GaAs mesfeTs Research

More than 40 years have passed since the bipolar transistor was invented by Shockley in 1948. Bipolar technology has highly matured today, and the structure of Si bipolar transistor has been improved almost to its physical limits. The upper frequency limit of its practical application is considered to be 4 GHz regardless of advances in technology.

In 1966, С.A.Mead demonstrated the possibility of a transistor with a very high cut-off frequency employing a GaAs field effect transistor with a Schottky barrier gate. Since then, GaAs MESFET research and development efforts have been made in many laboratories around the world. The main purpose of the de­velopment of GaAs MESFET is to obtain three-terminal mi­crowave semiconductor devices which can be used to develop mi­crowave amplifiers to replace the parametric low noise amplifiers and the travelling wave tube power amplifiers.

In the last several years, GaAs MESFETs have made remark­able progress in both low noise GaAs MESFET amplifiers, re­sulting in a substantial reduction in the cost of microwave com­munication systems. High power GaAs MESFETs replaced some TWTs, guaranteeing a much longer lifetime and a smaller size than the TWT.

Текст 2.8. Прочитайте текст. Какую новую информа­цию вы узнали об использовании материалов? Значения выделенных слов вы сможете понять из контекста.

Materials for Multilayer Interconnections

As device dimensions are becoming increasingly smaller se­vere requirements are being imposed on the electrode material. The basic demand is conductivity because it can substantially im­prove the resistances and delay times of the electrical interconnec­tions lines used for VLIC structures.

Historically, metals like aluminum and gold have been used in bipolar and MOS IC's. With the advent of silicon-gate MOS tech­nology, polysilicon has been extensively used to form gate elec­trodes and interconnections. Refractory metals such as tungsten (W), molybdenum (Mo), titanium (Ti), and tantalum (Та) and their silicides are receiving increased attention as a replace­ment/compliment of polysilicon.

Silicides of W, Mo and Та have reasonably good compatibility with the IC fabrication technology. They have fairly high conduc­tivity, they can withstand all of the chemicals normally encoun­tered during the fabrication process.

Определите контекстуальное значение выделенных слов.

2.21. Переведите, обращая внимание на контекстуаль­ное значение выделенных слов:

1) 1. Aluminum is the most problematic material to be used for metallization in maintaining contact stability. 2. A lower re­sistivity is required for maintaining circuit performance. 3. Use of this self-test technique greatly simplifies field maintenance. 4. For storage and retrieval of data in the bubble-memory use is made of a group of registers and counters for accurately maintaining the position of data. 5. Any system must be designed to require less maintenance. 6. Preventive maintenance is necessary.

2) 1. This entails turning one of the file processors into an in­put/output unit. 2. Today, plants depend on carbon dioxide and water to survive. In turn, they produce organic matter. 3. Water can turn to a solid. 4. Let us now turn to ceramics. 5. At the turn of the 18th century nobody knew of semiconductors.

3) 1. Sometimes the performance of the circuits can suffer from technological advancement. 2. The systematic approach can anticipate the problems that will arise in future VLSI. 3. The av­erage wire length can be estimated by a very useful statistical formula.

Проверьте, знаете ли вы следующие термины.

2.22. Назовите данные термины по-английски. Вы мо­жете найти эти термины в Основном тексте:

1. интегральный усилитель, усилитель считывания, по­лупроводниковый усилитель, усилитель на ПЗС; 2. клей­кое покрытие, проводящее покрытие, нанесение покрытия методом погружения, покрытие, нанесенное напылением, связующий подслой; 3. проектирование кристалла, блоч­ная конструкция, проектирование схемы, топологическое проектирование, оперативное проектирование схем, проек­тирование с выбором схем; 4. акцепторная примесь, леги­рующая примесь, примесь, наносимая на поверхность по­лупроводника; 5. усиление по току, инверсный коэффици­ент усиления, нагрузочная способность логической ИС, номинальный коэффициент усиления; 6. зазор между кон­тактами, ширина запрещенной зоны, запрещенная зона с прямыми переходами, микрозазор, запирающий слой, гер­метизирующий слой, слой, стойкий к травлению, напы­ленный слой, исходный слой, многослойная пленка

Учитесь говорить.

Текст 2.9. Прочитайте текст и кратко изложите его со­держание на английском языке. Используйте следующие выражения:

1. As you can see from the title the text is devoted to...; 2. The problem arose...; 3. According to the text...; 4. Experiments paved the way to ...; 5. Experiments proved ...; 6. Research has shown that...; 7. I find the text rather/very...; 8. I've learnt a lot...