Summarize the functions, advantages and methods of MOS large-scale integration

(1) Advantages of large-scale integration

In addition to the general advantages described in section 3.2.1, there are the following advantages. Compared with bipolar transistors, the manufacturing process of MOS transistors is simple, and complex functions can be realized with only the same element. Therefore, the yield of MOS large-scale integrated circuits is high, which is conducive to large-scale integration. Large-scale integration of MOS. Due to the high impedance of the MOS integrated circuit, the three-dimensional cross wiring can be realized without affecting the DC characteristics of the circuit with the help of the pass-through area made at the same time as the source and drain diffusion areas. Therefore, when complex wiring is required, there is no need to use difficult technologies that will affect the yield.

Due to the high impedance, in order to prevent the external stray capacitance from reducing the operating speed in a separate integrated circuit, a buffer can be added, but in a large-scale integrated circuit, it is not necessary to connect a buffer except for the unit circuit connected to the output terminal. , And because the stray capacitance is small, the power consumption required by the unit circuit can be reduced and the speed can be increased.

(2) Large-scale integrated functions

The technical points that should be considered when carrying out large-scale integration are high yield, easy photolithography mask design, and small number of external leads. From the aspects of easy mask design and inspection and small number of external leads, the memory and shift register are realized by repeating the functions constituted by simple unit circuits, so this aspect is firstly integrated on a large scale. Large-scale integration of MOS. In the future, devices with high frequency of use such as adders have been realized. Now, any general circuit can be integrated on a large scale according to user orders, and the integration level can reach the scale of several thousand components.

(3) Large-scale integrated method

Circuits such as memory and shift registers have achieved large-scale integration through efforts in the direction of minimizing the unit circuit area. Regarding the large-scale integration of general circuits, there is a method as follows: a diffusion area for penetration is provided around the unit circuit (gate). Then, according to the requirements of different circuits, the method of arbitrarily wiring the unit circuit 15); using the vertical diffusion area array as the source, drain and pass-through area, and the horizontal metal film array as the gate electrode and wiring, and simply form a large-scale according to the logic diagram. Method of integrated circuit graphics 16); MOS large-scale integration. Several unit circuits are stored in the computer's program library in the form of all possible patterns with little change, and then the logic diagram is converted into a wiring diagram by the computer, and then the automatic drawing method of the large-scale integrated circuit pattern is drawn from the wiring diagram 17) .

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