Name: mos capacitor voltage and charge
Uploaded: 2024-07-08T13:20:41.000Z
Duration: 1 min 25 s
Channel: JoVE

Os capacitores MOS têm três camadas: a camada inferior é um substrato semicondutor, a intermediária é uma camada isolante e a camada superior de metal é o eletrodo de porta, que controla a tensão do capacitor.
Com tensão de porta zero, nenhuma corrente flui e o capacitor não é carregado.
A aplicação de uma tensão negativa na porta atrai furos para a superfície do semicondutor, formando uma região de acumulação. O dispositivo se comporta como um capacitor convencional.
Aplicando uma tensão positiva, os orifícios são repelidos de volta ao substrato, estabelecendo uma região de carga espacial chamada região de depleção, que atua como outra capacitância em série.
Com uma voltagem alta o suficiente, a concentração de elétrons na superfície aumenta, formando uma camada de inversão e diminuindo ainda mais a capacitância. Isso resulta em um aumento acentuado na corrente.
A remoção da tensão dissipa a carga acumulada, fazendo com que o canal desapareça e desligando o dispositivo.
Os capacitores MOS são usados em dispositivos de memória como DRAM, onde a gravação de dados envolve a aplicação de tensão de porta para criar uma camada de inversão, que armazena carga temporariamente. A presença ou ausência dessa carga representa dados binários, que precisam de atualização periódica devido à sua natureza transitória.

capacitor mos

Um capacitor de semicondutor de óxido metálico (MOS) é uma estrutura fundamental usada extensivamente na tecnologia de dispositivos semicondutores, particularmente na fabricação de circuitos integrados e MOSFETs (transistores de efeito de campo semicondutores de óxido metálico). O capacitor MOS consiste em três camadas: uma porta metálica, um óxido dielétrico e um substrato semicondutor.
A porta metálica é normalmente feita de materiais altamente condutores, como alumínio ou polisilício. Abaixo da porta metálica encontra-se uma fina camada de óxido isolante, geralmente dióxido de silício (SiO_2), que é o dielétrico. O substrato semicondutor é comumente silício, que pode ser do tipo p ou do tipo n.
Quando uma tensão é aplicada à porta metálica, ela influencia a distribuição dos portadores elétricos no semicondutor. As bandas de energia do semicondutor são planas quando a tensão aplicada é zero, indicando que não há excesso de carga dentro do óxido ou na superfície do semicondutor. À medida que a tensão da porta aumenta positivamente, ela atrai elétrons para a interface do óxido e do semicondutor. Isso cria um acúmulo de elétrons no silício tipo n e um esgotamento de lacunas no silício tipo p, formando a camada de depleção.
Um aumento adicional na tensão leva a uma forte inversão, onde a superfície semicondutora abaixo do óxido muda de tipo; por exemplo, um tipo p torna-se um tipo n, à medida que os elétrons se tornam os portadores majoritários. Esta camada de inversão é crítica na operação dos MOSFETs. A capacitância da estrutura MOS varia com a tensão aplicada à porta.
A camada de inversão é crucial para o funcionamento dos capacitores MOS na DRAM. A gravação de dados envolve a aplicação de uma tensão que cria essa camada e o armazenamento da carga no semicondutor. Essa carga armazenada representa dados binários, possibilitando o armazenamento e recuperação de informações. A remoção da tensão faz com que a carga se dissipe, desativando o canal e preservando os dados armazenados. Este ciclo de carga é fundamental para a funcionalidade e confiabilidade da DRAM em aplicações de computação.

Capacitor MOS

Os capacitores MOS têm três camadas: a camada inferior é um substrato semicondutor, o meio é uma camada isolante e a camada superior de metal é a porta ...

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MOS Capacitor

mos capacitor voltage and charge

A MOS capacitor uses voltage to control charge in a semiconductor. It is a key structure in semiconductor device technology and in the fabrication of integrated circuits and MOSFETs, or metal-oxide-semiconductor field-effect transistors.

The structure has three layers. A metal gate sits on top and is usually made from a highly conductive material such as aluminum or polysilicon. Below it is a thin insulating oxide layer, usually silicon dioxide (SiO2), and below that is a semiconductor substrate, often silicon that can be p-type or n-type.

At zero applied voltage, the semiconductor energy bands are flat. This means there is no excess charge in the oxide or at the semiconductor surface. When a positive voltage is applied to the gate, it changes how charge carriers are distributed in the semiconductor.

A positive gate voltage attracts electrons toward the oxide-semiconductor interface. In n-type silicon, this creates electron accumulation. In p-type silicon, it causes holes to leave the surface region, which forms a depletion layer.

If the voltage increases further, strong inversion occurs. In this state, the semiconductor surface beneath the oxide changes type. For example, a p-type surface can behave like n-type material because electrons become the majority carriers. This inversion layer is important for MOSFET operation.

The capacitance of a MOS structure changes with the gate voltage. In DRAM, this inversion layer is used to write data by applying a voltage and storing charge in the semiconductor. The stored charge represents binary data. When the voltage is removed, the charge dissipates, the channel turns off, and the stored data is preserved.

MOS Capacitor Voltage and Charge

bipolar junction transistor

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BJT Amplifier Response at Low and High Freq

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BJT Amplifier Gain and Input Resistance

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mos capacitor

A MOS capacitor uses voltage to control charge in a semiconductor. It is a key structure in semiconductor device technology and in the fabrication of integrated circuits and MOSFETs, or metal-oxide-semiconductor field-effect transistors. The structure has three layers. A metal gate sits on top and is usually made from a highly conductive material such as aluminum or polysilicon. Below it is a thin insulating oxide layer, usually silicon dioxide (SiO2), and below that is a semiconductor...

mosfet

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MOSFET Structure and Operating Regions

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small-signal analysis of mosfet amplifiers

small-signal-analysis-of-mosfet-amplifiers

MOSFET Amplifier Gain and Signal Distortion

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key terms and concepts

Learn how a MOS capacitor uses gate voltage to move charge, form depletion and inversion layers, and store data in DRAM.

MOS Capacitor Voltage and Charge | JoVE K12

JoVE Core Electrical Engineering offers easy-to-understand animated videos that cover fundamental concepts of electric circuits along with circuit analysis techniques. It incorporates first-order and second-order circuits using operational amplifiers and circuit transformation concepts. The inclusion of practical design examples and real-world applications through scientist-in-action videos adds significant educational value, making complex concepts accessible.

electrical engineering

MOS Capacitor Voltage and Charge

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