Very Large Scale Integration Circuit (VLSI)transistorCombined into a single chipIntegrated circuit, its integration degree is greater thanlarge-scale integrated circuit。The number of integrated transistors varies in different standards.Since the 1970s, with the development of complexsemiconductoras well ascommunications technologyThe research and development of integrated circuits are also gradually launched.Control core in computermicroprocessorIt is the most typical example of VLSI design, especiallyDigital integrated circuit, which is usually carried out by means of electronic design automation, has become one of the important branches of computer engineering.
In the 1920s, some inventors tried to master the method of controlling the current in solid-state diodesBipolar transistorIs realized in.However, their assumption is that untilthe Second World WarIt can only be realized after the end.During the war, people focused on manufacturing military products such as radars, so the development of electronic industry was not as rapid as that of later. However, people's understanding of semiconductor physics gradually increased, and the level of manufacturing technology also gradually improved.After the war, many scientists began to engage in the research of solid-state electronic devices again.In 1947, the famous Bell Laboratory successfully developed the transistor.Since then, the research direction of electronics has shifted from vacuum tubes to solid-state electronic devices.
At that time, transistors seemed to be small and efficient.In the 1950s, some electronic engineers hoped to develop more advanced and complex circuits based on transistors.However, with the increase of circuit complexity, the impact of technical problems on device performance has gradually attracted people's attention.
imageComputer motherboardSuch a complex circuit often requires high response speed.If the components of the computer are too large, or the wires between different components are too long,electrical signalIt will not be able to spread fast enough in the circuit, which will cause the computer to work slowly, inefficient, and even cause logic errors.
In 1958,Texas InstrumentsJack Kilby found the solution to the above problem.He proposed that all components and chips in a circuit can be made of the same semiconductor material block.At that time, his colleagues were on vacation. When they finished their vacation, Kilby immediately showed his new design.Later, he developed a test version of this new circuit.In September 1958, the first integrated circuit was successfully developed.Although this integrated circuit looks very rough and has some problems, it is indeed an innovative concept in the history of electronics.By integrating all components on the same material block and connecting each part through the upper metallization layer, separate independent components are no longer needed, thus avoiding the steps of manually assembling components and wires.In addition, the characteristic size of the circuit is greatly reduced.With the gradual development of electronic design automation, many processes in the manufacturing process can be realizedAutomatic control。Since then, the idea of integrating all components into a single silicon chip has been realized. The era of Small Scale Integration (SSI) began in the early 1960s, and later went through Medium Scale Integration (MSI, late 1960), large-scale integrated circuits and very large-scale integrated circuits (early 1980).The number of transistors in VLSI can reach 10000.
Small scale integrated circuitAppeared in 1960silicon waferIt contains 10-100 elements or 1-10 logic gates.Such as logic gates and triggers.If small-scale digital integrated circuit (SSI) is used for designCombinational logic circuitThe gate circuit is taken as the basic unit of the circuit, soLogical functionThe simplification of should make the minimum number of gate circuits used and the minimum number of gate inputs.
If selectedMedium scale integrated circuit(MSI) DesignCombinational logic circuitThe number and variety of integrated circuits used are the least, and the connections between integrated circuits are the least.This often requires transforming the logic function expression into the expression required by the selected circuit, sometimes directly using the standard normal form.
Although the functions of MSI medium scale combined logic devices are better thanSmall scale integrated circuitSSI is strong, but it is not as functional as LSI. Although there are many varieties of these device products, they cannot fully meet the user's requirements. This requires that multiple chips be cascaded to expand their functions, and some standard medium scale inheritance components can also be used to implement the design of other combined logic circuits.When using medium scale integrated components to design combinational logic circuits, the method is to select a suitable MSI, and then transform the logic expression of the actual problem into the expression of the response MSI.Compared with the combinational logic circuit designed with gate circuit, the combinational logic circuit designed with MSI not only has small volume and light weight, but also improves the working reliability.
Cascade selected from medium scale data can expand the number of selected data paths, and its function expansion can not only be used forCombinational logic circuitAnd can also be used forSequential logic circuit。The main applications in combinational logic circuits are as follows:
(1) Cascade expansion to increase the number of selected routes and bits, which can realize data transmission from multiple bits to multiple bits;
(2) It is used as a logic function generator to realize the design of arbitrary combination logic circuits.
Large Scale Integrated circuits (LSI)
It appeared in 1970 and contains 103-105 elements or 100-10000 logic gates on a silicon chip.For example:Semiconductor memory, some computer peripherals.628512628128 (128K) maximum capacity 1G.
Very Large Scale Integrated circuits (VLSI)
An integrated circuit with more than 100000 components or more than 10000 gates integrated on a chip is called a VLSI.VLSI was successfully developed in the late 1970s and is mainly used to manufacture memories and microprocessors.64k bitRandom access memoryIt is the first generation ultra large scale integrated circuit, which contains about 150000 components and has a line width of 3 microns.
The integration degree of VLSI has reached 6 million transistors, and the line width has reached 0.3 μ m.The electronic equipment manufactured by VLSI is small in size, light in weight, low in power consumption and high in reliability.Using VLSI technology, an electronic subsystem or even the entire electronic system can be "integrated" on a chip to complete information acquisition, processing, storage and other functions.For example, the entire 386 microprocessor circuit can be integrated on a single chip with 2.5 million transistors.The successful development of VLSI isMicroelectronicsThis is a leap forward, which has greatly promoted the progress of electronic technology, thus driving the development of military technology and civil technology.VLSI has become an important symbol to measure the level of science and technology and industrial development of a country, and it is also a field with the most intense competition among major industrial countries in the world, especially the United States and Japan.
Ultra Large Scale Integration (ULSI)
In 1993, with the successful development of 16M FLASH and 256M DRAM integrated with 10 million transistors, we entered the era of ULSI (Ultra Large Scale Integration).The number of integrated components of VLSI is between 107 and 109.
The rapid growth of ULSI circuit integration mainly depends on the following two factors:Crystal growth technologyHas reached a very high level;The second is the continuous improvement of manufacturing equipment, and the improvement of processing accuracy, automation and reliability has made the device size enter the deep submicron field.The silicon single crystal preparation technology can make the radial parameters of the crystal uniform, reduce the micro defects in the body, and the defects with the size of 0.1~0.3um can be less than 0.05 per square centimeter on average.We also have a relatively complete understanding of the theoretical model of defects induced in the process of circuit processing, thus developing a complete set of crystal processing technology.The continuous increase in the diameter of silicon wafers used for circuit production has led to a significant increase in production efficiency. The diameter of silicon wafers has reached 12 inches.The reduction of micro defects increases the yield of chips. The yield of 256MB DRAM can reach 80~90% with 0.02 defects per square centimeter.
Giga Scale Integration (GSI)
In 1994, the successful development of 1G DRAM integrating 100 million components entered the era of Giga Scale Integration (GSI).hugelarge-scale integrated circuitThe number of integrated components is more than 109.[1]
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By late 2012, billions of transistor processors had been commercially available.As the semiconductor manufacturing process leaps from the 32nm level to the next 22nm level, this kind of integrated circuit will become more common, although challenges such as process angle deviation will be encountered.Notable example is the first of Nvidia's GeForce 700 seriesShow Core, code 'GK110'Graphics ProcessorAll 7.1 billion transistors are used to process digital logic.Most of Itanium's transistors are used to form its 32 million byte three-level cache.The chip integration of Intel Core i7 processor has reached 1.4 billion transistors.The design adopted is different from the early ones in that it widely uses electronic design automation tools. Designers can focus most of their efforts on the hardware description language expression form of circuit logic functions, while function verification, logic simulation, logic synthesis, layout, wiring, layout, etc. can be completed by computer assistance.[2]
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Due to the continuous expansion of technology scale and the increasing complexity of microprocessors, the designers of microprocessors have encountered several challenges.
1 Power consumption and heat dissipation: With the increase of component integration scale, the thermal power generated per unit volume gradually increases, however, the heat dissipation per unit area does not meet the requirements due to the constant heat dissipation area of the device.At the same time, a single transistor is weakSubthreshold currentThe resulting static power consumption becomes increasingly significant due to the substantial increase in the number of transistors.Some low-power design techniques, such as dynamic voltage and frequency scaling (DVFS), have been proposed to reduce the total power dissipation.
2. Process deviation: Since photolithography technology is limited by optical laws, higher precision doping and etching will become more difficult, and the possibility of causing errors will become greater.The designer must carry out technical simulation before chip manufacturing.
3 Stricter design rules: Due to the problems of photolithography and etching process, the design rules of integrated circuit layout must be more strict.When designing the layout, the designer must always consider these rules.The total cost of custom design has reached a critical point, and many design organizations tend to start from electronic design automation to achieve automatic design.
4 Design convergence: As the clock frequency of digital electronic applications tends to rise, designers find it more difficult to maintain a low clock offset on the entire chip.This has aroused interest in multi-core, multiprocessor architectures (see Amdar's Law).
5 Cost: As the grain size shrinks, the wafer size becomes larger, and the number of grains per unit wafer area increases, the complexity of photomask used in the manufacturing process rises sharply.Modern high-precision photomask technology is very expensive.
manufacturer
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"Super large scale" was said many years ago.The most advanced manufacturing process has reached the order of magnitude of 7nm, and the actual mass production process is mostly 14nm and 22nm.In terms of sales, the top three companies are Intel (the United States), Samsung (South Korea) and TSMC (Taiwan).Other companies are mostly European, American, Japanese and Taiwan companies.Only SMIC International in mainland China can keep up with the trend of technological development.
