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Integrated circuit


Integrated circuit
Microelectronics - the most significant and, as many believe, the most important scientific and technological advances of our time. Compare it can be such a turning point in the history of art as the invention of printing in the XVI century, the creation of the steam engine in the XVIII century and electrical engineering development in the XIX. And today when it comes to the scientific and technological revolution, the first thing we have in mind is microelectronics. Like no other technical advance of the day, it permeates all spheres of life and makes the reality is that yesterday was simply impossible to imagine. To see this, it suffices to recall about pocket calculators, mini radios, electronic control devices in home appliances, watches, computers and programmable computer. And this is only a small part of its field of application!

His appearance and the very existence of microelectronics obliged to create a new super small electronic element - integrated circuit. The appearance of these schemes, in fact, there was some fundamentally new invention - it stems directly from the logic of the development of semiconductor devices. Initially, when only the semiconductor elements included in the life of each transistor, a resistor or a diode used alone, that is consisted of a body and the individual included in the circuit by means of their individual contacts. This was done even in cases when it was necessary to collect a lot of similar schemes from the same elements. But gradually it came to the realization that such devices are not rationally assembled from separate elements, and immediately produce the same general crystal, the more that the semiconductor electronics has created all the prerequisites for this. In fact, all the semiconductor elements on the device is very similar to each other, they have the same principle and differ only interposition pn areas. These pn region, as we recall, are of the same type by introducing impurities into the surface layer of the semiconductor crystal. Moreover, reliable and from all points of view, satisfactory performance of the overwhelming majority of semiconductor devices is provided by the thickness of the surface of the working layer in thousandths of a millimeter. In the smallest transistors usually used only the upper layer of the semiconductor crystal is only 1% of its thickness. The remaining 99% act as a carrier or support, as without the substrate transistor just could crumble at the slightest touch. Therefore, using the technology used for the manufacture of certain electronic components, you can immediately create a single chip a complete circuit of several tens, hundreds or even thousands of such components. The benefits of this will be enormous. Firstly, immediately decrease the cost (the cost of the chip is typically hundreds of times smaller than the aggregate value of all the electronic components of its components). Secondly, such a device will be much more reliable (as experience shows, in the thousands and tens of thousands of times), and it is of paramount importance, since finding a fault in the circuit of the tens or hundreds of thousands of electronic components is transformed into an extremely complex problem. Third, due to the fact that all the electronic components of integrated circuits in hundreds or thousands of times smaller than their counterparts in a conventional modular scheme, power consumption is much less, and the speed - is much higher.

The key event, heralded the arrival of integralizatsii in electronics, was the proposal of the American engineer John. Kilby of «Texas Instruments» firms receive equivalent elements for the entire scheme, such as registers, capacitors, transistors and diodes in a monolithic piece of pure silicon. The first semiconductor integrated circuit Kilby created in the summer of 1958 year. And already in 1961, the company «Fairchild Semiconductor Corporation» has released the first production of computer chips: a coincidence circuit, polusdvigayuschy register and trigger. In the same year the production of semiconductor integrated logic circuits mastered firm «Texas». The following year, there were integrated circuits others. In a short time the different types of amplifiers were created in the integral version. In 1962, the firm RCA has developed integrated memory arrays chips for computer memory devices. Gradually release chipset has been launched in all countries - microelectronics era began.

The starting material for integrated circuits is typically untreated plate made of pure silicon. It has a relatively large size, since it is produced at the same time, several hundreds of similar chips. The first operation consists in the fact that by oxygen at a temperature of 1000 degrees on the surface of this plate forming a layer of silicon dioxide. silicon oxide and characterized by high chemical resistance and mechanical properties has a wonderful insulator, providing reliable isolation of the underlying silicon. The next step - the introduction of the impurities to create zones of p or n conduction. For this purpose, the oxide film is removed from the places of the plate, which correspond to the individual electronic components. Selecting the right areas is done by a process known as photolithography. First, the entire oxide layer is coated photosensitive composition (photoresist), which plays the role of photographic film - it lights up and can be exercised. Thereafter, through a special photomask containing a pattern of the semiconductor crystal plate illuminated with ultraviolet rays. When exposed to light the flat pattern is formed on the oxide layer, and the non-illuminated areas are bright, and all the rest - tinted. At the point where the photoresistor exposed to light, the insoluble portions are formed of film, resistant to acid. The plate was then treated with a solvent that removes photoresist from the illuminated areas. With places opened (and only them) a layer of silicon oxide is etched with acid. As a result, in the right places silica dissolves and opens "windows" pure silicon, ready for the introduction of impurities (ligation). To this substrate surface at a temperature of 900-1200 degrees exposed to the desired impurity, such as phosphorus or arsenic, for obtaining n-type conduction. Impurity atoms penetrate into the depths of pure silicon, but repelled by its oxide. After processing one type impurities plate, it is prepared for ligation other type - the surface of the plate again covered with a layer of oxide is carried out a new photolithography and etching, whereby the new open "windows" silicon. Following ligation, it should be new, for example with boron to obtain p-type conductivity. Since the entire crystal surface formed at the proper locations p and n region. (Insulation between the individual elements can be created in several ways: such exclusion can serve as a layer of silicon oxide, can also be created in the right places the locking pn junctions.) The next stage of treatment is associated with the application of conductive compounds (conductive lines) between elements of the integrated circuit, as well as between the elements and contacts for connection to external circuits. To this end, the substrate is sprayed a thin layer of aluminum, which is deposited as a thin film. Its photolithographic process and subjected to etching, similar to those described above. As a result of all of the metal layer remains only a thin conductive lines and pads. In conclusion, the entire surface of the semiconductor chip covered with a protective layer (usually silica glass), which is then removed from the pads. All chips produced are subjected to strict inspection to control test bench. Faulty circuits are marked with a red dot. Finally, the crystal is cut into individual plate-chips, each of which is a solid body with leads for connection to external circuits.

The complexity of the integrated circuit characterized by an indicator, called the degree of integration. Integrated circuits with more than 100 elements, called chips with a low degree of integration; circuits comprising elements 1000 - integrated circuits with average degree of integration; scheme of up to tens of thousands of elements - large integrated circuits. Already made circuits containing up to a million cells (called extra-large). The gradual increase of integration has led to the fact that the circuit is getting more and more miniaturized and accordingly more complex. A huge number of electronic devices that had previously large dimensions, is now fit on a tiny silicon wafer. An extremely important event in this direction was the creation in 1971 of the American company "Intel" single integrated circuit for performing arithmetic and logical operations - the microprocessor. This led to a great breakthrough in the field of microelectronics computing.

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