Dry Process Technology
LSI Technology has been the cutting edge of the innovate semiconductor industry. In the field of the process technology, much effort has been made to improve microfabrication and thinner-film formation technology. In particular, improvements in photolithographic and etching techniques are the keys to the integration of more devices on smaller chips, increases in circuit performance, and improvement in wafer process yield.
Dry etching technology represents a new and exciting method for defining precise images in insulators, semiconductors, and metals. Gas plasma etching technology in dry process like RF sputtering, ion beam milling, reactive ion etching, and reactive ion beam etching is widely used as a fundamental tool for the fabrication of MOS, bipolar LSIs, discrete devices and hard mask. It results in improved image size, simplification of the manufacturing process, precise shape control of fine patterns, and development of a cleaner manufacturing process, compared with conventional wet chemical etching processes.
Recently, MOS LSI has sriifted from LSI phase to VLSI phase, which requires a precise pattern less than 3 µm. This transition can be achieved by progress in wafer process technology, including microfabrication as well as device and circuits design technologies. Conventional plasma etching is not adequate in VLSI regions for the delineation of precise patterns because of its inherent undercutting (подтравливающий) effect which results in anisotropic profile of an etched pattern.
Dry etch technologies available for LSI processing are classified into plasma etch, sputter etch and ion beam etch, with items such as etch mode, apparatus and reaction mechanism.
Определите контекстуальное значение выделенных слов.
3.22. Переведите, обращая внимание на контекстуальное значение слов due to, appear, advance:
1. The numerical value of the conductivity changes due to the concentration of impurities. 2. The significance a semiconductor achieved is due to the electrons being raised to the conduction band. 3. Current due to holes injected into the collector from the base can be neglected since it is very small. 4. New design tools and development systems are appearing. 5. The limiting point appears to be between 10 and 30 Ohms. 6. Recent technological advances in software development are now opening new horizons. 7. The advances made by device fabrication have allowed all functions to be integrated onto just one chip.
3.23. Выявите контекстуальное значение выделенных слов без словаря:
1. More efficient communication demands a continually increasing level of control in progressively-thinner layers. 2. The extension of any semiconductor technology to small dimensions brings with it a host of new technology, physics and engineering challenges.
Учитесь говорить.
3.24. Подготовьте 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.
3.25. Докажите правильность или ошибочность следующих высказываний. При доказательстве используйте следующие выражения:
I'm not sure that...; the drawback to the (...) is that it is not useful for...; it requires a complex procedure...; it is expensive....
1. Plasma technology is presently in wide-spread use in the semiconductor technology. 2. Molecular electronics is the most forward-looking of several modern approaches to the development of small, reliable, efficient electronic systems.
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.
Учитесь говорить.
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.