14.3 Прочитай и письменно переведи текст optical lithography:

Optical lithography has undisputably been the leading integrat­ed circuit pattern defining technique for many years. It has essen­tially two steps. First, the design and fabrication of the optical mask, which is both costly and time consuming, and secondly, the expo­sure of the wafer, covered with a layer of light sensitive photoresist to ultraviolet light shone through the mask. The method is ideal for large scale production because once the expensive maskmaking pro­cess has been carried out, an unlimited number of wafers may be patterned at very low cost to the producer. On the other hand, where specific or semicustom (полузаказные) ICs are concerned this pro­cess has proved unacceptable since the cost and time involved in mask fabrication cannot be justified by the production of only a few devices which may require several interactions for optimum results. For these reasons, electron beam direct-write lithography is prov­ing invaluable in the field of application of specific or semicustom integrated circuits. This technique allows fast turnaround, a high flexibility and comparatively low cost for very small batches. In ad­dition, the short wavelength of electron-beam offers very high res­olution patterning and so may be essential where sub-micron fea­tures are required. Despite the possibility of low throughout, e-beam generated patterns allow either simple wafer-scale integration or devices for several customers, each possibly with a variety of trial designs to be implemented on a single wafer. The major advantage of the e-beam’s high resolution capability will be nullified if the resist pattern cannot be very precisely reproduced onto the metalli­zation layer. For this reason, wet-etching of the metal with its in­herent undercutting is particularly unsuitable and plasma-process­ing becomes necessary. Reactive ion etching is a type of plasma etching where the wafer is placed on an electrode which is capacitively coupled to an RF generator. A second electrode larger than this driven one is grounded and a plasma is generated by electronic excitation of a low pressure gas contained between them. The ar­rangement of the system is such that the driven electrode experi­ences a negative bias with respect to the plasma causing positive ions to be accelerated towards the wafer. This means that not only is there chemical reaction causing removal of the metallization but also ion-enhanced chemical etching and physical sputtering to the vertical etching essential for precise replication of the resist pat­tern. Dry processing has the added benefits of easily handled pro­cess materials, easy automation and good reproducibility.

14.4 Подготовь и сделай сообщения по следующим темам:

1. Film technology and semiconductor technology.

2. Silicon for microelectronics.

3. Oxidation and its function.

4. The techniques for the deposition of thin films.

14.5 Прочитай и письменно переведи текст III—V SEMICONDUCTOR INTEGRATED CIRCUITS и используя рисунок, опиши принцип действия прибора. На основе про­читанного и твоих знаний по специальности подготовь сообщения о: а) техноло­гии полупроводниковых приборов и ИС; б) новых материалах и новой технологии производства ИС, БИС и СБИС.

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 III—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 on the picture.

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 e V is necessary to pro­vide the proper photon energy, 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 «-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 mm.

The first integration of GaAs M ESFET 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 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 IС 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. At 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.

PASSIVE VOICE

The Passive употребляется для выражения:

• действия, которое было совершено неизвестным, неважным или ясным из контекста лицом: Mrs. Archer’s ruby ring was stolen from her house last night.

• действия более важного, чем лицо, совершающее действие. в обзорах новостей, статьях, официальных записях, инструкций, рекламы: Two teenagers were seriously injured in a car accident last night.

• более вежливого высказывания: My new blouse is ruined. Вместо: You’ve ruined my blouse.

В Passive обычно не употребляются The Present Perfect Continuous, The Future Continuous, The Past Perfect Continuous и The Future Perfect Continuous.

В разговорной речи часто заменяют to be на to get: Mary got run over by a car while she was crossing the street.

Present Simple	am/is/are v3	Future Simple	will be v3
Present Continuous	am/is/are being v3	Future Perfect	will have been v3
Past Simple	was/were v3	Present Infinitive	(to) be v3
Past Continuous	was/were being v3	Perfect infinitive	(to) have v3
Present Perfect	have/has been v3	Continuous Infinitive	being v3
Past Perfect	had been v3	Modals	modal be v3

Для изменения предложения из active в passive:

• дополнение становится подлежащим

• сказуемое остается в том же времени

• перед дополнение в passive (бывшее подлежащее active) ставится by или оно опускается

• если за сказуемым стоит дополнение предложение может быть изменено в passive: Peter feeds the cows. –> The cows are fed by Peter.

• by + дополнение употребляется, чтобы сказать кто или что совершает действие. With + инструмент/ материал/ ингредиент: A kite was made by John. It was made with paper, paint & string.

• если подлежащее в passive: people, one, someone, somebody, they, he, etc., дополнение обычно опускается: People eat a lot of junk food nowadays. -> A lot of junk food is eaten nowadays.

• дополнения me, you, him, etc. в active становятся подлежащими I, you, he, etc. в passive: They rescued me. -> I was rescued.

• с глаголами bring, tell, send, show, teach, promise, buy, throw, write, award, hand, sell, owe, grant, allow, feed, pass, post, read, take, offer, give, pay и lend можно сделать два разных предложения в passive: Jessica showed Rod some photos. -> Rod was shown some photos by Jessica.(этот вариант предпочтительнее)/Some photos were shown to Rod by Jessica.

• если в active за сказуемым следует предлог, то в passive он сохраняется: Jane looks after the baby. -> The baby is looked after by Jane.

• вопросы в passive строятся по схеме Who/What … by?: Who was the camera invented by? What was the explosion caused by?

С глаголами think, believe, say, report, know, expect, consider, understand, etc. можно личные и безличные формы в passive:

Active	Passive безличный	Passive личный
People say that he has lost his job.	It is said he has lost his job.	He is said to have lost his job.
People know that she works hard.	It is known she works hard.	She is known to work hard.
People think he left the country last night.	It is thought he left the country last night.	He is thought to have left the country last night.

Конструкция have something done используется, чтобы сказать, что кто-то что-то делает для нас: Sandra is having her car repaired at the moment.

• Вопросы и отрицания образуются при помощи do/does/did: Do you have your hair cut every month? Did she have the house cleaned?

• Have something done используется чтобы сказать, что произошло что-то неприятное: Mary had her purse stolen yesterday.

Get можно употреблять вместо have в неформальном общении: We must get the fridge repaired soon.