123,904 research outputs found
AlN/GaN-based MOS-HEMT technology: processing and device results
No full textProcess development of AlN/GaN MOS-HEMTs is presented, along with issues and problems concerning the fabrication processes. The developed technology uses thermally grown Al<sub>2</sub>O<sub>3</sub> as a gate dielectric and surface passivation for devices. Significant improvement in device performance was observed using the following techniques: (1) Ohmic contact optimisation using Al wet etch prior to Ohmic metal deposition and (2) mesa sidewall passivation. DC and RF performance of the fabricated devices will be presented and discussed in this paper
Modelo compacto de não-linearidades em transistores MOS: [dissertação]
No full textDissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico. Programa de Pós-Graduação em Engenharia Elétrica.Neste trabalho, é proposto um modelo compacto para não-linearidades em transistores MOS desenvolvido com base nas equações de canal curto do modelo #Advanced Compact MOSFET# (ACM). As maiores vantagens deste modelo são a simplicidade de suas equações e a forma explícita com que se determinam as nãolinearidades do transistor MOS em função do nível de inversão. Além disso, são discutidas as causas físicas de um aumento de linearidade observado em inversão moderada, chamado #Sweet Spot#. Através de medidas, concluiu-se que efeitos de segunda ordem, principalmente a saturação da velocidade dos portadores em transistores de canal curto, são as principais causas do aumento de linearidade observado. In this work, a compact model for nonlinearities in MOS transistors derived from the short-channel equations of the Advanced Compact MOSFET (ACM) is proposed. The main advantages of the referred model are simplicity of the equations and the explicit determination of the nonlinearities of the MOSFET with respect to the inversion level. In addition, the physical causes of a linearity improvement observed in moderate inversion level, called #Sweet Spot#, are discussed. The measurements shown that second order effects, principally the carrier velocity saturation in short-channel transistors, are the main causes of the linearity improvement observed
Modelo do descasamento (Mismatch) entre transistores MOS: [tese]
No full textTese (Doutorado) - Universidade Federal de Santa Catarina, Centro Tecnológico. Programa de Pós-graduação em Engenharia ElétricaDiversos modelos teóricos para o descasamento entre dispositivos na tecnologia MOS foram propostos desde a década de '80, sendo que geralmente estes pecam ou pela simplicidade, sendo válidos apenas sob condições de operação específicas, ou por resultarem em expressões muito complexas, o que torna necessário o uso de pesados recursos computacionais. Esta tese propõe uma abordagem inovadora para a modelagem do descasamento dos transistores de efeito de campo de porta isolada (MOSFETs), chegando a resultados melhores e mais abrangentes que outras propostas já publicadas. Para tanto, as variações microscópicas na corrente que flui pelo dispositivo, resultado das flutuações na concentração de dopantes na região ativa, são contabilizadas levando-se em conta a natureza não-linear do transistor. O resultado é um modelo compacto que prevê o descasamento com grande exatidão e de forma contínua, em todas as condições de operação do transistor, da inversão fraca à forte, e da região linear à saturação, necessitando apenas dois parâmetros de ajuste. Duas versões de circuitos de teste foram desenvolvidas e implementadas em diversas tecnologias, como forma de se obter suporte experimental para o modelo. A versão mais avançada possibilita a caracterização elétrica, de forma totalmente automática, de um grande número de dispositivos. O uso deste modelo substitui com vantagens a tradicional simulação Monte Carlo, que exige grandes recursos computacionais e consome muito tempo, além de oferecer uma excelente ferramenta de projeto manual, como é demonstrado através do desenvolvimento de um conversor digital-analógico, cujo resultado experimental corroborou a metodologia empregada
The impact of low energy proton damage on the operational characteristics of EPIC-MOS CCDs
No full textThe University of Tübingen 3.5 MeV Van de Graaf accelerator facility was used to investigate the effect of low energy protons on the performance of the European Photon Imaging Camera (EPIC), metal–oxide semiconductor (MOS), charge coupled devices (CCDs). Two CCDs were irradiated in different parts of their detecting areas using different proton spectra and dose rates. Iron-55 was the calibration source in all cases and was used to measure any increases in charge transfer inefficiency (CTI) and spectral resolution of the CCDs. Additional changes in the CCD bright pixel table and changes in the low X-ray energy response of the device were examined.
The Monte Carlo code Stopping Range of Ions in Matter (SRIM) was used to model the effect of a 10 MeV equivalent fluence of protons interacting with the CCD. Since the non-ionising energy loss (NIEL) function could not be applied effectively at such low proton energies. From the 10 MeV values, the expected CTI degradation could be calculated and then compared to the measured CTI changes
Um modelo eficiente do transistor MOS para o projeto de circuitos VLSI: [dissertação]
No full textDissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico. Programa de Pós-Graduação em Engenharia Elétrica.Neste trabalho é detalhada a implementação do modelo ACM do transistor MOS no simulador elétrico ELDO (Mentor Graphics). O código foi escrito em linguagem C utilizando a ferramenta UDM (User Definable Model). A carga de inversão é calculada a partir da equação de carga UCCM utilizando um algoritmo que resolve esta equação com apenas uma iteração e com um erro relativo menor do que 10-7. Através de simulações, o modelo implementado foi confrontado com os demais modelos da nova geração (HiSIM, EKV, BSIM5, SP, MM1 e PSP) tanto no que diz respeito à sua qualidade (simetria, cargas e parâmetros de pequenos sinais) como também no que diz respeito à velocidade da simulação. Os resultados mostram que o modelo ACM é uma poderosa e útil ferramenta para simulação e projeto à mão, pois é constituído por equações compactas e precisas, além de possuir um número reduzido de parâmetros
MOS CCDs for the wide field imager on the XEUS spacecraft
No full textIn recent years the XEUS mission concept has evolved and has been the subject of several industrial studies. The mission concept has now matured to the point that it could be proposed for a Phase A study and subsequent flight programme. The key feature of XEUS will be its X-ray optic with collecting area ~30-100x that of XMM. The mission is envisaged at an orbit around the L2 point in space, and is formed from two spacecraft; one for the mirrors, and the other for the focal plane detectors. With a focal length of 50m, the plate scale of the optic is 6.5x that of XMM, which using existing focal plane technology will reduce the effective field of view to a few arc minutes. Cryogenic instrumentation, with detector sizes of a few mm can only be used for narrow field studies of target objects, and a wide field instrument is under consideration using a DEPFET pixel array to image out to a diameter of 5 arcminutes, requiring an array of dimension 70mm. It is envisaged to extend this field of view possibly out to 15 arcminutes through the use of an outer detection ring comprised of MOS CCD
Transistores MOS compostos de baixa condutancia de saida e alta frequencia de ganho unitario
No full textDissertação (mestrado) - Universidade Federal de Santa Catarina. Centro Tecnologico. Inclui apendiceEste trabalho apresenta uma estrutura de transistor MOS composto, formado pela associação em série de dois transistores, sendo que o transistor conectado no terminal de dreno é mais largo do que o transistor conectado no lado da fonte. É mostrado que esta estrutura apresenta características DC idênticas as de um transistor canal longo de largura uniforme. Este transistor composto têmduas grandes vantagens sobre o transistor canal longo equivalente de largura uniforme: economia considerável de área de silício e uma freqüência de ganho unitário mais elevada. Esta estrutura pode ser utilizada para a integração de circuitos analógicos que necessitem de altas velocidade e baixas tensões. A técnica proposta é particularmente adequada para o projeto de circuitos analógicos utilizando a metodologia de "gate-arrays" ("sea-of-transistor")
A Multiproject Chip Approach to the Teaching of Analog MOS LSI and VLSI
No full textMultiproject chip implementation has been used in teaching analog MOS circuit design. After having worked with computer simulation and layout aids in homework problems, students designed novel circuits including several high
performance op amps, an A/D converter, a switched capacitor filter, a 1 K dynamic RAM, and a variety of less conventional MOS circuits such as a VII converter, an AC/DC converter, an AM radio receiver, a digitally-controlled
analog signal processor, and on-chip circuitry for measuring transistor capacitances. These circuits were laid out as part of an NMOS multiproject chip. Several of the designs exhibit a considerable degree of innovation;
fabrication pending, computer simulation shows that some may be pushing the state of the art. Several designs are of interest to digital designers; in fact, the course has provided knowledge and technique needed for detailed
digital circuit design at the gate level
Comparison between ATSR2 stereo, MOS O2-A band and ground-based cloud top heights
No full textA new method to retrieve cloud top heights stereoscopically using the dual-view facility of the
Along Track Scanning Radiometer 2 (ATSR2) instrument is assessed. This assessment is performed
through a comparison of the cloud top heights obtained from ATSR2 stereo and those derived from
a 94-GHz radar, radiosonde profiles and independently from the Modular Optoelectronic Scanner
(MOS) using the O2-A band. The data for this study were collected over the United Kingdom from
September 1998 through March 1999. The results show that the accuracy of the ATSR2 stereo
heights is generally as predicted on theoretical grounds, with the errors in the
1.6 μm and 0.65 μm stereo heights rarely exceeding 2 km. Case study periods with disagreements
between the ATSR2 heights and the ground-based retrievals are often due to the lack of precise
match-ups between the ground-based and satellite scenes, while the MOS O2-A band is shown
sometimes to miss the tops of high clouds. Evidence that the 11 μm channel is more sensitive to
high clouds than originally thought is given and a future application of multi-spectral stereo cloud
top heights is proposed.A new method to retrieve cloud top heights stereoscopically using the dual-view facility of the
Along Track Scanning Radiometer 2 (ATSR2) instrument is assessed. This assessment is performed
through a comparison of the cloud top heights obtained from ATSR2 stereo and those derived from
a 94-GHz radar, radiosonde profiles and independently from the Modular Optoelectronic Scanner
(MOS) using the O2-A band. The data for this study were collected over the United Kingdom from
September 1998 through March 1999. The results show that the accuracy of the ATSR2 stereo
heights is generally as predicted on theoretical grounds, with the errors in the
1.6 μm and 0.65 μm stereo heights rarely exceeding 2 km. Case study periods with disagreements
between the ATSR2 heights and the ground-based retrievals are often due to the lack of precise
match-ups between the ground-based and satellite scenes, while the MOS O2-A band is shown
sometimes to miss the tops of high clouds. Evidence that the 11 μm channel is more sensitive to
high clouds than originally thought is given and a future application of multi-spectral stereo cloud
top heights is proposed
Radiation Hardness of Mos Structures Exposed to High-Energy Ions
No full textMOS structures exposed to 305 MeV Kr and 710 MeV Bi ions irradiation with fluences of 109 cm2 and 1010 cm2 were investigated by capacitance measuring methods (C-V, C-t), completed by quasistatic low-frequency C-V and DLTS measurements.The irradiated MOS structures were functional in spite of a high density of radiation defects. The electric activity of the defects brought a sharp decrease in the generation parameters tr and g. The parameters of six deep levels were detected in the MOS structures exposed to 710 MeV Bi ions irradiation. Five of these levels with energies 0.52 eV, 0.14 eV, 0.17 eV, 0.25 eV, 0.27 eV were radiation defects
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