Материалы для самостоятельной внеауди­торной работы

(ПОСЛЕ ВТОРОГО ЗАНЯТИЯ)

Учитесь читать и переводить.

Текст 3.12. Прочитайте текст. Изложите свои выводы о преимуществах приборов на арсениде галлия. Используя рисунок, опишите принцип действия прибора. На основе прочитанного и ваших знаний по специальности подго­товьте сообщения о: а) технологии полупроводниковых приборов и ИС; б) новых материалах и новой технологии производства ИС, БИС и СБИС.

Ш-V Semiconductor Integrated Cifcuits

III-V semiconductors attract the attention of scientists and manufacturers working in the field of microelectronics. This inter­est is based upon the ability of these materials to satisfy a wide va­riety of needs.

Technological applications include high speed processing, communications, sensing and imagining, and many others. Integrated circuits with various combinations of MESFET, JFET, bipolar, Gunn, Schottky diode, laser diode, optical detector, light guide, acoustic wave, and other assorted functions are being ex­plored, developed and utilized.

One of the first large-scale applications of Ш-V semi­conductors was light-emitting diodes (LEDs) which are two ter­minal devices that emit light when a forward-bias current is passed through a p-n junction. An energy state and device con­struction is given in Fig. 3.

current flow

contact

radiations

contact

active region

current flow

Рис.3

When an electron in the conduction band combines with a hole in the valence band, the energy is emitted as a photon and light is produced. Of course, non-radiative combination processes and light re-absorption must be minimized for high efficiency. To emit light visible to the human eye, a band gap near 2 eV is neces­sary to provide the proper photon energy, which precludes use of the semiconductors except GaP, which produces red-green light.

At the beginning of the 1970’s, the GaAs MESFET device was developed for use in circuits such as microwave amplifiers oper­ating in the frequencies range from about 2 to 12 GHz. The device is fabricated on a base of single-crystal semi-insulating GaAs. A GaAs film containing a closely-controlled concentration of n-type dopant atoms is epitaxially deposited on the GaAs wafer. The de­vices are completed by etching "mesas" or islands to electrically isolate the device and by adding low resistance contacts and a gate electrode. The gate length is typically 1 µm.

The first integration of GaAs MESFET transistors into logic gates was done in 1974. These gates have been integrated into gated flip-flop integrated circuits and used for prescalers and time-interval measurements. These GaAs integrated circuits operate at substantially higher speeds than silicon ICs because of a combina­tion of higher transconductance due to higher electron mobility, and lower parasitic capacitance due to higher substrate resistivity. The higher substrate resistivity in GaAs is a result of its larger bandgap. Semi-insulating GaAs material naturally provides de­vice-to-device electrical isolation.

Digital capability in GaAs has passed from the SSI (small-scale integration, ~ 10 gates) realm into the MSI (medium-scale integration, ~ 100 gates), and is headed for LSI (large-scale inte­gration, ~ 1000 gates). Fabrication of an 8 x 8 bit parallel multi­plier (1008 gates fabricated from approximately 6000 transistors and diodes) has been recently reported, which is the most complex GaAs integrated circuit reported to date.

GaAs IC technology is being developed to meet important system needs. Advanced systems are faced with challenges which require significant advances in the rate of real-time signal. An at­tractive objective is to convert analog microwave signals to digital format in a high-speed A/D converter as close as possible to the microwave receiver front, and then to process the data digitally. The bandwidth which can be achieved in GaAs should be capable of permitting digital processing of microwave signals including A/D conversion to become a reality.

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3.26.На основе прочитанных текстов и ваших знаний по специальности подготовьте сообщения на английском языке по следующим темам:

Рис. 4

1. Технология полупроводниковых приборов и интег­ральных схем. 2. Новые материалы и новые технологии в производстве ИС, БИС, СБИС.

3.27. Изучите схему технологических процессов (Рис. 4) и составьте аналогичную схему на английском языке.

3.28. Сравните информацию, изложенную в тексте, со схемой планарного процесса производства кремниевого р-п-р транзистора. Составьте аналогичную схему на англий­ском языке.

3.29. Прочитайте стихотворение Chip Fabrication, на­писанное одним из редакторов журнала IEЕЕ Transactions on Electron Devices. Дайте подстрочный (или стихотвор­ный) перевод.

Chip Fabrication

We use an essential trick

With gallium and arsenic

To make the crystals that we need;

A fabrication line to feed. We heat them up until they fuse,

A pressure cooker's what we use.

We put a perfect crystal in

And then we draw it out again.

And so a bigger crystal grows

For hours and hours and no one knows

Exactly what it's going to be

Until it's finished. It's O.D.

Is constant or approximate.

And some of us can hardly wait

Until to cylinder it's ground

And cut in slices almost round

And polish'd till you see your face.

Of any defects there's no trace.

And now the part the grow­ers hate,

We have to start to fabricate.

We take the slices so pristine

And give them just an extra clean.

We put them into gases pure

And elevate their temper­ature;

Deposit nitride on their face

To stop the loss of any trace

Of arsenic, which if it would go

Would make the concen­tration low.

Now phosphor glass is carefully

Added and patterned so that we

Selectively our ions may place,

Not in the fire, but in their space

Appointed by designers skill

To force the currents to fulfil

The power requirements that's expected

(A slice that don't is soon rejected.)

And now the activation's checked

To show us what we may expect

We put the ohmic contacts down

With royal metals, like a crown

With lots of gold and platinum

And don't forget germa­nium.

Nickel's last and we have heaven

Specifically at minus seven.

We probe the chips to see if we

Have currents that may con­stant be

Within a few percent or so

And if they are, then on we go

To the next step, which is the gate

So small we're forced to speculate

Not whether we have made it tall

But rather if it's there at all.

The gate contains titanium

And gold, of course, and platinum.

The opening for the gate re­cessed,

A treatment, we have found, is best

To make devices that exceed

In yield, in power and in speed.

The wafers now with care we take,

We don't want them to fall and break.

We saw them up to little dice

And everything is looking nice.

We toast success, we raise our cup

We bond them down, then blow them up.

РАЗДЕЛ ЧЕТВЕРТЫЙ

Основной текст: Computer as It Is.

Грамматические явления: Типы обстоятельств. Спосо­бы их выявления в тексте и перевод.

Лексические явления: Контекстуальное значение слов: run, handle, background. Перевод слов с префиксами: extra-, trans-, со-, pre-, post-.