Estudo comparativo do comportamento elétrico entre os MOSFETS dos tipos wave e convencionais equivalentes operando em ambientes de radiações ionizantes
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Tese
Data
2016
Autores
Souza, Rafael Navarenho de
Orientador
Gimenez, S. P.
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SOUZA, Rafael Navarenho de. Estudo comparativo do comportamento elétrico entre os MOSFETS dos tipos wave e convencionais equivalentes operando em ambientes de radiações ionizantes. 2016. 201 f. Tese (Doutorado em Engenharia Elétrica) - Centro Universitário FEI, São Bernardo do Campo, 2016
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Palavras-chave
Radiação,Transistor de efeito de campo de metal-óxido semicondutor,Caracterização elétrica experimental
Resumo
Neste trabalho realizou-se um estudo comparativo experimental entre um novo estilo de leiaute para ser empregado em Metal-Oxide-Semiconductor Field Effect Transistors (MOSFETs), denominado de Wave, cujo formato de porta é semelhante ao da letra “S”, e aos seus respectivos MOSFETs equivalentes de porta retangular, visando as aplicações de circuitos integrados (CIs) analógicos e digitais em ambientes de radiações ionizantes. Dessa
forma, neste estudo são comparados os valores dos principais parâmetros elétricos e figuras de mérito do Wave MOSFET de canal n (WnM) com o MOSFET de canal n convencional (nMOSFET) equivalente (CnM), antes e depois dos procedimentos de irradiação com raios X. Este estudo considera a polarização dos MOSFETs durante os procedimentos de irradiações com raios X, isto é, com os transistores polarizados e não polarizados durante os
procedimentos de radiações ionizantes, considerando-se que eles possuem os mesmos comprimentos de canal, as mesmas condições de polarização e os mesmos fatores geométricos, cujo objetivo é verificar as vantagens e desvantagens deste inovador estilo de leiaute em relação ao leiaute retangular convencional equivalente.
Foram projetados no Centro Universitário da FEI diferentes MOSFETs com geometrias de porta retangulares (convencionais) e do tipo Wave, utilizando-se o processo de fabricação Complementary MOS (CMOS) convencional (Bulk) da AMI Semiconductor (ON Semiconductor) de 0,35 µm, por meio do programa MOSIS Education Program (MEP), os quais foram usados neste trabalho. O MOSFET do tipo Wave é uma evolução do MOSFET com geometria de porta circular e foi especialmente projetado para melhorar o casamento ("matching") entre dispositivos, melhorar o fator de integração de MOSFETs planares de potência (Planar Power MOSFETs, PPMs), aumentar a tensão de ruptura (Breakdown Voltage between Source and Drain, BVDS) e a robustez contra as descargas eletrostáticas (Electrostatic Discharge, ESD) quando comparado aos MOSFETs convencionais de geometria de porta retangular. Além disso, trabalhos realizados por caracterização elétrica e por simulação numérica 3D mostraram
que o Wave nMOSFET é capaz de melhorar o desempenho elétrico dos parâmetros analógicos e digitais em aproximadamente 15%, em média, relativamente ao convencional equivalente. Os efeitos da Dose Ionizante Total (Total Ionizing Dose, TID) podem ser atenuados por meio de estratégias de projeto (Hardening-By-Design, HBD) nas quais os efeitos dos transistores parasitários das regiões de bico de pássaro (BBRs) são reduzidos. O Wave
MOSFET, devido as suas características geométricas, produz um campo elétrico longitudinal 8 radial ao longo do canal e, consequentemente, é capaz de reduzir os efeitos dos transistores parasitários nas BBRs em ambientes de radiações ionizantes. Entretanto, o estilo de leiaute Wave possui um alto campo elétrico longitudinal próximo à região de dreno no semicírculo, o qual está configurado com polarização de dreno interno acarretando, assim, um aumento da corrente de estado desligado (IOFF) em uma década, quando comparado ao convencional equivalente após os efeitos da TID. Portanto, a sua aplicação em ambientes de radiações ionizantes de raios X para CIs digitais pode apresentar limitações quando a IOFF é considerada. Quando as aplicações em CIs CMOS analógicos ocorrem em ambientes de radiações ionizantes de raios X, o WnM é capaz de apresentar um melhor desempenho elétrico em relação aos convencionais equivalentes de porta retangular, pois os transistores parasitários nas BBRs têm uma menor influência do que aqueles encontrados nos CnMs, após a exposição às radiações ionizantes de raios X. Portanto, através deste estudo comparativo experimental, o estilo de leiaute do tipo Wave para MOSFETs apresenta a capacidade de aumentar a frequência de ganho de tensão unitário (fT) e o ganho de tensão de malha aberta (AV0), em média, 20% e 10%, respectivamente, em relação ao estilo de leiaute convencional (retangular) equivalente, considerando-se que esses MOSFETs apresentam as mesmas áreas de porta e condições de polarização. Desta forma, o MOSFET do tipo Wave pode ser considerado uma outra alternativa de leiaute para a implementação de MOSFETs, objetivando-se principalmente as aplicações de CIs CMOS analógicos em ambientes de radiações ionizantes de raios X.
This work presents an experimental comparative study between a new layout structure to be applied in Metal-Oxide-Semiconductor Field Effect Transistors (MOSFETs), called Wave, whose the format of the gate is similar to the letter "S", and the equivalents MOSFETs with rectangular gate, aiming applications in analog and digital integrated circuits (ICs) in ionizing radiation environments. Thus, this study compares the values of the main electrical parameters and figures of merit of the Wave n-channel MOSFET (WnM) with the n-channel MOSFET (nMOSFET) equivalent conventional (CnM), before and after the irradiation procedures with X-rays. This study takes into account the biasing of the MOSFETs during the irradiation procedures with X-rays, i.e. with biased and unbiased transistors during the ionizing irradiation procedures, considering that they have the same channel lengths, the same conditions of biasing and the same geometric factors, in order to verify the advantages and disadvantages of this innovative layout style compared to the equivalent conventional rectangular layout. It was designed, at the University Center of FEI, MOSFETs with rectangular gate geometries (conventional) and Wave, using the Complementary MOS (CMOS) conventional manufacturing process (Bulk) from AMI Semiconductor (ON Semiconductor) of 0.35 µm via MOSIS Education Program (MEP) program, which were used in this study. The Wave MOSFET is an evolution of the MOSFET with circular gate geometry and was especially designed to improve the matching between devices, to improve the geometric factor of Planar Power MOSFETs (PPMs), to increase the Breakdown Voltage between Source and Drain (BVDS), and the robustness against Electrostatic Discharge (ESD) when compared to the conventional MOSFETs with rectangular gate geometry. Furthermore, studies conducted by electrical characterization and 3D numerical simulation showed that the Wave nMOSFET is capable of improving the electrical performance of analog and digital parameters by approximately 15% on average compared to the equivalent conventional. The effects of the Total Ionizing Dose (TID) can be attenuated by design strategies (Hardening-by-Design, HBD) in which the effects of the parasitic transistors in the bird's beak regions (BBRs) are reduced. The Wave MOSFET, due to its geometric characteristics, produces a longitudinal electrical field which is radial along the channel, and therefore it is able to reduce the effects of the parasitic transistors in the BBRs in the ionizing radiation environments. However, the Wave layout style has a high longitudinal electrical field close to the drain region in the semicircle which is configured with internal drain bias, resulting in an 10 increased OFF State current (IOFF) in a decade when compared to the equivalent conventional after the effects of the TID. Therefore, its application in the ionizing radiation environments for digital ICs is likely to be limited when it takes into account IOFF. Regarding the applications in the analog ICs CMOS in X-rays ionizing radiation environments, the WnM is able to present better electrical performance in relation to the equivalent conventional with rectangular gate, due to the fact that the parasitic transistors in the BBRs have less influence than those found in the CnMs after the exposure to X-rays ionizing radiation. Therefore, through this experimental comparative study, the Wave layout for MOSFETs presents the capability to increase the unity voltage gain frequency (fT) and the open loop voltage gain (AV0), on average, 20% and 10%, respectively, in relation to the conventional (rectangular) layout style, considering that these MOSFETs have the same gate areas and polarization conditions. Thus, the Wave MOSFET can be considered another alternative of layout for the implementation of MOSFETs.
This work presents an experimental comparative study between a new layout structure to be applied in Metal-Oxide-Semiconductor Field Effect Transistors (MOSFETs), called Wave, whose the format of the gate is similar to the letter "S", and the equivalents MOSFETs with rectangular gate, aiming applications in analog and digital integrated circuits (ICs) in ionizing radiation environments. Thus, this study compares the values of the main electrical parameters and figures of merit of the Wave n-channel MOSFET (WnM) with the n-channel MOSFET (nMOSFET) equivalent conventional (CnM), before and after the irradiation procedures with X-rays. This study takes into account the biasing of the MOSFETs during the irradiation procedures with X-rays, i.e. with biased and unbiased transistors during the ionizing irradiation procedures, considering that they have the same channel lengths, the same conditions of biasing and the same geometric factors, in order to verify the advantages and disadvantages of this innovative layout style compared to the equivalent conventional rectangular layout. It was designed, at the University Center of FEI, MOSFETs with rectangular gate geometries (conventional) and Wave, using the Complementary MOS (CMOS) conventional manufacturing process (Bulk) from AMI Semiconductor (ON Semiconductor) of 0.35 µm via MOSIS Education Program (MEP) program, which were used in this study. The Wave MOSFET is an evolution of the MOSFET with circular gate geometry and was especially designed to improve the matching between devices, to improve the geometric factor of Planar Power MOSFETs (PPMs), to increase the Breakdown Voltage between Source and Drain (BVDS), and the robustness against Electrostatic Discharge (ESD) when compared to the conventional MOSFETs with rectangular gate geometry. Furthermore, studies conducted by electrical characterization and 3D numerical simulation showed that the Wave nMOSFET is capable of improving the electrical performance of analog and digital parameters by approximately 15% on average compared to the equivalent conventional. The effects of the Total Ionizing Dose (TID) can be attenuated by design strategies (Hardening-by-Design, HBD) in which the effects of the parasitic transistors in the bird's beak regions (BBRs) are reduced. The Wave MOSFET, due to its geometric characteristics, produces a longitudinal electrical field which is radial along the channel, and therefore it is able to reduce the effects of the parasitic transistors in the BBRs in the ionizing radiation environments. However, the Wave layout style has a high longitudinal electrical field close to the drain region in the semicircle which is configured with internal drain bias, resulting in an 10 increased OFF State current (IOFF) in a decade when compared to the equivalent conventional after the effects of the TID. Therefore, its application in the ionizing radiation environments for digital ICs is likely to be limited when it takes into account IOFF. Regarding the applications in the analog ICs CMOS in X-rays ionizing radiation environments, the WnM is able to present better electrical performance in relation to the equivalent conventional with rectangular gate, due to the fact that the parasitic transistors in the BBRs have less influence than those found in the CnMs after the exposure to X-rays ionizing radiation. Therefore, through this experimental comparative study, the Wave layout for MOSFETs presents the capability to increase the unity voltage gain frequency (fT) and the open loop voltage gain (AV0), on average, 20% and 10%, respectively, in relation to the conventional (rectangular) layout style, considering that these MOSFETs have the same gate areas and polarization conditions. Thus, the Wave MOSFET can be considered another alternative of layout for the implementation of MOSFETs.