incorporated, design, technologies, invention, printed circuit boards, inexpensive, bipolar junction transistor, reliability, advantages, contained, doping.

2. Bipolar integrated circuits are the circuits in which the principal element is the ….

3. Several major types of MOS device fabrication … have been developed since the mid-1960s.

4. These miniature circuits have demonstrated low cost, high …, low power requirements, and high processing speeds compared to the vacuum tubes and transistors which preceded them.

5. After the … of the IC in 1959, the number of components and circuits that could be … into a single chip doubled every year for several years.

6. The complex and interconnected design of the circuits and components is prepared in a process similar to that used to make ….

7. Integrated circuit microcomputers are so … they are even found in children’s electronic toys.

8. The uncovered areas are then either chemically etched to open up a layer or are subjected to chemical … to create a layer of P or N regions.

10. They allowed more complex systems to be produced using smaller circuit boards, less assembly work (because of fewer separate components), and a number of other ….

6. Read the text and arrange the following items of outline in accordance with the text.

An integrated circuit, commonly referred to as IC, is a microscopic array of electronic circuits and components that has been diffused or implanted onto the surface of a single crystal, or chip, of semiconducting material such as silicon. It is called an integrated circuit because the components, circuits, and base material are all made together, or integrated, out of a single piece of silicon, as opposed to a discrete circuit in which the components are made separately from different materials and assembled later. ICs range in complexity from simple logic modules and amplifiers to complete microcomputers containing millions of elements.

The first integrated circuits were created in the late 1950s in response to a demand from the military for miniaturized electronics to be used in missile control systems. At the time, transistors and printed circuit boards were the state-of-the-art electronic technology. Although transistors made many new electronic applications possible, engineers were still unable to make a small enough package for the large number of components and circuits required in complex devices like sophisticated control systems and handheld programmable calculators. Several companies were in competition to produce a breakthrough in miniaturized electronics, and their development efforts were so close that there is some question as to which company actually produced the first IC. In fact, when the integrated circuit was finally patented in 1959, the patent was awarded jointly to two individuals working separately at two different companies.

After the invention of the IC in 1959, the number of components and circuits that could be incorporated into a single chip doubled every year for several years. The first integrated circuits contained only up to a dozen components. The process that produced these early ICs was known as small scale integration, or SSI. By the mid-1960s, medium scale integration, MSI, produced ICs with hundreds of components. This was followed by large scale integration techniques, or LSI, which produced ICs with thousands of components and made the first microcomputers possible.

The first microcomputer chip, often called a microprocessor, was developed by Intel Corporation in 1969. It went into commercial production in 1971 as the Intel 4004. Intel introduced their 8088 chip in 1979, followed by the Intel 80286, 80386, and 80486. In the late 1980s and early 1990s, the designations 286, 386, and 486 were well known to computer users as reflecting increasing levels of computing power and speed. Intel’s Pentium chip is the latest in this series and reflects an even higher level.

Only a half century after their development was initiated, integrated circuits have become ubiquitous. Computers, cellular phones, and other digital appliances are now inextricable parts of the structure of modern society. That is, modern computing, communications, manufacturing and transport systems, including the Internet, all depend on the existence of integrated circuits.

The impact of integrated circuits on our lives has been enormous. ICs have become the principal components of almost all electronic devices. These miniature circuits have demonstrated low cost, high reliability, low power requirements, and high processing speeds compared to the vacuum tubes and transistors which preceded them. Integrated circuit microcomputers are now used as controllers in equipment such as machine tools, vehicle operating systems, and other applications where hydraulic, pneumatic, or mechanical controls were previously used. Because IC microcomputers are smaller and more versatile than previous control mechanisms, they allow the equipment to respond to a wider range of input and produce a wider range of output. They can also be reprogrammed without having to redesign the control circuitry. Integrated circuit microcomputers are so inexpensive they are even found in children’s electronic toys.

a) It is a circuit consisting of a great number of components mounted one after another on a silicon wafer.

b) It is a circuit consisting of a number of vacuum tubes and transistors placed on chip.

c) It is a circuit containing a great number of components made of semiconductor materials diffused or implanted on the surface of a silicon wafer.

b) Their invention caused rapid increase in the performance of electronic equipment.

c) They did not allow the equipment to respond to a wider range of input and produce wider range of output.

a) They are cheap, reliable, consume much power and are characterized by lower processing speed.

b) They are reliable, cheaper, consume less power and handle more information than vacuum tubes.

a) The first integrated circuit appeared in the result of efforts to meet the requirement of the military sphere for electronics designed for missile control systems.

b) They were needed because sophisticated control systems and handheld programmable calculators contained smaller number of components and were less complex.

c) Transistors and printed circuit boards were too small to be used in the electronics for missile control systems.

5. What was the rate of the IC’s complexity increase in the years that followed its invention?

c) Each successive type had higher computing power and speed thanks to the higher power of its processor.

1. Integrated circuit is a circuit consisting of a few discrete transistors placed on wafer.

3. The first integrated circuit appeared in the result of efforts to provide electronic devices for sophisticated missile control systems.

5. For several decades after the IC invention, the number of components on a single chip remained unchanged.

6. MSI circuits were followed by LSI circuits consisting of hundreds of components.

9. Pick up the information from the text that might be of use to speak about the evolution of integrated circuits. Find additional information in the WWW.

11. The text is divided into several parts. Look through the text and arrange the titles of the parts in accordance with the text.

1. Hundreds of integrated circuits are made at the same time on a single, thin slice of silicon and are then cut apart into individual IC chips. The manufacturing process takes place in a tightly controlled environment known as a clean room where the air is filtered to remove foreign particles. The few equipment operators in the room wear lint-free garments, gloves, and coverings for their heads and feet. Since some IC components are sensitive to certain frequencies of light, even the light sources are filtered. Although manufacturing processes may vary depending on the integrated circuit being made, the following process is typical.

2. The actual IC manufacturing is preceded by the stage of preparing the silicon waver. The procedure includes the conversion of silicon into monocrystal form and creation of monocrystalline silicon ingot. Then, a thin, round wafer of silicon is cut off the ingot using a precise cutting machine called a wafer slicer. Each slice is about 0.01 to 0.025 inches (0.004 to 0.01 cm) thick. The surface on which the integrated circuits are to be formed is polished. Once the wafer is formed and processed the actual IC manufacturing begins.

3. It starts with the oxide film coating of the wafer. The surfaces of the wafer are coated with a layer of silicon dioxide to form an insulating base and to prevent any oxidation of the silicon which would cause impurities. The silicon dioxide is formed by subjecting the wafer to superheated steam at about 1000°C under several atmospheres of pressure to allow the oxygen in the water vapor to react with the silicon. Controlling the temperature and length of exposure controls the thickness of the silicon dioxide layer.

4. The complex and interconnected design of the circuits and components is prepared in a process similar to that used to make printed circuit boards. For ICs, however, the dimensions are much smaller and there are many layers superimposed on top of each other. The design of each layer is prepared on a computer-aided drafting machine, and the image is made into a mask which will be optically reduced and transferred to the surface of the wafer. The mask is opaque in certain areas and clear in others. It has the images for all of the several hundred integrated circuits to be formed on the wafer.

A drop of photoresist material is placed in the center of the silicon wafer, and the wafer is spun rapidly to distribute the photoresist over the entire surface. The photoresist is then baked to remove the solvent.

The coated wafer is then placed under the first layer mask and irradiated with light. Because the spaces between circuits and components are so small, ultraviolet light with a very short wavelength is used to squeeze through the tiny clear areas on the mask. Beams of electrons or x-rays are also sometimes used to irradiate the photoresist.

The mask is removed and portions of the photoresist are dissolved. If a positive photoresist was used, then the areas that were irradiated will be dissolved. If a negative photoresist was used, then the areas that were irradiated will remain. The uncovered areas are then either chemically etched to open up a layer or are subjected to chemical doping to create a layer of P or N regions.

5. One method of adding dopants to create a layer of P or N regions is atomic diffusion. In this method a batch of wafers is placed in an oven made of a quartz tube surrounded by a heating element. The wafers are heated to an operating temperature of about 1500-2200°F (816-1205°C), and the dopant chemical is carried in on an inert gas. As the dopant and gas pass over the wafers, the dopant is deposited on the hot surfaces left exposed by the masking process. This method is good for doping relatively large areas, but is not accurate for smaller areas. There are also some problems with the repeated use of high temperatures as successive layers are added.

The second method to add dopants is ion implantation. In this method a dopant gas, like phosphine or boron trichloride, is ionized to provide a beam of high-energy dopant ions which are fired at specific regions of the wafer. The ions penetrate the wafer and remain implanted. The depth of penetration can be controlled by altering the beam energy, and the amount of dopant can be controlled by altering the beam current and time of exposure. Schematically, the whole process resembles firing a beam in a bent cathode-ray tube. This method is so precise, it does not require masking ‑ it just points and shoots the dopant where it is needed. However it is much slower than the atomic diffusion process.

6. The process of masking and etching or doping is repeated for each successive layer depending on the doping process used until all of the integrated circuit chips are complete. Sometimes a layer of silicon dioxide is laid down to provide an insulator between layers or components. This is done through a process known as chemical vapor deposition, in which the wafer’s surface is heated to about 752°F (400°C), and a reaction between the gases silane and oxygen deposits a layer of silicon dioxide. A final silicon dioxide layer seals the surface, a final etching opens up contact points, and a layer of aluminum is deposited to make the contact pads. At this point, the individual ICs are tested for electrical function.

7. The thin wafer is like a piece of glass. The hundreds of individual chips are separated with a fine diamond cutter and then putting the wafer under stress to cause each chip to separate. Those ICs that failed the electrical test are discarded. Inspection under a microscope reveals other ICs that were damaged by the separation process, and these are also discarded.

8. The good ICs are individually bonded into their mounting package and the thin wire leads are connected by either ultrasonic bonding or thermocompression. The mounting package is marked with identifying part numbers and other information.

The completed integrated circuits are sealed in anti-static plastic bags to be stored or shipped to the end user.

13. Read part 5 and say what methods of doping are described in it. Say what weak points of each method of doping are mentioned.

14. What kind of process is used to provide an insulator between layers or components?

15. Say whether it is right to state that ICs are qualified as good or to be discarded only by microscope inspection.

16. Make your own block diagram of the IC manufacturing process and be ready to give details concerning some of the stages (e.g. photoresist coating, masking, doping).

Depending on the type of transistors the integrated circuits are based on they can be classified into bipolar, MOS¹ and BiCMOS² integrated circuits.

Bipolar integrated circuits are the circuits in which the principal element is the bipolar junction transistor. They are generally used where the highest logic speed is desired.

The other major class of integrated circuits is called MOS because its principal device is a metal oxide semiconductor field-effect transistor (MOSFET³). It is more suitable for very large-scale integration (VLS⁴) than bipolar circuits because MOS transistors are self-isolating and can have an average size of less than 10⁻⁷ in.⁻² (10⁻⁵ mm²). This has made it practical to use millions of transistors per circuit. Because of this high-density capability, MOS transistors are used for high-density random-access memories (RAMs⁵), read-only memories (ROMs⁶), and microprocessors.

Several major types of MOS device fabrication technologies have been developed since the mid-1960s. They are: (1) metal-gate p -channel MOS (PMOS⁷), which uses aluminum for electrodes and interconnections; (2) silicon-gate p -channel MOS, employing polycrystalline silicon for gate electrodes and the first interconnection layer; (3) n -channel MOS (NMOS), which is usually silicon gate; and (4) complementary MOS (CMOS⁸), which employs both p -channel and n -channel devices.

Both conceptually and structurally the MOS transistor is a much simpler device than the bipolar transistor. In fact, its principle of operation has been known since the late 1930s, and the research effort that led to the discovery of the bipolar transistor was originally aimed at developing the MOS transistor. What kept this simple device from commercial utilization until 1964 is the fact that it depends on the properties of the semiconductor surface for its operation, while the bipolar transistor depends principally on the bulk properties of the semiconductor crystal. Hence MOS transistors became practical only when understanding and control of the properties of the oxidized silicon surface had been perfected to a very great degree

There is a strong interest in combining high-performance bipolar transistors and high-density CMOS transistors on the same chip (BiCMOS). This concept originated with work on bipolar circuits when power limitations became important as more functionality (and thus more transistors) was added to the chip. It is possible to continue adding more circuits on a chip without increasing the power by combining the low-power CMOS circuits with the bipolar circuits. This is done with both memory circuits and logic circuits, resulting in speeds somewhere between those of typical CMOS and bipolar-only circuits, but with the functional density of CMOS. The disadvantage of BiCMOS is its additional cost over plain CMOS or bipolar circuits, because the number of processing steps increases 20–30%. However, this increased complexity is expected to be used when either the additional functionality over bipolar circuits or the increased speed over CMOS circuits justifies the cost.

¹MOS – metal-oxide semiconductor – металл-окисел-полупроводник, МОП-технология (структура);

²BiCMOS – bipolar complementary metal-oxide-semiconductor – (запоминающая) биполярная КМОП-структура; биполярная КМОП-технология, БиКМОП технологический процесс изготовления полупроводниковых устройств;

³MOSFET – metal-oxide semiconductor transistor; metal-oxide semiconductor field-effect transistor – полевой транзистор с МОП-структурой;

⁴VLSI – Very Large-Scale Integration – сверхбольшая степень интеграции, сверхбольшая интегральная микросхема, СБИС;

⁵RAM – random-access memory – запоминающее устройство с произвольной выборкой, оперативное запоминающее устройство;

⁶ROM – read-only memory – постоянное запоминающее устройство;

⁷PMOS – p-channel metal-oxide-semiconductor – МОП-структура с каналом р-типа, р-канальная МОП-структура, р-МОП-структура;

⁸CMOS – Complementary Metal-Oxide Semiconductor, Complementary MOS – комплементарная структура.

1. Make up English-Russian pairs of the words and word-combinations equivalent in meaning.

2. Define the following words as parts of speech and give the initial words of the following derivatives.

Conductivity, insulators, investigation, replacement, inexpensive, manufacturer, application, purifying, improvement, impressive, valuable, unrealible.

1. The rapid growth of the national telephone network had made the … (replace) of mechanical switches highly desirable.

2. It was … (expensive) portable radios that created the first large … (commerce) market for the device.

3. American researchers and … (manufacture) sought the ways to use germanium-based transistors in computing machines.

4. … (improve) in semiconductor devices led to faster, cheaper electronics of all kinds.

6. Silicon has earned a most … (value) place in the history of technology and twentieth-century culture.

4. Read the following words in each line and define their roots. Translate the words into Russian:

Semiconductors are solid materials with a level of electrical conductivity between that of insulators and conductors. Although the scientific study of semiconductors began in the nineteenth century, concentrated investigation of their use did not begin until the 1930s. The development of quantum physics during the first third of the twentieth century gave scientists the theoretical tools necessary to understand the behavior of atoms in solids, including semiconductors. But it was a commercial need that really stimulated semiconductor research in the United States. The rapid growth of the national telephone network had by 1930 made the replacement of mechanical switches highly desirable. Vacuum tubes, used in radios and other devices, were too expensive and fragile for use in the telephone network, so researchers turned their focus to solid crystals. Germanium and silicon showed the most promise. Scientists at Bell Laboratories designed the first transistor using the semiconductor germanium. A prototype was produced in 1947, and innovation followed rapidly.

Transistors replaced vacuum tubes in electronic devices slowly at first. It was inexpensive portable radios that created the first large commercial market for the device. American researchers and manufacturers sought ways to use germanium-based transistors in computing machines. The more versatile silicon, however, ultimately replaced germanium to satisfy the needs of evolving computer technology.

The semiconductor silicon gave its name to a region ‑ an area between San Jose and San Francisco, California, that became known as Silicon Valley ‑ and fomented revolutions in technology, business, and culture. Once scientists had determined that silicon had the necessary properties for applications in computing, practical concerns took center stage. Although silicon is one of the most common elements on earth ‑ sand is made of silicon and oxygen ‑ isolating and purifying it is notoriously difficult. But interest in silicon-based devices was very strong, and by the late 1950s a diversified semiconductor industry was developing, centered in California but serving government and commercial clients throughout the country.

The electronics industry initially turned to semiconducting materials to replace large, slow, electromechanical switches and fragile, unreliable vacuum tubes. But the new technology proved to be far more than an incremental improvement. Semiconductors showed promise for miniaturization and acceleration that previously seemed fanciful. An insatiable desire for faster, smaller devices became the driving force for the semiconductor industry. An impressive stream of innovations in theory, design, and manufacturing led the semiconductor industry to make ever-smaller, ever-faster devices for the next half century. Improvements in semiconductor devices led to faster, cheaper electronics of all kinds, and to the spread of the semiconductor and its dependent industries throughout the world.

The future will likely bring a replacement for silicon in the ongoing search for smaller, faster electronic devices, but silicon has earned a most valuable place in the history of technology and twentieth-century culture.

2. What gave scientists the theoretical tools to understand the behaviour of atoms in semiconductors?

3. Scientists had determined that silicon had the necessary properties for applications in …

9. Read the following statements and say whether they are true or false. Correct the false ones.

1. The concentrated investigation of the use of semiconductors began only in the 1930s.

6. Semiconductors turned out to be promising for miniaturization and acceleration.

11. Using information of the text speak about the role of silicon in the development of the semiconductor industry.

14. Read the text and write key words and phrases revealing the contents of the text.

Until the 1950s, all active electronic functions were performed by the vacuum valve. They were made up of metal electrodes arranged in a vacuum glass envelope. Their sizes varied, but even one of the latest valves had a volume of more than one cubic centimetre. When solid state devices were invented, one of their main attractions was their small size. As the technology developed, individual elements became smaller and smaller, until complete circuits could be designed on a single piece of silicon. This development resulted in the replacement of vacuum valves by transistors in receivers and low-power electronic systems. In high power transmitters vacuum valves continue to and thermionic emitters are still used where a free source of electrons is required as in cathode-ray tubes. But semiconductor devices proved to be poorly equipped to survive certain environments.

For example, when semiconductor devices are exposed to ionizing radiation in space and defence systems, they are bombarded by both neutral and charged particles, which cause fluctuations in current leading to failure of the device. Vacuum tubes are far more immune to such environments. Vacuum tubes work at much higher voltages than semiconductors and they have the potential to provide high frequency operation. Therefore some research centres have developed research programmes for producing micron-sized vacuum electronic devices. It is the semiconductor fabrication technology which now offers the opportunity of producing vacuum tubes as small as transistors.

There are many potential applications of vacuum microelectronics, but they all centre on the properties of field emitting devices. For many years a great deal of effort has been directed towards finding a cold electron source to replace the thermionic cathode in such devices as cathode ray tubes and traveling wave tubes. Most research programmes have concentrated on cold cathodes to take advantage of the small device size, low power consumption and high current densities which in rum will lead to high operating frequencies and fast switching.

18. Find the paragraph in the text which describes one of the main attractions of solid state devices.

19. Explain why most research programmes have concentrated on cold cathodes as a source of electrons.

21. Name advantages vacuum tubes have over solid state devices when they operate in certain environments.

22. Express your attitude to the facts given in the text. You may use the following phrases:

24. Look through the following text, define the information presented in it and entitle the text.

The property of semiconductors that makes them most useful for constructing electronic devices is that their conductivity may easily be modified by introducing impurities into their crystal lattice. The process of adding controlled impurities to a semiconductor is known as doping. The amount of impurity, or dopant, added to an intrinsic (pure) semiconductor varies its level of conductivity. Doped semiconductors are often referred to as extrinsic. By adding impurity to pure semiconductors, the electrical conductivity may be varied not only by the number of impurity atoms but also, by the type of impurity atom and the changes may be thousand folds and million folds.

The materials chosen as suitable dopants depend on the atomic properties of both the dopant and the material to be doped. In general, dopants that produce the desired controlled changes are classified as either electron acceptors or donors. A donor atom that activates (that is, becomes incorporated into the crystal lattice) donates weakly-bound valence electrons to the material, creating excess negative charge carriers. These weakly-bound electrons can move about in the crystal lattice relatively freely and can facilitate conduction in the presence of an electric field. Conversely, an activated acceptor produces a hole. Semiconductors doped with donor impurities are called n-type, while those doped with acceptor impurities are known as p-type. The n and p type designations indicate which charge carrier acts as the material’s majority carrier. The opposite carrier is called the minority carrier, which exists due to thermal excitation at a much lower concentration compared to the majority carrier.

- what makes semiconductors the most useful for constructing electronic devices;

Nanoparticles can have the same dimensions as some biological molecules and can interact with these. In humans and in other living organisms, they may move inside the body, reach the blood and organs such as the liver or the heart, and may also cross cell membranes. Insoluble nanoparticles are a greater health concern because they can persist in the body for long periods of time.

The parameters of nanoparticles that are relevant for health effects are nanoparticle size (smaller particles can be more dangerous), chemical composition and surface characteristics, and shape.

Inhaled nanoparticles can deposit in the lungs and then potentially move to other organs such as the brain, the liver, and the spleen, and possibly the foetus in pregnant women. Some materials could become toxic if they are inhaled in the form of nanoparticles. Inhaled nanoparticles may cause lung inflammation and heart problems.

The objective of nanoparticles used as drug carriers is to deliver more of the drug to the target cells, to reduce the harmful effects of the drug itself on other organs, or both. However, it is sometimes difficult to distinguish the toxicity of the drug from that of the nanoparticle.

With the exception of airborne particles reaching the lungs, information on the behaviour of nanoparticles in the body is still minimal. Assessment of the health implications of nanoparticles should take into account the fact that age, respiratory tract problems, and the presence of other pollutants can modify some of the health effects.

Information on the effects of nanoparticles on the environment is very scarce. However, it is likely that many conclusions drawn from human studies can be extrapolated to other species, but more research is needed.

Information security means protecting information and information systems from unauthorized access, use, disclosure, disruption, modification or destruction. The terms information security, computer security and information assurance are frequently incorrectly used interchangeably. These fields are interrelated often and share the common goals of protecting the confidentiality, integrity and availability of information; however, there are some subtle differences between them. These differences lie primarily in the approach to the subject, the methodologies used, and the areas of concentration. Information security is concerned with the confidentiality, integrity and availability of data regardless of the form the data may take: electronic, print, or other forms. Computer security can focus on ensuring the availability and correct operation of a computer system without concern for the information stored or processed by the computer. Governments, military, corporations, financial institutions, hospitals, and private businesses amass a great deal of confidential information about their employees, customers, products, research, and financial status. Most of this information is now collected, processed and stored on electronic computers and transmitted across networks to other computers. Should confidential information about a business’ customers or finances or new product line fall into the hands of a competitor, such a breach of security could lead to lost business, law suits or even bankruptcy of the business. Protecting confidential information is a business requirement, and in many cases also an ethical and legal requirement. For the individual, information security has a significant effect on privacy, which is viewed very differently in different cultures. The field of information security has grown and evolved significantly in recent years. As a career choice there are many ways of gaining entry into the field. It offers many areas for specialization including: securing network(s) and allied infrastructure, securing applications and databases, security testing, information systems auditing, business continuity planning and digital forensics science, to name a few.

1. Read the title of the following text. Make your predictions about the contents of the text.

An important aspect of information security and risk management is recognizing the value of information and defining appropriate procedures and protection requirements for the information. Not all information is equal and so not all information requires the same degree of protection. This requires information to be assigned a security classification.

The first step in information classification is to identify a member of senior management as the owner of the particular information to be classified. Next, develop a classification policy. The policy should describe the different classification labels, define the criteria for information to be assigned a particular label, and list the required security controls for each classification.

Some factors that influence which classification information should be assigned include how much value that information has to the organization, how old the information is and whether or not the information has become obsolete. Laws and other regulatory requirements are also important considerations when classifying information.

The type of information security classification labels selected and used will depend on the nature of the organisation, with examples being:

- In the business sector, labels such as: Public, Sensitive, Private, Confidential.

- In the government sector, labels such as: Unclassified, Sensitive But Unclassified, Restricted, Confidential, Secret, Top Secret and their non-English equivalents.

- In cross-sectoral formations, the Traffic Light Protocol, which consists of: White, Green, Amber and Red.

All employees in the organization, as well as business partners, must be trained on the classification schema and understand the required security controls and handling procedures for each classification. The classification a particular information asset has been assigned should be reviewed periodically to ensure the classification is still appropriate for the information and to ensure the security controls required by the classification are in place.

2. What kind of solution in the production of integrated circuits was found by Jack kilby?

With the small and effective transistor at their hands, electrical engineers of the 50s saw the possibilities of constructing far more advanced circuits than before. However, as the complexity of the circuits grew, problems started arising.

When building a circuit, it is very important that all connections are intact. If not, the electrical current will be stopped on its way through the circuit, making the circuit fail. Before the integrated circuit, assembly workers had to construct circuits by hand, soldering each component in place and connecting them with metal wires. Engineers soon realized that manually assembling the vast number of tiny components needed in, for example, a computer would be impossible, especially without generating a single faulty connection.

Another problem was the size of the circuits. A complex circuit, like a computer, was dependent on speed. If the components of the computer were too large or the wires interconnecting them too long, the electric signals couldn’t travel fast enough through the circuit, thus making the computer too slow to be effective.

So there was a problem of numbers. Advanced circuits contained so many components and connections that they were virtually impossible to build. This problem was known as the tyranny of numbers.

In the summer of 1958 Jack Kilby at Texas Instruments found a solution to this problem. He was newly employed and had been set to work on a project to build smaller electrical circuits. However, the path that Texas Instruments had chosen for its miniaturization project didn’t seem to be the right one to Kilby.

Because he was newly employed, Kilby had no vacation like the rest of the staff. Working alone in the lab, he saw an opportunity to find a solution of his own to the miniaturization problem. Kilby’s idea was to make all the components and the chip out of the same block (monolith) of semiconductor material. When the rest of the workers returned from vacation, Kilby presented his new idea to his superiors. He was allowed to build a test version of his circuit. In September 1958, he had his first integrated circuit ready. It was tested and it worked perfectly!

Although the first integrated circuit was pretty crude and had some problems, the idea was groundbreaking. By making all the parts out of the same block of material and adding the metal needed to connect them as a layer on top of it, there was no more need for individual discrete components. No more wires and components had to be assembled manually. The circuits could be made smaller and the manufacturing process could be automated.

Jack Kilby is probably most famous for his invention of the integrated circuit, for which he received the Nobel Prize in Physics in the year 2000. After his success with the integrated circuit Kilby stayed with Texas Instruments and, among other things, he led the team that invented the hand-held calculator.

2. What is the difference between printed circuit boards and integrated circuits?

3. Explain the difference between two methods of connecting the components of PCBs?

A printed circuit board, or PCB¹, is a self-contained module of interconnected electronic components found in devices ranging from common beepers, or pagers, and radios to sophisticated radar and computer systems. The circuits are formed by a thin layer of conducting material deposited, or “printed,” on the surface of an insulating board known as the substrate. Individual electronic components are placed on the surface of the substrate and soldered to the interconnecting circuits. Contact fingers along one or more edges of the substrate act as connectors to other PCBs or to external electrical devices such as on-off switches. A printed circuit board may have circuits that perform a single function, such as a signal amplifier, or multiple functions.

There are three major types of printed circuit board construction: single-sided, double-sided, and multi-layered. Single-sided boards have the components on one side of the substrate. When the number of components becomes too much for a single-sided board, a double-sided board may be used. Electrical connections between the circuits on each side are made by drilling holes through the substrate in appropriate locations and plating the inside of the holes with a conducting material. The third type, a multi-layered board, has a substrate made up of layers of printed circuits separated by layers of insulation. The components on the surface connect through plated holes drilled down to the appropriate circuit layer. This greatly simplifies the circuit pattern.

Components on a printed circuit board are electrically connected to the circuits by two different methods: the older “through hole technology” and the newer “surface mount technology”. With through hole technology, each component has thin wires, or leads, which are pushed through small holes in the substrate and soldered to connection pads in the circuits on the opposite side. Gravity and friction between the leads and the sides of the holes keeps the components in place until they are soldered. With surface mount technology, stubby J-shaped or L-shaped legs on each component contact the printed circuits directly. A solder paste consisting of glue, flux, and solder are applied at the point of contact to hold the components in place until the solder is melted, or “reflowed”, in an oven to make the final connection. Although surface mount technology requires greater care in the placement of the components, it eliminates the time-consuming drilling process and the space-consuming connection pads inherent with through hole technology. Both technologies are used today.

Two other types of circuit assemblies are related to the printed circuit board. An integrated circuit, sometimes called an IC² or microchip, performs similar functions to a printed circuit board except the IC contains many more circuits and components that are electrochemically “grown” in place on the surface of a very small chip of silicon. A hybrid circuit, as the name implies, looks like a printed circuit board, but contains some components that are grown onto the surface of the substrate rather than being placed on the surface and soldered.

Integrated circuits were made possible by experimental discoveries which showed that semiconductor devices could perform the functions of vacuum tubes, and by mid-20th-century technology advancements in semiconductor device fabrication. The integration of large numbers of tiny transistors into a small chip was an enormous improvement over the manual assembly of circuits using discrete electronic components. The integrated circuit’s mass production capability, reliability, and building-block approach to circuit design ensured the rapid adoption of standardized ICs in place of designs using discrete transistors.

There are two main advantages of ICs over discrete circuits: cost and performance. Cost is low because the chips, with all their components, are printed as a unit by photolithography and not constructed one transistor at a time. Furthermore, much less material is used to construct a circuit as a packaged IC die than as a discrete circuit. Performance is high since the components switch quickly and consume little power (compared to their discrete counterparts) because the components are small and close together. As of 2006, chip areas range from a few square millimeters to around 350 mm², with up to 1 million transistors per mm².

The idea of an integrated circuit was conceived by a radar scientist working for the Royal Radar Establishment of the British Ministry of Defence, Geoffrey W.A. Dummer (1909-2002), who published it at the Symposium on Progress in Quality Electronic Components in Washington, D.C. on May 7, 1952. He gave many symposia publicly to propagate his ideas.

The integrated circuit can be credited as being invented by both Jack Kilby of Texas Instruments and Robert Noyce of Fairchild Semiconductor working independently of each other. Kilby recorded his initial ideas concerning the integrated circuit in July 1958 and successfully demonstrated the first working integrated circuit on September 12, 1958. In his patent application of February 6, 1959, Kilby described his new device as “a body of semiconductor material... wherein all the components of the electronic circuit are completely integrated”.

Kilby won the 2000 Nobel Prize in Physics for his part of the invention of the integrated circuit. Robert Noyce also came up with his own idea of integrated circuit, half a year later than Kilby. Noyce’s chip had solved many practical problems that the microchip developed by Kilby had not. Noyce’s chip, made at Fairchild, was made of silicon, whereas Kilby’s chip was made of germanium.

A computer virus is a computer program that can copy itself and infect a computer without permission or knowledge of the user. However, the term “virus” is commonly used, albeit erroneously, to refer to many different types of malware programs. The original virus may modify the copies, or the copies may modify themselves, as occurs in a metamorphic virus. A virus can only spread from one computer to another when its host is taken to the uninfected computer, for instance by a user sending it over a network or the Internet, or by carrying it on a removable medium such as a floppy disk, CD, or USB drive. Meanwhile viruses can spread to other computers by infecting files on a network file system or a file system that is accessed by another computer. Viruses are sometimes confused with computer worms and Trojan horses. A worm can spread itself to other computers without needing to be transferred as part of a host, and a Trojan horse is a file that appears harmless. Both worms and Trojans will cause harm to computers when executed. Most personal computers are now connected to the Internet and to local area networks, facilitating the spread of malicious code. Today’s viruses may also take advantage of network services such as the World Wide Web, e-mail, Instant Messaging and file sharing systems to spread, blurring the line between viruses and worms. Furthermore, some sources use an alternative terminology in which a virus is any form of self-replicating malware. Some viruses are programmed to damage the computer by damaging programs, deleting files, or reformatting the hard disk. Others are not designed to do any damage, but simply replicate themselves and perhaps make their presence known by presenting text, video, or audio messages. Even these benign viruses can create problems for the computer user. They typically take up computer memory used by legitimate programs. As a result, they often cause erratic behavior and can result in system crashes. In addition, many viruses are bug-ridden, and these bugs may lead to system crashes and data loss.

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