An integrated circuit that combines a large number of transistors into a single chip

Very Large Scale Integration Circuit (VLSI) is an integrated circuit that combines a large number of transistors into a single chip, and its integration degree is larger than that of a large-scale integrated circuit. The number of integrated transistors differs among different standards. Since the 1970s, with the development of complex semiconductors and communication technologies, the research and development of integrated circuits has gradually begun. The control core microprocessor in the computer is the most typical example of VLSI. VLSI design, especially digital integrated circuits, is usually carried out by means of electronic design automation. It has become an important branch of computer engineering. one.

Very Large Scale Integrated circuits (VLSI)

Integrated circuits that have more than 100,000 elements integrated on one chip, or gate circuits with more than 10,000 gates, are called VLSI circuits. Very large scale integrated circuits were developed in the late 1970s and are mainly used for manufacturing memory and microprocessors. The 64kbit random access memory is the first generation of ultra-large scale integrated circuits, containing approximately 150,000 components with a line width of 3 microns.

The integration degree of VLSI has reached 6 million transistors with a line width of 0.3 micron. Electronic devices manufactured using VLSI circuits are small, light-weight, low-power, and highly reliable. Utilizing VLSI technology, it is possible to "integrate" an electronic subsystem or even an entire electronic system on a single chip to accomplish various functions such as information collection, processing, and storage. For example, the entire 386 microprocessor circuit can be integrated on a single chip with 2.5 million transistors. The successful development of ultra-large-scale integrated circuits is a quantum leap in microelectronics technology, which has greatly promoted the advancement of electronic technology and has led to the development of military and civilian technologies. VLSI has become an important symbol for measuring the level of development of a country's science, technology and industry. It is also the world's major industrial country, especially the United States and Japan, where competition is most intense.

Development status

Billions of transistor-level processors have been used commercially. As semiconductor manufacturing processes jump from the 32-nanometer level to the next 22 nanometers, such integrated circuits will become more common, despite challenges such as process corner deviations. A notable example is Nvidia's GeForce 700 series' first graphics core, code-named 'GK110', which employs a total of 7.1 billion transistors to process digital logic. Most of Itanium's transistors are used to form 32 million bytes of L3 cache. The Intel Core i7 processor has a chip integration level of 1.4 billion transistors. The design used is different from the early ones in that it uses a wide range of electronic design automation tools. Designers can put most of their energy into the hardware description language of the circuit logic functions, and functional verification, logic simulation, logic synthesis, layout, wiring, Layouts, etc. can be done computer-assisted.

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As the scale of technology continues to expand and the complexity of microprocessors continues to increase, microprocessor designers have encountered several challenges.

Power consumption and heat dissipation: With the increase in the scale of component integration, the thermal power generated per unit volume also gradually increases. However, the heat dissipation area of ​​the device does not change and the heat dissipation per unit area does not meet the requirements. At the same time, the static power consumption caused by the weak sub-threshold current of a single transistor becomes increasingly significant due to the large increase in the number of transistors. Some low-power design techniques have been proposed, such as dynamic voltage and frequency scaling (DVFS), to reduce the total power dissipated.

Process deviation: Since lithography is limited by optical laws, more precise doping and etching will become more difficult and the possibility of errors will increase. Designers must perform technical simulations before the chip is manufactured.

Stricter design rules: Due to lithography and etching processes, the design rules for integrated circuit layout must be more stringent. Designers must always consider these rules when designing layouts. The total cost of custom design has reached a critical point, and many design organizations tend to start with electronic design automation to achieve automatic design.

Design Convergence: As the clock frequency of digital electronic applications tends to rise, designers have found it more difficult to keep clock skew low across the entire chip. This sparked interest in multi-core, multi-processor architectures (see Amdahl's Law).

Cost: As the grain size shrinks, the wafer size increases and the number of grains per unit area of ​​the wafer increases, so that the complexity of the photomask used in the manufacturing process increases dramatically. Modern high-precision photomask technology is very expensive.