Trapezoidal SOI FinFET analog parameters` dependence on cross-section shape

The trapezium is often a better approximation for the FinFET cross-section shape, rather than the design-intended rectangle. The frequent width variations along the vertical direction, caused by the etching process that is used for fin definition, may imply in inclined sidewalls and the inclination angles can vary in a significant range. These geometric variations may cause some important changes in the device electrical characteristics. This work analyzes the influence of the FinFET sidewall inclination angle on some relevant parameters for analog design, such as threshold voltage, output conductance, transconductance, intrinsic voltage gain (A V), gate capacitance and unit-gain frequency, through 3D numeric simulation. The intrinsic gain is affected by alterations in transconductance and output conductance. The results show that both parameters depend on the shape, but in different ways. Transconductance depends mainly on the sidewall inclination angle and the fixed average fin width, whereas the output conductance depends mainly on the average fin width and is weakly dependent on the sidewall inclination angle. The simulation results also show that higher voltage gains are obtained for smaller average fin widths with inclination angles that correspond to inverted trapeziums, i.e. for shapes where the channel width is larger at the top than at the transistor base because of the higher attained transconductance. When the channel top is thinner than the base, the transconductance degradation affects the intrinsic voltage gain. The total gate capacitances also present behavior dependent on the sidewall angle, with higher values for inverted trapezium shapes and, as a consequence, lower unit-gain frequencies.

Threshold voltages of SOI MuGFETs

The multiple-gate field-effect transistor (MuGFET) is a device with a gate folded on different sides of the channel region. They are one of the most promising technological solutions to create high-performance ultra-scaled SOI CMOS. In this work, the behavior of the threshold voltage in double-gate, triple-gate and quadruple-gate SOI transistors with different channel doping concentrations is studied through three-dimensional numerical simulation. The results indicated that for double-gate transistors, one or two threshold voltages can be observed, depending on the channel doping concentration. However, in triple-gate and quadruple-gate it is possible to observe up to four threshold voltages due to the corner effect and the different doping concentration between the top and bottom of the Fin. (C) 2008 Elsevier Ltd. All rights reserved.

Improved generation lifetime model for the electrical characterization of single- and double-gate SOI nMOSFETs

This work proposes a refined technique for the extraction of the generation lifetime in single- and double-gate partially depleted SOI nMOSFETs. The model presented in this paper, based on the drain current switch-off transients, takes into account the influence of the laterally non-uniform channel doping, caused by the presence of the halo implanted region, and the amount of charge controlled by the drain and source junctions on the floating body effect when the channel length is reduced. The obtained results for single- gate (SG) devices are compared with two-dimensional numerical simulations and experimental data, extracted for devices fabricated in a 0.1 mu m SOI CMOS technology, showing excellent agreement. The improved model to determine the generation lifetime in double-gate (DG) devices beyond the considerations previously presented also consider the influence of the silicon layer thickness on the drain current transient. The extracted data through the improved model for DG devices were compared with measurements and two-dimensional numerical simulations of the SG devices also presenting a good adjustment with the channel length reduction and the same tendency with the silicon layer thickness variation.

Temperature influence on the gate-induced floating body effect parameters in fully depleted SOI nMOSFETs

The temperature influence on the gate-induced floating body effect (GIFBE) in fully depleted (FD) silicon-on-insulator (SOI) nMOSFETs is investigated, based on experimental results and two-dimensional numerical simulations. The GIFBE behavior will be evaluated taking into account the impact of carrier recombination and of the effective electric field mobility degradation on the second peak in the transconductance (gm). This floating body effect is also analyzed as a function of temperature. It is shown that the variation of the studied parameters with temperature results in a ""C"" shape of the threshold voltage corresponding with the second peak in the gm curve. (C) 2008 Elsevier Ltd. All rights reserved.

Analysis of source-follower buffers implemented with graded-channel SOI nMOSFETs operating at cryogenic temperatures

This work studies the operation of source-follower buffers implemented with standard and graded-channel (GC) fully depleted (FD) SCI nMOSFETs at low temperatures. The analysis is performed by comparing the voltage gain of buffers implemented with GC and standard SOI nMOS transistors considering devices with the same mask channel length and same effective channel length. It is shown that the use of GC devices allows for achieving improved gain in all inversion levels in a wide range of temperatures. In addition, this improvement increases as temperature is reduced. It is shown that GC transistors can provide virtually constant gain, while for standard devices, the gain departs from the maximum value depending on the temperature and inversion level imposed by the bias current and input voltage. Two-dimensional numerical simulations were performed in order to study the reasons for the enhanced gain of GC MOSFETs at low temperatures. (C) 2009 Elsevier Ltd. All rights reserved.

Advantages of graded-channel SOI nMOSFETs for application as source-follower analog buffer

In this work the performance of graded-channel (CC) SOI MOSFETs operating as source-follower buffers is presented. The experimental analysis is performed by comparing the gain and linearity of buffers implemented with CC and standard SOI MOS devices considering the same mask dimensions. It is shown that by using CC devices, buffer gain very close to the theoretical limit can be achieved, with improved linearity, while for standard devices the gain departs from the theoretical value depending on the inversion level imposed by the bias current and input voltage. Two-dimensional numerical simulations were performed in order to confirm some hypotheses proposed to explain the gain behavior observed in the experimental data. By using numerical simulations the channel length has been varied, showing that the gain of buffers implemented with CC devices remains close to the theoretical limit even when short-channel devices are adopted. It has also been shown that the length of a source-follower buffer using CC devices can be reduced by a factor of 5, in comparison with a standard Sol MOSFET, without gain loss or linearity degradation. (C) 2008 Elsevier Ltd. All rights reserved.

As vivências: questões de tradução, sentidos e fontes epistemológicas no legado de Vigotski

O objetivo deste artigo é abordar a questão das vivências na perspectiva de L.S. Vigotski, tratando de suas fontes epistemológicas, de suas raízes na língua russa e de seus sentidos específicos, priorizando "A Tragédia do Hamlet, Príncipe da Dinamarca" (1916) e os textos pedológicos dos anos 1930, com destaque para "A questão do meio na pedologia". Destacam-se as transformações das ideias do autor sobre vivências e sua contribuição metodológica à  análise da relação indivíduo-meio no desenvolvimento humano, articulada aos conceitos de consciência e sistema.

O conceito de vivência em Freud e Husserl

Este artigo visa explicitar as concepções freudiana e husserliana de “vivência” (Erlebnis). Por “vivência” entende-se genericamente um tipo fundamental de experiência do mundo. Esse tema, ainda que não diretamente explorado por Freud, tornou-se necessário em sua teoria desde a descoberta da etiologia da histeria no início dos anos 1890 à luz do método catártico: a da vivência traumática. Por outro lado, Husserl, a partir do problema filosófico de garantir a possibilidade do conhecimento universal e necessário, se viu obrigado a combater o naturalismo das ideias, em 1900, e o naturalismo da consciência, em 1913, em ambos os casos partindo de uma análise das vivências (intencionais). Mostrarei que a abordagem freudiana (natural-científica) visa explicar metapsicologicamente a vivência, ao passo que a abordagem husserliana pretende descrever a estrutura da vivência (intencional). Por fim, apontarei para algumas das grandes diferenças entre ambas as abordagens desse tema.

Matrizes clínicas e ética em Freud

O presente estudo hipotetiza que as diferentes matrizes clínicas que Freud encontrava em sua prática, e que lhe possibilitavam acréscimos teóricos, direcionaram seus distintos olhares sobre a cultura, fazendo-o privilegiar alguns elementos éticos em detrimento de outros. Desse modo, indicaremos: (1) como a histeria gerou a questão do conflito entre sexualidade e moral na civilização; (2) como a neurose obsessiva possibilitou a entrada dos temas da agressividade e do ódio como entraves contra os quais a cultura se esforça por lutar, assim como a presença marcante no psiquismo da consciência moral e do sentimento de culpa; (3) por fim, como as ditas afecções narcísicas trouxeram a Freud o papel do egoísmo e da destrutividade como inimigos da cultura. Nesse percurso nos aproximaremos das questões ligadas à problematização ética na "psicologia" freudiana e, a partir daí, do destaque que terá a dimensão moral na concepção freudiana do sujeito.

Pós-alta em Hanseníase no Ceará: limitação da atividade funcional, consciência de risco e participação social

Caracterizar a limitação funcional, de atividade, consciência de risco, e restrição à participação social em pessoas atingidas pela hanseníase no pós-alta. Estudo seccional-descritivo com 69 residentes em Sobral, Ceará, com alta entre 2003 a 2005. Foram realizados exame físico dermato-neurológico, avaliação demográfica, de limitação funcional-atividade-consciência de risco e de restrição à participação social. Vinte (28,9%) apresentaram escores SALSA 19 e 20 e escore EHF zero. O maior escore EHF foi alcançado por dois participantes, com 25 e 28 na escala SALSA. Na escala de participação 37 (53,6%) não apresentaram restrição e tinham escore EHF zero. Dois (2,9%) com escore EHF zero tinham leve restrição e 1 (1,5%), grande restrição. Reafirma-se a potencialidade destas ferramentas para a atenção integral aos portadores.

Trapezoidal cross-sectional influence on FinFET threshold voltage and corner effects

Fin field effect transistors (FinFETS) are silicon-on-insulator (SOI) transistors with three-dimensional structures. As a result of some fabrication-process limitations (as nonideal anisotropic overetch) some FinFETs have inclined surfaces, which results in trapezoidal cross sections instead of rectangular sections, as expected. This geometric alteration results in some device issues, like carrier profile, threshold voltage, and corner effects. This work analyzes these consequences based on three-dimensional numeric simulation of several dual-gate and triple-gate FinFETs. The simulation results show that the threshold voltage depends on the sidewall inclination angle and that this dependence varies according to the body doping level. The corner effects also depend on the inclination angle and doping level. (C) 2008 The Electrochemical Society.

Altazor, de Vicente Huidobro: o gesto político numa das epopeias de XX

This article aims at presenting a reading of Vicente Huidobro's poem Altazor (1931,) assuming the epic genre postulations and the conditions of its development in the first half of the twentieth century. Important works were produced in that period, setting in motion a deployment of the epic genre as refashioned by the avant-garde movements and contesting the metaphysical formulations that had considered it impossible as a discursive space in modern times. Altazor is situated in this movement as a self-conscience of issues of language and its objective capacities. The work deals with the possible modes of enunciation of a great poet, Altazor, who lacks his former serenity of old and looks for a language able to transcend his mother tongue, because he does not accept its origin. His political revolution is performed on language, the artifice through which history is told.

Physical and dynamical characterization of (5201) Ferraz-Mello, a possible extinct Jupiter family comet

Context. The subject of asteroids in cometary orbits (ACOs) has been of growing interest lately. These objects have the orbital characteristics typical of comets, but are asteroidal in appearance, i.e., show no signs of a coma at any part of their orbits. At least a fraction of these objects are thought to be comets that have either exhausted all their volatile content or developed a refractory crust that prevents sublimation. In particular, the asteroid ( 5201) Ferraz-Mello has, since its discovery, been suspected to be an extinct Jupiter family comet due to the peculiar nature of its orbit. Aims. The aim of this work is to put constraints on the possible origin of ( 5201) Ferraz-Mello by means of spectroscopic characterization and a study of the dynamics of this asteroid. Methods. We used the SOAR Optical Imager (SOI) to obtain observations of ( 5201) Ferraz-Mello using four SDSS filters. These observations were compared to asteroids listed in the Sloan Moving objects catalog and also to photometry of cometary nuclei, Centaurs, and TNOs. The orbital evolution of ( 5201) Ferraz-Mello and of a sample of asteroids and comets that are close to that object in the a - e plane were simulated using a pure N-body code for 4 000 years forward and 4 000 years backward in time. Results. The reflectance spectrum obtained from its colors in the SDSS system is unusual, with a steep spectral gradient that is comparable to TNOs and Centaurs, but with an increase in the reflectance in the g band that is not common in those populations. A similar behavior is seen in cometary nuclei that were observed in the presence of a faint dust coma. The dynamical results confirm the very chaotic evolution found previously and its dynamical similarity to the chaotic evolution of some comets. The asteroid is situated in the very stochastic layer at the border of the 2/1 resonance, and it has a very short Lyapunov time ( 30 - 40) years. Together, the spectral characteristcs and the dynamical evolution suggest that ( 5201) Ferraz-Mello is a dormant or extinct comet.

Low-frequency noise and static analysis of the impact of the TiN metal gate thicknesses on n- and p-channel MuGFETs

The impact of the titanium nitride (TIN) gate electrode thickness has been investigated in n and p channel SOI multiple gate field effect transistors (MuGFETs) through low frequency noise charge pumping and static measurements as well as capacitance-voltage curves The results suggest that a thicker TIN metal gate electrode gives rise to a higher EOT a lower mobility and a higher interface trap density The devices have also been studied for different back gate biases where the GIFBE onset occurs at lower front-gate voltage for thinner TIN metal gate thickness and at higher V(GF) In addition it is demonstrated that post deposition nitridation of the MOCVD HfSiO gate dielectric exhibits an unexpected trend with TIN gate electrode thickness where a continuous variation of EOT and an increase on the degradation of the interface quality are observed (C) 2010 Elsevier Ltd All rights reserved

Cryogenic operation of FinFETs aiming at analog applications

FinFETs are recognized as promising candidates for the CMOS nanometer era. In this paper the most recent results for cryogenic operation of FinFETs will be demonstrated with special emphasis on analog applications. Threshold voltage, subthreshold slope and carrier mobility will be studied. Also some important figures of merit for analog circuit operation as for readout electronics, such as transconductance, output conductance and intrinsic voltage gain will be covered. It is demonstrated that the threshold voltage of undoped narrow FinFETs is less temperature-dependent than for a planar single-gate device with similar doping concentration. The temperature reduction improves the transconductance over drain current ratio in any operational region. On the other hand, the output conductance is degraded when the temperature is reduced. The combination of these effects shows that the intrinsic gain of a L = 90 nm FinFET is degraded by 2 dB when the temperature reduces from 300 K to 100 K. (C) 2009 Elsevier Ltd. All rights reserved.