temperature-dependent DCRs of a SPAD and analyzed their distribution. At low temperature, as the afterpulsing effect worsens, a clear non-Poisson distribution of DCRs is observed. A quantitative simulation has been performed to find out the relation between the DCR distribution and the APP. Our method is useful for evaluating APPs either in single SPADs or in circuit-integrated SPAD arrays.

碩士
國立交通大學
電子研究所
100
In this work, we study single-photon-avalanche-diodes (SPADs) with an active quenching circuit (AQC) by using the standard 0.18 µm CMOS technology. Because the dead time of SPAD with passive quenching circuit is too long, the main target of the AQC design is to shorten it. On the other hand, the large chip area of AQC will reduce the spatial resolution of the fabricated SPAD array so to minimize the AQC is also important. Our SPADs with well-designed AQC show the fastest dead time of 4 ns, and use the smallest chip area of 15.7×15.2 〖µm〗^2, comparing with others using 0.18 µm CMOS technology. In addition, we demonstrate the function of tunable hold-off time which can be adjusted, according to the characteristics of SPAD, to reduce afterpulsing effect and to lower dark counts. The measured dead time can be extended to more than 280 ns, and the reduced equivalent dark counts are also obtained. Finally, we observe that dark counts and photon detection efficiency (PDE) both increase with increasing excess bias voltages. The highest PDE of 7.5% is achieved. The noise equivalent power (NEP) is about 10-14 WHz-1/2.

碩士
國立交通大學
電子研究所
107
In this work, we realize single photon avalanche diode(SPAD) by using EPISIL 0.8μm CMOS technology. In addition, we implement two SPADs device by using standard CMOS technology which is P+/NWELL SPAD, N+/PWELL SPAD and PWELL/NBL SPAD. Particularly, P+/NWELL SPAD with 27.8V breakdown voltage has a better performance with 10% excess, for example, low dark count rate(DCR) is 56Hz, high photon detect probability(PDP) is 15.38%@495nm, timing jitter FWHM is 157ps. To improve N+/PWELL SPAD and PWELL/NBL SPAD’s characteristics, we introduce the customized CMOS technology for new SPAD(SPAD-A, SPAD-B). From TCAD simulation result, SPAD-A’s breakdown voltage is identical but the depletion width is wider compared with P+/NWELL. The other way, SPAD-B’s breakdown voltage is decreased by using retrograded well. In the end, the customized SPAD’s characteristics are abnormal, whose breakdown voltage is not excepted by simulation. We found out the problem which is the simulation model for ion implant and doping diffuse is not accurate. Although the experiment is not work successfully, it provide the appropriate design flow for future research.

碩士
國立交通大學
電子工程學系 電子研究所
104
In this work, we investigate single-photon avalanche diodes (SPADs) in standard 0.18-m high-voltage CMOS technology provided by TSMC. The SPADs with various kinds of P-N junctions have been designed, fabricated, and characterized. Device simulation and afterward analysis are performed with Sentaurus-TCAD tool. Among the studied devices, 20-m-diameter SPADs formed with deep p-typed well (DPW) and n-typed buried layer (NBL) have the best performance including low dark count rate (DCR), high photon detection efficiency (PDE), low jitter and reduced breakdown voltage comparing with the previous ones in our group. Possible reasons for the improvement are discussed and explained by the simulation on revised doping profiles of the layers. However, the dependence of jitter on the photon wavelength exhibits unusual behavior around 720 nm and calls for further studies in the future.

碩士
國立交通大學
電子研究所
100
In this thesis, by using standard 0.18μm CMOS process, we study the vertical and lateral single-photon avalanche diodes (SPADs). Simulation results show that the lower p-typed and n-typed doping concentration in lateral SPADs can reduce the band-to-band tunneling rate so as their dark count rate. Fifteen devices are fabricated with various parameters such as with/without grating, operation voltages, with/without deep n-well (DNW). The measured breakdown voltages of the vertical and the lateral device are about 10 V and 15 V, respectively, which is consistent with the simulated ones. The characteristics of the SPADs biased below and above the breakdown voltages are measured and discussed. The lateral structure has a higher responsivity and fast transient time, comparing with the vertical structure. It is also found that the grating above the device shows no improvement on its responsivity. For the devices performance above breakdown voltages, different from the simulation results, the dark count rate of the lateral structures is much higher than that of the vertical ones. We suspect that much higher dark count rates are caused by the unwanted shallow trench isolation (STI) in the active region, whose existence is observed with optical and secondary electron microscope. By using gated-mode measurement, we have obtained the de-trapping times of the STI-induced traps under various exceed biases. The dark count rates, photon detection efficiency (PDE) and noise equivalent power (NEP) at 400 nm are measured with long enough dead time to avoid afterpulsing effect.

碩士
國立交通大學
電子工程學系 電子研究所
103
An active reset circuit with excess bias voltage tracking capability for single-photon avalanche diode (SPAD) achieving uniform dark count rate (DCR) and photon detection efficiency (PDE) has been presented. By using sample-and-hold circuit to detect the quenching voltage level of SPAD, the circuit adjusts the reset voltage level of SPAD and keeps the device at constant excess bias voltage of 1.6V. The circuit can compensate the variation of breakdown voltage and biasing voltage up to a range beyond 1V and achieve uniform DCR and PDE within this interval. The chip is fabricated in standard 0.18 m CMOS technology and operates under 3.3V supply voltage. This thesis also demonstrates a time-of-flight (TOF) rangefinding system operating by detecting the phase difference of light pulse. The system consists of SPAD circuits in this thesis as detector, a laser source modulated by pulse train and a gated-mode photon counter implemented by FPGA. The system is verified through introducing different time delay by varying the length of coaxial cable.

碩士
國立交通大學
電子研究所
101
In this thesis, we propose and demonstrate a device structure of low dark-count-rate (DCR) single photon detector. To avoid the breakdown events triggered by the trap of shallow trench isolation (STI) in the active region, we design a guard-ring structure to keep the STI in distance or relocate the active region from the top region to the deeper one. TCAD simulation tool is used to calculate the spatial distributions of electric field and impact ionization to confirm the feasibility of our design. With the 0.25-µm high-voltage standard CMOS technology, we have fabricated the designed devices successfully. The DCRs of devices under various excess voltages have been characterized with the setup in our lab and with the passive quenching circuit. The results show that the DCR of designed structure is lowered by more than two orders comparing with that of the conventional one. The lowest DCR less than 10 Hz is obtained. With a precise calibration of incident power, we have also measured the photon detection efficiency (PDE) of the devices under various excess voltage and incident wavelengths. The highest PDE reaches 15.4 % at 650 nm. At last, we discuss the DCR mechanism of the best device and suggest the direction for further improvement in the future.

碩士
國立交通大學
電子研究所
107
We demonstrate two simple designs to enhance the dynamic ranges for CMOS single-photon avalanche diodes. The one is the time gated active reset scheme, it can be reset by clock signal. The dynamic range of time gated active reset is the best, which the maximum count rate is 225 MHz, it can lift six times the maximum count rate with it closed to the area of the conventional passive reset scheme, and it is the highest SPAD count rate to the best of the author’s knowledge. The other is mutual reset scheme, the system can be quickly reset by SPADs’ mutual effect. It has the ability to dynamically adjust the reset frequency with the intensity of the background light. Under the same conditions, the intervention of mutual reset can enhance about twice the dynamic range. In the ranging histogram, it has no obvious peak of afterpulsing, the afterpulsing probability of mutual reset is 1-3 %, it can reduce misjudgment of mult-echo. Furthermore, we make 4×4 SPAD arrays by time gated active reset and mutual reset schematic, which can be measurement laser under the SPADs’ background count rate of 1 GHz. In this work, we will analyze the dynamic range, ranging experiment, afterpulsing, crosstalk, power, etc. for these systems, and comprehensively analyze their advantages and disadvantages.