Research Interests: Computer Science, Materials Science, Raman Spectroscopy, Nanostructured materials, Photoluminescence, and 15 moreOptoelectronics, Chemical Vapor Deposition, Band Gap, Luminescence, Optical Properties, Sapphire, Optical band gap, Scattering, Nanocrystals, Nanostructured Material, Origin, Emission, Experimental Data, Layers, and photoluminiscence
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Research Interests: Physics and Humanities
This article presents a complete design flow of a low noise transimpedance amplifier for 10 Gbps optoelectronic receivers. The proposed topology is based on the shunt-shunt structure with negative feedback. A set of equations was... more
This article presents a complete design flow of a low noise transimpedance amplifier for 10 Gbps optoelectronic receivers. The proposed topology is based on the shunt-shunt structure with negative feedback. A set of equations was deduced from the frequency analysis and noise analysis. An optimization algorithm is proposed in order to maximize the bandwidth and improve the noise performance simultaneously. Experimental results shown a 51 dBΩ transimpedance gain, a 10.54 Ghz bandwidth and an input referred current noise equal to 6.8, the lowest one between other state-of-art designs. The circuit was manufactured in 130 nm RF CMOS technology.
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INVESTIGAMOS EL GRABADO IONICO REACTIVO DE SILICIO USANDO PLASMAS CON MEZCLAS DE GASES QUE CONTIENEN FLUOR SF6/CH4(CF4)/O2/AR PARA SU APLICACION EN MICROSISTEMAS ELECTROMECANICOS. EXAMINAMOS LA VELOCIDAD DE GRABADO Y LA ANISOTROPIA DEL... more
INVESTIGAMOS EL GRABADO IONICO REACTIVO DE SILICIO USANDO PLASMAS CON MEZCLAS DE GASES QUE CONTIENEN FLUOR SF6/CH4(CF4)/O2/AR PARA SU APLICACION EN MICROSISTEMAS ELECTROMECANICOS. EXAMINAMOS LA VELOCIDAD DE GRABADO Y LA ANISOTROPIA DEL PERFIL EN FUNCION DE LA COMPOSICION DEL GAS, DEL MATERIAL DEL ELECTRODO Y DE LA POTENCIA DE RADIO FRECUENCIA. LA PROFUNDIDAD DE GRABADO SE DETERMINA USANDO UN PERFILOMETRO Y LOS PERFILES GRABADOS SE ANALIZAN MEDIANTE UN MICROSCOPIO ELECTRONICO DE BARRIDO. COMO MATERIAL ENMASCARANTE, USAMOS UNA PELICULA DE ALUMINIO DEPOSITADA POR EVAPORACION. OBTUVIMOS UNA ALTA ANISOTROPIA DE GRABADO DE 0.95 CON PROFUNDIDADES DE 20 A 30 MICRAS Y VELOCIDADES DE GRABADO DE APROXIMADAMENTE 0.3 A 0.66 µM/MIN. EL GRABADO ALTAMENTE ANISOTROPO SE BASA EN UN MECANISMO QUE AUMENTA EL BOMBARDEO DE IONES Y PROTEGE LAS PAREDES POR POLIMERIZACION Y/U OXIDACION PARA EVITAR EL GRABADO LATERAL. SIN EMBARGO, BAJO CONDICIONES DE GRABADO ANISOTROPO SE OBSERVARON CONSIDERABLES DANOS EN LA...
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Silicon oxynitride (SiO x N y ) insulators have been grown using O 2 /N 2 /Ar gas mixtures at room temperature (20°C), in a wide pressure range (5, 10, 20 and 50mTorr) and 1000 W microwave power electron cyclotron resonance (ECR) plasma... more
Silicon oxynitride (SiO x N y ) insulators have been grown using O 2 /N 2 /Ar gas mixtures at room temperature (20°C), in a wide pressure range (5, 10, 20 and 50mTorr) and 1000 W microwave power electron cyclotron resonance (ECR) plasma on Si substrates. The thickness values between 1.8 nm and 6.3 nm were determined by ellipsometry. Fourier transform infra-red (FTIR) spectrometry analyses reveal the chemical bonds in the silicon oxynitride films, indicating that the oxynitrides grown at medium pressures, between 10 and 20 mTorr, presented less nitrogen content than those grown at 5 and 50 mTorr. Optical emission spectroscopy (OES) was used for plasma characterization, and intense formation of NO molecules in the gas phase was detected. These molecules can play significant role in formation of the oxynitride layer and the resulting N/O ratio in the surface layer. The C-V characteristics of Al/Ti/SiO x N y /Si specimens were obtained and the EOT (equivalent oxide thickness) values wer...
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A set of low noise transimpedance amplifiers manufactured and characterized in CMOS and BiCMOS technologies is proposed in this work. Layout optimization, efficient modelling and bias point optimization are the techniques employed to... more
A set of low noise transimpedance amplifiers manufactured and characterized in CMOS and BiCMOS technologies is proposed in this work. Layout optimization, efficient modelling and bias point optimization are the techniques employed to reduce the input noise current density. The CMOS amplifiers were designed to work at 10 Gbps. The BiCMOS amplifiers, based on HBT transistors, can operate at bit rates higher than 25 Gbps. To the best of our knowledge, the broadband amplifiers proposed in this work have the lowest input noise current density compared to other 0.13 μm designs.
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ABSTRACT Carbon nanotubes (CNTs) have attracted much attention due to their extraordinary properties. This nanostructured material has been synthesized by various methods and the chemical vapor deposition (CVD) has been shown to be an... more
ABSTRACT Carbon nanotubes (CNTs) have attracted much attention due to their extraordinary properties. This nanostructured material has been synthesized by various methods and the chemical vapor deposition (CVD) has been shown to be an efficient and versatile technique. In this work, catalytic thermal CVD method, using a mixture of methane and hydrogen at atmospheric pressure on a horizontal tubular quartz furnace, was used to grow carbon nanotubes. Silicon wafers with SiO2 or Al2O3 layers were used as substrates whereas thin nickel film was deposited over the substrates and used as catalyst. The interaction between catalyst nickel film and two different oxide layers supported on silicon wafers was studied as well as the influence of both substrates (Si/SiO2 and Si/Al2O3) on the carbon nanotube growth. It was observed a completely different interaction between Ni film and both oxide layers, affecting strongly the growth of CNTs.
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This work presents a device for pH measurements called Electrolyte-Insulator-Semiconductor (EIS), which operates as a Metal-Oxide-Semiconductor capacitor but instead of having the metal contact electrode, an electrolyte solution and a... more
This work presents a device for pH measurements called Electrolyte-Insulator-Semiconductor (EIS), which operates as a Metal-Oxide-Semiconductor capacitor but instead of having the metal contact electrode, an electrolyte solution and a reference electrode are used to apply voltage. It was used TiO2 thin film as insulator and sensitive membrane. These films were obtained after rapid thermal oxidation of Ti thin films deposited by sputtering. They were structurally characterized by Raman and ellipsometry which reveal that the films present rutile crystal structure. We use capacitors to make the electrical characterization of TiO2 films in order to determine the annealing time that leads to the best thin film properties, defined by high dielectric constant value (high-k), lower charge density (Q0/q) and flat-band voltage (VFB) around -0.9V. EIS devices are tested through capacitance x voltage (CxV) measurements using different pH solutions. When in contact to the dielectric film, each pH value adds a contribution to the flat band voltage, resulting in a displacement of the CxV curve. It was possible to determine from the flat band voltage (VFB), the sensitivity of 41 mV/pH.
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Research Interests: Materials Science, Raman Spectroscopy, Titanium, Atomic Force Microscopy, Thin Film, and 14 moreDIELECTRIC, Leakage Current, Refractive Index, Grain size, Anatase, Silicon Wafer, Dielectric Constant, Fourier transform infrared spectroscopy, Titanium oxide, Charge Density, Rutherford Backscattering Spectroscopy, Electrical And Electronic Engineering, Field effect transistor, and Rough Surface
Research Interests: Materials Engineering, Aerospace Engineering, Materials Science, Optoelectronics, Chemical Vapor Deposition, and 12 moreAtmospheric sciences, Silicon Nitride, Layer, Nitride, Bipolar transistors, Vacuum Science and Technology, Passivation, BASE, GaAs, Heterojunction, Device degradation, and Electron Cyclotron Resonance Heating
ABSTRACT The silicon-based gate-controlled lateral bipolar junction transistor (BJT) is a controllable four-terminal photodetector with very high responsivity at low-light intensities. It is a hybrid device composed of a MOSFET, a lateral... more
ABSTRACT The silicon-based gate-controlled lateral bipolar junction transistor (BJT) is a controllable four-terminal photodetector with very high responsivity at low-light intensities. It is a hybrid device composed of a MOSFET, a lateral BJT, and a vertical BJT. Using sufficient gate bias to operate the MOS transistor in inversion mode, the photodetector allows for increasing the photocurrent gain by $10^{6}$ at low light intensities when the base-emitter voltage is smaller than 0.4 V, and BJT is off. Two operation modes, with constant voltage bias between gate and emitter/source terminals and between gate and base/body terminals, allow for tuning the photoresponse from sublinear to slightly above linear, satisfying the application requirements for wide dynamic range, high-contrast, or linear imaging. MOSFETs from a standard 0.18-$mu{rm m}$ triple-well complementary-metal oxide semiconductor technology with a width to length ratio of 8 $mu{rm m}$/2 $mu{rm m}$ and a total area of ${sim}{rm 500}~mu{rm m}^{2}$ are used. When using this area, the responsivities are 16–20 kA/W.
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Stimulation and recording of nerve cells is a procedure used for several applications, such as clinical therapies, study of basic neuroscience, and neural prostheses. Microtechnology and advances in material science have allowed to... more
Stimulation and recording of nerve cells is a procedure used for several applications, such as clinical therapies, study of basic neuroscience, and neural prostheses. Microtechnology and advances in material science have allowed to produce more sophisticated devices and with more functions. This paper focuses on the fabrication of planar 60 – channel Microelectrode Arrays (MEAs). The electrical characterization of the noise level from the TiN electrodes showed good sensitivity to noise, compatible with commercial systems. These electrodes received an artificial electrocardiogram signal (ECG) from a function generator and registered the same input signal but with lower amplitude. Finally, both cyclic voltammetry curves of the produced MEA and the commercial MEA exhibited similar shape, but the current density of the first one was significantly higher than in MCS – MEA, with an order difference of magnitude.
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Este trabalho de dissertacao apresenta o estudo e projeto dos elementos que compoem um sensor de gases baseado na tecnologia de Onda Acustica de Superficie (SAW), tais como, o oscilador colpitts SAW e um ressonador SAW de uma porta, os... more
Este trabalho de dissertacao apresenta o estudo e projeto dos elementos que compoem um sensor de gases baseado na tecnologia de Onda Acustica de Superficie (SAW), tais como, o oscilador colpitts SAW e um ressonador SAW de uma porta, os quais estao na malha de realimentacao de um amplificador. Foi realizado tambem a deposicao de diferentes espessuras de filme fino de TiO2 sobre o sensor, a fim de se estudar o efeito da atenuacao da SAW na fronteira entre o cristal e o filme. E mostrado que atenuacao da SAW acontece no filme na fina camada de aproximadamente 500 angstroms de espessura. A dependencia de espessura com a mudanca de frequencia e com fator Q do oscilador SAW e ressonador sao apresentados, bem como a ssensitividade de massa do ressonador SAW para o filme de TiO2. Um modelo de oscilador SAW usando 2 caminhos acusticos, de melhor sensitividade que aquele de modo simples, foi estudado e proposto. Abstract
Research Interests: Physics and Humanities
Foi estabelecido um processo para a fabricacao em laboratorio de Transistores Bipolares de Heterojuncao (HBTs), em AIGaAs/GaAs. O trabalho consistiu basicamente do estudo das etapas elementares de fabricacao. Foi projetado um conjunto de... more
Foi estabelecido um processo para a fabricacao em laboratorio de Transistores Bipolares de Heterojuncao (HBTs), em AIGaAs/GaAs. O trabalho consistiu basicamente do estudo das etapas elementares de fabricacao. Foi projetado um conjunto de mascaras incluindo dispositivos em diferentes tamanhos e estruturas de teste. Com este conjunto de mascaras, as etapas de processamento de HBTs foram estudadas e transistores HBT foram fabricados. Foi analisado um metodo para se determinar com precisao o ponto de parada de etch umido, consistindo da medida da currente reversa em um diodo Schottky formado entre a superficie semicondutora e uma ponta de tungstenio. Com este metodo foi possivel expor com precisao a camada de base. A abertura de vias de contato em paredes em ângulo controlado foi obtida transferindose o ângulo de inclinacao de uma parede de fotorresiste para a parede da via em polyimide. Estruturas de metal para contatos ohmicos baseadas em AuGe, para contatos n+ e Ti/Pt/ Au, para camad...
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ABSTRACT This paper deals with a very simple technology for fabrication of high performance n-channel Al-gate enhancement load digital integrated circuits. Using a nine-stage ring oscillator with triode load, an intrinsic time delay of... more
ABSTRACT This paper deals with a very simple technology for fabrication of high performance n-channel Al-gate enhancement load digital integrated circuits. Using a nine-stage ring oscillator with triode load, an intrinsic time delay of 1·9 ns and a speed-power product of 1·45 pJ were measured. A two kbit ROM memory with 50 ns access time was designed and fabricated with this technology.
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A new approach to improve the electrical and thermal contacts between multi-walled carbon nanotubes and metallic electrodes was developed by using spatially localized laser heating coupled with a micro Raman equipment. After the... more
A new approach to improve the electrical and thermal contacts between multi-walled carbon nanotubes and metallic electrodes was developed by using spatially localized laser heating coupled with a micro Raman equipment. After the deposition by dielectrophoresis, the nanotubes were heated in ambient atmosphere by a focused laser beam in order to improve the electrical contacts of the nanostructures with different electrodes (W, Ti and Au) and also to excite the Raman signal of the nanotubes. The changes in the vibrational frequencies of the Raman bands of the nanotubes provides a real time feedback of the treatment conditions allowing to estimate the local temperature, which is used for adjusting the parameters of treatment. Laser treatment tests were performed in a single step (single exposition of the sample to laser) or gradually (successive expositions of the sample to laser, with gradual increase of the used laser power density) and better results were obtained for the gradual tr...
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O trabalho apresentado nesta tese endereca dois importantes desafios impostos pela evolucao da tecnologia CMOS, a diminuicao da responsividade das juncoes e a reducao da tensao de alimentacao. Um fotodetector de alta responsividade e um... more
O trabalho apresentado nesta tese endereca dois importantes desafios impostos pela evolucao da tecnologia CMOS, a diminuicao da responsividade das juncoes e a reducao da tensao de alimentacao. Um fotodetector de alta responsividade e um sistema de imagem CMOS multiamostrado no dominio do tempo sao propostos nesta tese. Como fototransistor de elevada responsividade propoem-se nesta tese o uso do Transistor Bipolar Lateral Controlado por Porta (GC-LBJT) operando como fototransistor de 4 terminais. Apresenta-se a analise do principio de funcionamento e o desenvolvimento de um circuito equivalente CC. A fotoresposta do GC-LBJT e investigada em duas diferentes configuracoes, coletor-comum com tensao porta-base constante e emissor-comum com tensao porta-emissor constante. A caracteristica da fotoresposta e associada as equacoes do dispositivo em ambas as configuracoes mostrando os principais parâmetros do dispositivo que determinam o ganho. Na configuracao coletor-comum, a caracteristica da fotoresposta varia de aproximadamente linear a sublinear por meio da tensao de controle VGB. Na configuracao emissor-comum, o dispositivo apresenta fotoresposta sublinear e baixa excursao para toda faixa de tensao de controle (VGB) utilizada. Explorando a caracteristica controlavel do GC-LBJT em ambas as configuracoes, o fototransistor GC-LBJT pode apresentar ganho e responsividade maiores do que 10+6 e 10+4 A/W respectivamente. Propoe-se o metodo de multipla-amostragem para sistemas de imagem CMOS no dominio do tempo. O pixel e composto por um comparador e um circuito de memoria de um bit. O metodo de multipla-amostragem no dominio do tempo permite reduzir o circuito de memoria integrado ao pixel de 8 bits tipicamente para um unico bit. O resultado da amostra armazenado na memoria de um bit no pixel e lida externamente de forma sincrona e o valor do sinal do pixel e codificado de acordo com o instante da amostra no tempo. O numero de bits e a velocidade de operacao do circuito limitam a dimensao maxima da matriz. Alem disso, este trabalho apresenta a influencia da nao-linearidade da capacitância do fotodiodo na caracteristica da fotoresposta dos sistemas de imagem CMOS no dominio do tempo. Estudo do comportamento do ruido de padrao fixo e o temporal em sistema de imagem no dominio do tempo tambem sao apresentados Abstract
Research Interests: Physics and Humanities
Este trabalho nasceu da necessidade de melhorar a qualidade e confiabilidade de produtos fabricados. Para atingir este objetivo, o passo mais importante e a de qualificar os componentes que sao usados nestes produtos. Neste trabalho... more
Este trabalho nasceu da necessidade de melhorar a qualidade e confiabilidade de produtos fabricados. Para atingir este objetivo, o passo mais importante e a de qualificar os componentes que sao usados nestes produtos. Neste trabalho apresentaremos uma Metodologia de Qualificacao de componentes Eletronicos, onde abordaremos todos os passos necessarios para mostrar que os componentes tenham um nivel de qualidade e confiabilidade compativeis com os requisitos exigidos por um fabricante de equipamentos eletronicos que coloca seus produtos no mercado. A confiabilidade de um produto pode ser medida pelo seu Tempo Medio Entre Falhas (MTBF), normalmente corresponde a 40.000 horas (para produtos na area de informatica), que e a vida util do produto. Para se atingir este objetivo e necessario que os componentes tenham um nivel de confiabilidade muito alto. Este nivel pode ser medido pela sua Taxa de Falha Media, que e a porcentagem de falha em um determinado periodo de tempo. Apresentaremos a metodologia de qualificacao descrevendo os principais tipos de testes que os componentes sao submetidos e a teoria estatistica com os modelos matematicos de fatores de aceleracao e calculo do numero de amostras e da taxa de falha media apos os testes de confiabilidade. Vale lembrar que toda a teoria estatistica aqui apresentada e baseada em metodos empiricos, atraves de experiencias que os fabricantes e centros de pesquisa executaram durante anos e que condensaram os resultados para se criar esta teoria. Veremos tres estudos de caso para exemplificar toda a metodologia de qualificacao. Inicialmente, apresentaremos resultado da qualificacao de Diodos Emissores de Luz (LED), neste exemplo apresentaremos todos os passos necessarios para a qualificacao e seus resultados. Veremos resultados de dois testes criticos para este tipo de tecnologia, ou seja, a Analise de Construcao, onde observamos alguns problemas relacionados com o processo de encapsulamento e o teste de Degradacao Luminosa, onde observamos uma degradacao (perda de luminosidade) de ate 31% durante o teste de alta temperatura. Apresentaremos resultados da qualificacao de Modulos de cristais Liquidos (LCD). Esta tecnologia apresentou excelentes resultados, exceto na Analise de Construcao onde encontramos alguns problemas no processamento da pastilha do Circuito Integrado controlador/driver. Este resultado foi importante porque nos deu um direcionamento de como aplicar um esforco maior durante os testes de confiabilidade na pastilha do Circuito Integrado. No terceiro estudo de caso, apresentaremos resultados da qualificacao de Circuitos Integrados TTL. Os resultados apresentados neste terceiro caso sao muito sucintos, pois todos os passos ja foram apresentados nos casos precedentes, evitando assim redundância na apresentacao dos resultados. Alem disto, esta tecnologia nao apresentou nenhum ponto de preocupacao durante os testes de qualificacao. Os tres casos analisados nao apresentaram problemas relacionados a confiabilidade, porem foram identificados falhas de Controle de Qualidade nas linhas de producao de um fornecedor, tendo sido propostos as melhorias necessarias. Analisamos limitacoes na metodologia de qualificacao de componentes eletronicos, por nao levar em consideracao alguns pontos relevantes que poderiam dar uma maior precisao na previsao da confiabilidade do produto. Como continuidade deste trabalho, sugerimos estudar uma nova metodologia para avaliar a confiabilidade dos componentes Abstract
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Neste trabalho apresentamos um estudo inicial sobre os mecanismos de transporte de corrente envolvidos em uma heterojuncao. Vemos que os mecanismos de deriva e difusao nao sao suficientes para descrever seu comportamento eletrico ( devido... more
Neste trabalho apresentamos um estudo inicial sobre os mecanismos de transporte de corrente envolvidos em uma heterojuncao. Vemos que os mecanismos de deriva e difusao nao sao suficientes para descrever seu comportamento eletrico ( devido a um spike na banda de conducao, no caso de transistor Npn), sendo introduzido o mecanismo de Emissao-Termionica. Considerando este novo mecanismo modelos EBERS-MOLL e GUMMEL-POON sao obtidos para descrever este transistor. Destes modelos, considerando um transistor de uma unica heterojuncao abrupta na juncao de base-emissor, obtemos as equacoes das correntes de base e de coletor na regiao onde os efeitos de resistencias parasitarias e termicos sao desprezados. Nestas condicoes mostramos a equivalencia entre os dois modelos e consideramos somente o modelo EBERS-MOLL. Comparando os resultados praticos com os teoricos, vemos correntes de coletor calculadas muito menores que os valores medidos. Isto se deve ao fato de nao levarmos em conta o tunelamento de cargas atraves do spike. O efeito do tunelamento e aumentar o valor da corrente e saturacao (IS) e o fator de idealidade (nF). Assim conseguimos uma boa concordância entre o modelo teorico e as curvas experimentais. Para altos valores de tensao entre base-emissor, o tunelamento desvia o modelo das curvas experimentais. Tendo o modelo, partimos para a obtencao dos parâmetros necessarios a sua descricao Avaliamos e implementamos um conjunto de tecnicas de medidas e extracao de parâmetros ( rE, rC , IS, nF, ISE, nE, ISC, nC, bF e bR). Derivamos tambem o modelo de pequenos sinais a partir do modelo DC e estudamos uma metodologia de extracao deste modelo a partir de medidas de parâmetros S do dispositivo. A extracao nao foi possivel devido aos altos efeitos parasitarios decorrente das estruturas de testes de microondas. Nos apresentamos solucoes para reduzir estes efeitos. Realizamos medidas e comparamos tres tipos diferentes de dispositivos: transistores bipolares de homojuncao , transistores bipolares de heterojuncao de AlGaAs/GaAs e transistores bipolares de heterojuncao de InP /InGaAs. Nos transistores de AlGaAs/GaAs que medimos vemos uma ausencia da regiao onde a relacao entre a corrente de coletor e de base e constante, devido a alta taxa de recombinacao lateral. Ja nos transistores de InP /InGaAs que medimos esta regiao existe, mas e devido a alta taxa de recombinacao na regiao neutra de base Abstract
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A nanotecnologia e uma area nova e promissora que englobam muitas disciplinas de ciencia e engenharia. Seu rapido crescimento nas ultimas duas decadas e devido ao crescimento simultâneo na fabricacao e caracterizacao de materiais em... more
A nanotecnologia e uma area nova e promissora que englobam muitas disciplinas de ciencia e engenharia. Seu rapido crescimento nas ultimas duas decadas e devido ao crescimento simultâneo na fabricacao e caracterizacao de materiais em escala nanometrica. O objetivo deste trabalho e desenvolver uma tecnica de processo hibrido para a fabricacao de micro e nanocontatos assim como sua caracterizacao eletrica. Esse processo hibrido combina a fotolitografia seguida da tecnica de lift-off e a deposicao de platina por FIB. Para determinar a resistividade da platina depositada por FIB (Focuded Ion Beam), foram fabricas estruturas quadradas variando sua espessura de 5 nm - 100 nm e sua area 150 µm 150 µm e 20 µm x 20 µm. Resistores com comprimento de 30 µm variando sua area de seccao (50 nm x 50 nm - 1 µm x 1 µm) foram fabricados a fim de uma melhor na caracterizacao do processo de deposicao do filme de Pt assim como sua caracterizacao eletrica. As medidas eletricas foram realizadas na estacao Keythley 4200 SCS, onde foi utilizado o metodo de quatro pontas nas estruturas quadradas para a caracterizacao da resistividade. Nos resistores utilizamos a configuracao de dois terminais para a caracterizacao de resistencia dos nanocontatos Abstract
Research Interests: Physics and Humanities
SiGe alloy has become a major material for electronic devices, as part of BiCMOS, CMOS and Optoelectronic systems. The deposition low thermal budget makes SiGe also suitable for MEMS applications. In this paper authors report analysis of... more
SiGe alloy has become a major material for electronic devices, as part of BiCMOS, CMOS and Optoelectronic systems. The deposition low thermal budget makes SiGe also suitable for MEMS applications. In this paper authors report analysis of polycrystalline SiGe thin films by means of Elipsometry, micro-Raman Spectroscopy RBS, and 4 Point Probe measurements. The samples were deposited in a pancake vertical LPCVD system using Silane and Germane as precursor gases in a Hydrogen carrier flow. Ge fraction (x) higher than 30 % and resistivity below 1 mΩ.cm are achieved.
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The regulated cascode (RGC) is a widely used topology in transimpedance amplifiers projects. Although it is efficient with respect to power consumption and bandwidth, the regulated cascode presents high input-referred current noise levels... more
The regulated cascode (RGC) is a widely used topology in transimpedance amplifiers projects. Although it is efficient with respect to power consumption and bandwidth, the regulated cascode presents high input-referred current noise levels that hinder the use of this topology in long distance optical networks. In this paper is proposed a design methodology for CMOS transimpedance amplifiers based on shunt-shunt feedback topology to achieve a broad-band response with low input referred current noise. A complete analysis of the shunt-shunt amplifier is presented. Experimental results shown a 51 dBΩ transimpedance gain and a 10.54GHz bandwidth. The achieved average input referred current noise equals to 6.8 pA/√(Hz), the lowest one between other state-of-art CMOS designs. The circuit was manufactured in 130 nm RF CMOS technology.
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In this work we report the results of the fabrication and simulation of antireflective coating (ARC) of SiO 2 deposited on a silicon substrate, to various thickness. We found that for a thickness of 100nm of SiO 2 ARC we have high... more
In this work we report the results of the fabrication and simulation of antireflective coating (ARC) of SiO 2 deposited on a silicon substrate, to various thickness. We found that for a thickness of 100nm of SiO 2 ARC we have high transmittance on a broad spectral range 500-1000nm. We also obtained maximum transmittance in the three basic colors for the thickness value of 70nm, with values that oscillate between 80 e 85 %. However the values are almost punctual and are in small spectral range of +/- 30nm. The film thickness between 100 and 420 nm were found by ellipsometry by using a fixed refractive index of 1.46. The ARCs were obtained from the plasma source of the Electron Cyclotron Resonance-Chemical Vapor Deposition (ECR-CVD), at room temperature. Spectroscopic properties of SiO2 films, studied through Fourier transform infrared spectroscopy (FTIR), revealed a high structural quality and the presence of Si-O bonds.
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The development of new devices with micron and submicron dimensions requires an accurate photolithographic process steps control. The requirements are different for isolated and periodic/high-density structures. Characterization of a... more
The development of new devices with micron and submicron dimensions requires an accurate photolithographic process steps control. The requirements are different for isolated and periodic/high-density structures. Characterization of a lithographic patterning process are presented, and the conditions of the process are optimized to obtain repetitive pattern transfer for micron and submicron scale technology with high accuracy using the equipments conventionally employed for 2 μm technology. It has been also shown that the technology in the over-exposure regime can be used to obtain -100 nm line structures.
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Stress behavior of thick polycrystalline Silicon (poly-Si) films deposited by vertical low pressure CVD (LPCVD) has been investigated using micro-Raman spectroscopy. Poly-Si films of 0.5 μm thickness and of variable thickness up to 4.5 μm... more
Stress behavior of thick polycrystalline Silicon (poly-Si) films deposited by vertical low pressure CVD (LPCVD) has been investigated using micro-Raman spectroscopy. Poly-Si films of 0.5 μm thickness and of variable thickness up to 4.5 μm were obtained varying deposition temperature and time of deposition. The samples of the first group were subjected to rapid thermal annealing at various temperatures, and samples of the second group used to evaluate influence of thickness on stress behavior. Analyzed poly-Si samples of 0.5μm thickness, exhibited an increasing tensile stress behavior for low RTA temperatures, and for high annealing temperatures a reduction in tensile stress. Poly-Si films of different thickness presented an oscillating tensile stress behavior between 0 and 150MPa for films thinner than 2.0 μm and a stabilizing value of 50 MPa for thicker ones.
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One of the main challenges in manufacturing large area LED Panels with high number of pixels is the requirement of a large number of drivers with enough capacity to provide sufficient power to lit all LEDs at their maximum luminosity.... more
One of the main challenges in manufacturing large area LED Panels with high number of pixels is the requirement of a large number of drivers with enough capacity to provide sufficient power to lit all LEDs at their maximum luminosity. Unlike other systems, such as LCD televisions, the power demand of a large LED panel is critical when all LEDs are on at full brightness. Considering any random video or image to display, it is relatively common such critical situation due to the occurrence of white frames, white lines or columns. Drivers are usually under-dimensioned for such conditions in order to reduce costs which requires that the video content needs to be manually processed and altered in order to prevent the drivers to overload. This paper presents a real-time data monitoring to automatically reduce the brightness depending on the frames displayed on a large scale LED panel. It employs a PWM algorithm implemented into a FPGA that takes into account the inferred power and if it e...
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Neste trabalho estudamos duas tecnicas de dopagem em semicondutores: difusao e implantacao ionica. Realizamos difusao de Estanho em Arseneto de Galio utilizando como fonte de difusao um filme "Spin-on-Glass" (SOG) dopado,... more
Neste trabalho estudamos duas tecnicas de dopagem em semicondutores: difusao e implantacao ionica. Realizamos difusao de Estanho em Arseneto de Galio utilizando como fonte de difusao um filme "Spin-on-Glass" (SOG) dopado, atraves de processamento termico rapido. O filme SOG serve tanto de fonte como de protecao da superficie do GaAs contra a perda de Arsenio. Obtivemos camadas n+ rasas, com alta concentracao de superficie (1-3.1018cm-3) e boa mobilidade (em media 1000cm2 / V.s). Estabelecemos um modelo para a difusao de Estanho dependente da sobre-pressao de vapor de Arsenio baseado nos defeitos pontuais gerados na interface SiO2/GaAs. O uso de sobre-pressao de As reduz as reacoes entre o SiO2 e o GaAs, produzindo assim menos defeitos pontuais (VGa e GaI, entre outros), resultando em menor coeficiente de difusao e maior energia de ativacao. A adicao de Galio no filme SOG tem o mesmo efeito, porem em bem menor intensidade. Realizamos tambem implantacao ionica de Magnesio em GaAs. Foram feitas implantacoes simples e dupla, co-implantando Fosforo. Estudamos o comportamento do Magnesio durante o recozimento pos-implantacao. Para dose de 1.1014cm-2 e energia de 200ke V, obtivemos altas ativacoes. Os melhores resultados foram obtidos para recozimento a 900°C/5, 10 e 20s e a 950°C/5s. Com o aumento da dose (1.1015cm-2/100keV), a ativacao cai. Porem, quando realizamos a dupla-implantacao utilizando mesma .dose e energia, a ativacao triplicou. Isto demonstrou que o Fosforo esta realmente ocupando as vacâncias de Arsenio, aumentando, assim, as vacâncias de Galio ( que serao ocupadas pelo Mg). Estudamos os diversos mecanismos de difusao do Magnesio, incluindo difusao "uphill". Portanto, tanto no caso da difusao de Estanho, quanto na ativacao do Magnesio durante o recozimento, observa-se o efeito de defeitos pontuais tipo VGa e GaI. Isto e esperado pelo fato de ambos os dopantes tenderem a substituir posicoes de Galio. Este conhecimento permite a otimizacao dos processos pelo controle da geracao destes defeitos pontuais Abstract
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The results of a study of SiN x , SiO 2 and Si etching in a high-density ECR plasma using mixtures containing SF 6 , NF 3 , N 2 , O 2 and Ar are presented. Higher selectivities of SiN x etching over SiO 2 (up to ~100) were achieved with... more
The results of a study of SiN x , SiO 2 and Si etching in a high-density ECR plasma using mixtures containing SF 6 , NF 3 , N 2 , O 2 and Ar are presented. Higher selectivities of SiN x etching over SiO 2 (up to ~100) were achieved with NF 3 , while higher selectivities over Si (up to 5-10) were obtained with SF 6 based mixtures. Plasma and surface processes responsible for etching are analyzed.
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ABSTRACTSilicon nitride (SiNx) films with extremely low interface charge densities have been developed by electron cyclotron resonance-chemical vapor deposition (ECR-CVD) deposition on GaAs substrates. The procedure is a one-step process... more
ABSTRACTSilicon nitride (SiNx) films with extremely low interface charge densities have been developed by electron cyclotron resonance-chemical vapor deposition (ECR-CVD) deposition on GaAs substrates. The procedure is a one-step process and does not involve H2 and/or N2 pre-treatment of the sample surface. Characterization by Fourier transform infrared (FTIR) and ellipsometry analysis indicate good properties of the film revealing N-H and Si-N bonds. Results of capacitance-voltage (C–V) measurements show surface charge densities on the order of 5 × 1010 cm−2, which we believe is the lowest surface charge density achieved so far over GaAs.
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Abstract Tungsten etching has been studied in audio frequent plasmas with NF3-O2 and SF6-O2 mixtures. The influence of etch mode, gas flows, pressure and power has been investigated. It is possible to etch tungsten chemically but large... more
Abstract Tungsten etching has been studied in audio frequent plasmas with NF3-O2 and SF6-O2 mixtures. The influence of etch mode, gas flows, pressure and power has been investigated. It is possible to etch tungsten chemically but large concentrations of free fluorine are needed. These are supplied more easily by NF3 than by SF6. During chemical etching with NF3 fluorine diffuses into the tungsten. When in contact with air, the fluorine is replaced by oxygen, forming a tungsten oxide layer, which withstands further chemical etching.
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Research Interests: Engineering, Materials Science, Raman Spectroscopy, Photoluminescence, Chemical Vapor Deposition, and 12 moreNanocrystalline Material, Films, Luminescence, Germanium, Ion Implantation, CHEMICAL SCIENCES, Silicon Oxide, Fourier transform infrared spectroscopy, Germanium Nanocrystals, Raman Scattering, Electroluminescence, and Violet
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Page 1. Advances in the Process and in the Methodology of Emulsion Optical Masks Construction Daniel S. de Lara 1, Luiz Otávio de Saraiva Ferreira 2, Jacobus W. Swart 1 1 Centro de Componentes Semicondutores - Unicamp ...