Image capture using integrated 3D SoftChip technology

Mobile multimedia communication has rapidly become a significant area of research and development. The processing requirements for the capture, conversion, compression, decompression, enhancement, display, etc. of high quality multimedia content places heavy demands even on current ULSI (ultra large scale integration) systems, particularly for mobile applications where area and power are primary considerations. The system presented is designed as a vertically integrated (3D) system comprising two distinct layers bonded together using indium bump technology. The top layer is a CMOS imaging array containing analog-to-digital converters, and a buffer memory. The bottom layer takes the form of a configurable array processor (CAP), a highly parallel array of soft programmable processors capable of carrying out complex processing tasks directly on data stored in the top plane. Until recently, the dominant format of data in imaging devices has been analog. The analog photocurrent or sampled voltage is transferred to the ADC via a column or a column/row bus. In the proposed system, an array of analog-to-digital converters is distributed, so that a one-bit cell is associated with one sensor. The analog-to-digital converters are algorithmic current-mode converters. Eight such cells are cascaded to form an 8-bit converter. Additionally, each photosensor is equipped with a current memory cell, and multiple conversions are performed with scaled values of the photocurrent for colour processing

Polarization Imaging Sensors in Advanced Feature CMOS Technologies

The scaling of CMOS technology, as predicted by Moore\u27s law, has allowed for realization of high resolution imaging sensors and for the emergence of multi-mega-pixel imagers. Designing imaging sensors in advanced feature technologies poses many challenges especially since transistor models do not accurately portray their performance in these technologies. Furthermore, transistors fabricated in advanced feature technologies operate in a non-conventional mode known as velocity saturation. Traditionally, analog designers have been discouraged from designing circuits in this mode of operation due to the low gain properties in single transistor amplifiers. Nevertheless, velocity saturation will become even more prominent mode of operation as transistors continue to shrink and warrants careful design of circuits that can exploit this mode of operation. In this research endeavor, I have utilized velocity saturation mode of operation in order to realize low noise imaging sensors. These imaging sensors incorporate low noise analog circuits at the focal plane in order to improve the signal to noise ratio and are fabricated in 0.18 micron technology. Furthermore, I have explored nanofabrication techniques for realizing metallic nanowires acting as polarization filters. These nanoscopic metallic wires are deposited on the surface of the CMOS imaging sensor in order to add polarization sensitivity to the CMOS imaging sensor. This hybrid sensor will serve as a test bed for exploring the next generation of low noise and highly sensitive polarization imaging sensors

Realization of low power, highly linear roic with current mode TDI for long wave infrared detectors

Infrared (IR) imaging systems can be used for variety of civil and military applications such as medical imaging, surveillance, night vision and astronomy applications. In IR systems, readout electronic is a key element between detector and signal processing units. System performance parameters of readout electronic can be enumerated as follows: signal-to-noise ratio (SNR), linearity, input referred noise level and dynamic range. In this thesis, design of a CMOS readout integrated circuit (ROIC) for an array of 6x7 as a part of 576x7 full ROIC system, p-on-n type mercury cadmium telluride (HgCdTe) long wave infrared (LWIR) detectors is presented. AMS 0.35 μ[micro]m, 4-metal 2-poly CMOS process is used in the design of ROIC. Preamplifier of ROIC is direct injection(DI) type due to noise performance. In order to increase SNR, time delay integration (TDI) on 7 detectors is applied with a supersampling rate of three. TDI stage implemented as current mode with current memories rather than capacitances to store integrated charges. This particular novel current mode TDI design in this thesis brings superior features over other topologies like high linearity, low area and very low power consumption in comparison with capacitor based topologies. 99.9% linearity is achieved with 2.5 times smaller area with very low power consumption (28 μ[micro]W per channel) compared to other topologies. ROIC has additional features of bidirectional TDI scanning, programmable five gain settings, and programmable integration time by serial/parallel interface. ROIC operated at 1 MHz with an output dynamic range of 3.75V and input referred noise of 1000 rms electrons

Electrochemical Sensors and On-chip Optical Sensors

abstract: The microelectronics technology has seen a tremendous growth over the past sixty years. The advancements in microelectronics, which shows the capability of yielding highly reliable and reproducible structures, have made the mass production of integrated electronic components feasible. Miniaturized, low-cost, and accurate sensors became available due to the rise of the microelectronics industry. A variety of sensors are being used extensively in many portable applications. These sensors are promising not only in research area but also in daily routine applications. However, many sensing systems are relatively bulky, complicated, and expensive and main advantages of new sensors do not play an important role in practical applications. Many challenges arise due to intricacies for sensor packaging, especially operation in a solution environment. Additional problems emerge when interfacing sensors with external off-chip components. A large amount of research in the field of sensors has been focused on how to improve the system integration. This work presents new methods for the design, fabrication, and integration of sensor systems. This thesis addresses these challenges, for example, interfacing microelectronic system to a liquid environment and developing a new technique for impedimetric measurement. This work also shows a new design for on-chip optical sensor without any other extra components or post-processing.Dissertation/ThesisDoctoral Dissertation Electrical Engineering 201

A low-noise microluminometer for a bioluminescent bioreporter integrated circuit

This thesis presents the analysis and design of a low-noise microluminometer for a hybrid electronic/biological chemical sensor known as a Bioluminescent Bioreporter Integrated Circuit (BBIC). The microluminometer consists of photodetection and signal processing Both functions are integrated in a standard bulk CMOS process (HP 0.5 urn CMOS). The photodetection is first described in terms of physical operation. The implementation of photodetectors in a CMOS integrated circuit process is then presented. The signal processing system is analyzed, and the errors introduced by individual system components are described. A detailed system-level noise analysis is also presented The design of a low-noise amplifier is the focus of this thesis. The amplifier design is described in detail. Finally, the results from testing of the fabricated prototype are presented

Optical microsystem for spectroscopy signals extraction applied to gastrointestinal dysplasia detection

Tese de Doutoramento em Engenharia BiomédicaThe early detection of gastrointestinal cancer, in the dysplastic stage, is essential to increase the patient survival rate. Spectroscopic techniques, particularly diffuse reflectance and fluorescence, can improve the gastrointestinal dysplasia detection, since these techniques can be used to extract biochemical and morphologic information related with the status of a gastrointestinal tissue. Several research groups have developed prototypes for the extraction of diffuse reflectance and fluorescence signals applied to gastrointestinal cancer detection. Despite their advantages associated with the gastrointestinal cancer identification, they have several disadvantages related with the use of complex, high-cost and sophisticate components such as xenon lamps, lasers, monochromators, optical fibers and high quantum efficiency detectors, which may hamper their wide use as well as their huge clinical value. Therefore, it is of utmost importance to develop a low-cost, miniaturized and minimal invasive microsystem for spectroscopic signals extraction. As a result, in this work it is proposed the implementation of a microsystem, which comprises in a single chip, an optical filter system for selection and extraction of the diffuse reflectance and fluorescence signals in relevant spectral bands, a silicon photodiodes matrix (4×4) and its readout electronics, and miniaturized light emitting diodes. The main applications of this microsystem are: its use as a portable device in a surgery room for inspection of total removing of the cancerous or dysplastic tissue; and its integration with the standard endoscopes and colonoscopes using it as an auxiliary, to the physician, in early gastrointestinal cancer detection. Along this thesis, important steps towards that microsystem implementation were achieved. In a first step experimental measurements were performed, with phantoms representative of the main absorbing, scattering and fluorescence properties of gastrointestinal tissues (containing hemoglobin, polystyrene microspheres to represent collagen fibers, and the fluorophores NADH and Carbostyril 124, the latter representing collagen), in order to study the diffuse reflectance and fluorescence typical spectra and their temperature dependence. Moreover, the viability of using only 16 spectral bands (between 350 and 750 nm) for signals extraction was discussed, proving the feasibility of an optical filter system implementation in the final microsystem. Therefore, it were designed, fabricated and characterized 16 MgO/TiO2 and SiO2/TiO2 based thin-film optical filters. Their characterization performed through optical transmittance, selectivity, profilometry and scanning electron microscopy, allowed understanding the deviations between the simulated characteristics and the ones experimentally obtained. Moreover, the optical filters results showed transmittances ranging from 50% to 90% approximately, and a full width half maximum (FWHM) averaging from 11 nm to 20 nm, which fits the required application. The fabricated optical filters had some deviations considering their simulated characteristics, which can be explained by the complexity of the optical filters design, for example, the materials refractive index dependence with wavelength and thin-film thickness. The diffuse reflectance and fluorescence signals that pass through the optical filters can be measured with an on-chip silicon photodetectors matrix (4×4), based on n+/p-epilayer junction photodiodes with an active area of 100 × 100 µm2, and a light-to-frequency converter, per each photodiode, that enables producing a digital signal with a frequency proportional to the photodiode current. As a result, the design and implementation of a CMOS microsystem comprising these components were performed. The photodiodes characterization showed a responsivity of 200 mA/W at 550 nm, approximately, and the light-to-frequency converter connected to the photodiode showed a linear response (R2>0.99) with a sensitivity of 25 Hz/nA at 550 nm, approximately. The behavior of the current-to-frequency converter, with an external current source directly injected in its input, was also studied allowing to confirm its linearity in the range of currents produced in this application, its power consumption of 1 mW, and its maximum input current, approximately 300 µA. This CMOS approach avoids the need of an expensive readout optical microsystem, since it is possible to integrate the photodiodes and the readout electronics in a small silicon area (275 × 100 µm2 per photodiode and its respective converter). The performance of the implemented microsystem and the fabricated optical filters was evaluated, using phantoms (also containing hemoglobin, polystyrene microspheres, NADH and Carbostyril 124). The obtained results have shown the viability of the microsystem (including the optical filter system) to extract diffuse reflectance and fluorescence signals. Some issues were noted on the sensitivity of the implemented optical setups for the on-chip measurements. However, some solutions were proposed for the remaining problems, specifically the future use of miniaturized light emitting diodes and the direct deposition of the optical filters on the top of the photodetection system. Finally, the direct integration of optical filters on top of the photodiodes was discussed and a new approach was tested.The author, Sara Filomena Ribeiro Pimenta, was supported by the Portuguese Foundation for Science and Technology (in portuguese FCT – Fundação para a Ciência e a Tecnologia) with the PhD grant SFRH/BD/87605/2012. This work is also funded by FEDER funds through the “Eixo I do Programa Operacional Fatores de Competitividade” (POFC) QREN, project reference COMPETE: FCOMP-01-0124-FEDER- 020241 and by FCT, project reference PTDC/EBB-EBI/120334/2010. Finally, the author thanks to the PEst-C/FIS/UI0607/2013, UID/FIS/04650/2013, UID/EEA/04436/2013 and POCI-01- 0145-FEDER-006941 for the use of equipment.A deteção precoce do cancro gastrointestinal, na fase de displasia, é essencial para o aumento da taxa de sobrevivência do paciente. As técnicas de espetroscopia, particularmente a refletância difusa e a fluorescência, permitem melhorar a deteção de displasia gastrointestinal, ao poderem ser utilizadas para a extração de informação bioquímica e morfológica associada ao estado do tecido gastrointestinal. Diversos grupos de investigação têm desenvolvido protótipos para a extração de sinais de refletância difusa e de fluorescência, para aplicação na deteção do cancro gastrointestinal. Apesar das vantagens associadas com a identificação do cancro gastrointestinal, esses sistemas apresentam várias desvantagens relacionadas com a utilização de componentes complexos, de elevado custo e sofisticados, como por exemplo, lâmpadas de xénon, lasers, monocromadores, fibras óticas e detetores de elevada eficiência, que podem dificultar a sua ampla utilização, bem como o seu elevado valor clínico. Portanto, é de extrema importância o desenvolvimento de um microssistema de baixo custo, miniaturizado e minimamente invasivo para a extração de sinais de espetroscopia. Assim, neste trabalho é proposta a implementação de um microssistema, num único chip, compreendendo: um sistema de filtros óticos para a seleção dos sinais de refletância difusa e de fluorescência em bandas espetrais relevantes; uma matriz de fotodíodos de silício (4×4) e a respetiva eletrónica de leitura; e díodos emissores de luz miniaturizados. As principais aplicações deste microssistema são: a sua utilização como sistema portátil numa sala de cirurgia para inspeção da remoção total do tecido maligno ou displásico; ou a sua integração com os sistemas de endoscopia e colonoscopia, servindo como auxiliar de diagnóstico, na deteção precoce de cancro gastrointestinal. Com a realização desta tese foram dados passos importantes para a implementação desse microssistema. Numa primeira fase, foram realizados testes experimentais, com um grupo de fantomas representativos das propriedades de absorção, difusão e de fluorescência dos tecidos gastrointestinais (contendo hemoglobina, microesferas de polistireno representando as fibras de colagénio, e os fluoróforos NADH e Carbostyril 124, este último para representar o colagénio), de forma a obter os espetros típicos de refletância difusa e de fluorescência e a influência da temperatura do fantoma nos mesmos. Para além disso, a viabilidade de usar apenas 16 bandas espetrais (entre 350 e 750 nm) para a extração dos sinais espetroscópicos foi discutida, provando a exequibilidade da implementação de um sistema de filtros óticos no microssistema final. Assim, foram desenhados, fabricados e caracterizados 16 filtros óticos baseados em filmes finos de MgO/TiO2 e SiO2/TiO2. A sua caracterização do ponto de vista da transmitância ótica, seletividade, profilometria e microscopia eletrónica de varrimento, permitiu perceber os desvios verificados entre as características simuladas e as obtidas experimentalmente. Para além disso, os resultados da caracterização dos filtros óticos mostraram transmitâncias óticas que variam entre 50% e 90%, aproximadamente, e uma largura a meia-altura (FWHM) média entre 11 nm e 20 nm, o que é adequado para a aplicação pretendida. Os filtros óticos fabricados possuem alguns desvios das suas características simuladas, o que pode ser explicado pela complexidade no projeto de filtros óticos, por exemplo, a dependência dos índices de refração com o comprimento de onda e espessura do filme fino. Os sinais de refletância difusa e fluorescência que atravessam os filtros óticos podem ser medidos através de uma matriz de fotodetetores de silício (4×4), baseada em fotodíodos do tipo n+/p-epilayer com uma área ativa de 100 × 100 µm2, e um conversor luz-frequência, um por cada fotodíodo, que permite produzir um sinal digital com uma frequência proporcional à corrente gerada pelo fotodíodo. Assim, o projeto e a implementação de um microssistema CMOS incluindo esses componentes foram executados. A caracterização dos fotodíodos da matriz resultou num valor de responsividade de 200 mA/W a 550 nm, aproximadamente, e a do conversor luz-frequência, quando ligado a um fotodíodo, resultou numa resposta linear (R2>0.99) com uma sensibilidade de 25 Hz/nA a 550 nm, aproximadamente. O comportamento do conversor corrente-frequência, com uma fonte de corrente externa diretamente injetada na sua entrada, foi também estudado, permitindo confirmar a sua linearidade na gama de correntes envolvidas nesta aplicação, a sua potência de consumo de 1 mW, e a sua corrente de entrada máxima, aproximadamente 300 µA. Esta abordagem em tecnologia CMOS evita a utilização de um microssistema ótico de leitura de elevado custo, uma vez que torna possível a integração dos fotodíodos e respetiva eletrónica de leitura numa área de silício pequena (275 × 100 µm2 por fotodíodo e respetivo conversor). Foi avaliado o desempenho do microssistema implementado e dos filtros óticos fabricados usando fantomas (mais uma vez contendo hemoglobina, microesferas de polistireno, NADH e Carbostyril 124). Os resultados obtidos provaram a viabilidade do microssistema (incluindo o sistema de filtros óticos) para a extração de sinais de refletância difusa e de fluorescência. Foram notados alguns problemas na sensibilidade dos setups óticos implementados para as medições on-chip. No entanto, foram também propostas algumas soluções para os respetivos problemas, especificamente o uso futuro de díodos emissores de luz miniaturizados e a deposição direta dos filtros óticos no sistema de fotodeteção. Finalmente, a integração dos filtros óticos depositados diretamente em cima dos fotodíodos foi discutida e uma nova abordagem foi testada

70 Gb/s low-power DC-coupled NRZ differential electro-absorption modulator driver in 55 nm SiGe BiCMOS

We present a 70 Gb/s capable optical transmitter consisting of a 50 mu m long GeSi electro-absorption modulator (integrated in silicon photonics) and a fully differential driver designed in a 55 nm SiGe BiCMOS technology. By properly unbalancing the output stage, the driver can be dc-coupled to the modulator thus avoiding the use of on-chip or external bias-Ts. At a wavelength of 1560 nm, open eye diagrams for 70 Gb/s after transmission over 2 km standard single-mode fiber were demonstrated. The total power consumption is 61 mW, corresponding to 0.87 pJ/b at 70 Gb/s. Bit-error rate measurements at 50 Gb/s and 56 Gb/s (performed both back to back and with up to 2 km standard single-mode fiber) demonstrate large (0.4 UI at a BER of 10(-12)) horizontal eye margins. This optical transmitter is ideally suited for datacenter applications that require densely integrated transceivers with a low power consumption

A low-voltage CMOS-compatible time-domain photodetector, device & front end electronics

During the last decades, the usage of silicon photodetectors, both as stand-alone sensor or integrated in arrays, grew tremendously. They are now found in almost any application and any market range, from leisure products to high-end scientific apparatuses, including, among others, industrial, automotive, and medical equipment. The impressive growth in photodetector applications is closely linked to the development of CMOS technology, which now offers inexpensive and efficient analog and digi-tal signal processing capabilities. Detectors are often integrated with their respective front end and application-specific digital circuit on the same silicon die, forming complete systems on chip. In some cases the detector itself is not on the same chip but often part of the same package. However, this trend of co-integration of analog front end and digital circuits complicates the design of the analog part. The ever-decreasing supply voltage and the smaller transistors in advanced processes (which are driven by the development of digital cir-cuits) negatively impact the performance of the analog structures and complicates their design. For photodetector systems, the effect most importantly translates into a degradation of dynamic range and signal-to-noise ratio. One way to circumvent the problem of low supply voltages is to shift the operation from voltage domain to time domain. By doing so, the signal is no longer constrained by the supply rails and analog amplification is avoided. The signal takes the form of a time-based modulation, such as pulse-width modulation or pulse-frequency modulation. Another advantage is that the output signal of a time-domain photodetection system is directly interfaceable with digital circuits. In this work, a new type of CMOS-compatible photodetector displaying intrinsic light-to-time conversion is proposed. Its physical structure consists of a MOS gate interleaved with a PN junction. The MOS structure is acting as a photogate. The depletion region shrinks when photogenerated carriers fill the potential well. At some point, the anode of the PN structure is de-isolated from the rest of the detector and triggers a positive-feedback effect that leads to a very steep current increase through the PN-junction. This translates into a signal of very high amplitude and independent from light-intensity, which can be almost directly interfaced with digital circuits. This simplifies the front end circuit compared to photodiode-based systems. The physical behavior of the device is analyzed with the help of TCAD simulations and simple behavioral and shot-noise models are proposed. The device has been co-integrated with its driver and front end circuit in a standard CMOS process and its characteristics have been measured with a custom-made measurement system. The effect of bias parameters on the performance of the sensor are also analyzed. The limitations of the device are discussed, the most important ones being dark current and linearity. Techno-logical solutions, such as the implementation of the detector on Silicon-on-Insulator technology, are proposed to overcome the limitations. Finally, some application demonstrators have been realized. Other applications that could benefit from the detector are suggested, such as digital applications taking advantage of the latching behavior of the device, and a Photoplethysmography (PPG) system that uses a PLL-based control loop to minimize the emitting LED-current

Low-power CMOS circuit design for fast infrared imagers

La present tesi de màster detalla novedoses tècniques circuitals per al disseny de circuits integrats digitals CMOS de lectura compactes, de baixa potència i completament programables, destinats a aplicacions d'IR d'alta velocitat operant a temperatura ambient. En aquest sentit, el treball recull i amplia notablement la recerca iniciada en el Projecte Final de Carrera "Tècniques de disseny CMOS per a sistemes de visió híbrids de pla focal modular" obtenint-se resultats específics en tres diferents àrees: Recerca de l'arquitectura òptima d'FPA, des del punt de vista funcional i de construcció física. Disseny d'un conjunt complet de blocs bàsics d'autopolarització, compensació de la capacitat d'entrada i del corrent d'obscuritat, conversió A/D i interfície d'E/S exclusivament digital, amb compensació de l'FPN. Aplicació industrial real: Integraciió de tres versions diferents de píxel per sensors PbSe d'IR i fabricació de mòduls ROIC monolítics i híbrids en tecnologia CMOS estàndard 0.35&·956;m 2-PoliSi4-metall. Caracterització elèctrica i òptica-preliminar de les llibreries de disseny