semiconductor refers to a material whose electrical conductivity at room temperature is between a conductor and an insulator. Semiconductors are widely used in radio, television and temperature measurement. Diodes, for example, are devices made of semiconductors. A semiconductor is a material whose electrical conductivity can be controlled, ranging from insulator to conductor. Whether from the perspective of technology or economic development, the importance of semiconductors is very huge. The core units in most of today's electronic products, such as computers, mobile phones or digital recorders, are closely related to semiconductors. Common semiconductor materials are silicon, germanium, gallium arsenide, etc., and silicon is one of the most influential in commercial applications among various semiconductor materials.
There are many semiconductor materials, which can be divided into two categories according to chemical composition: elemental semiconductor and compound semiconductor. Germanium and silicon are the most commonly used elemental semiconductors; Compound semiconductors include Group Ⅲ and Ⅴ compounds (gallium arsenide, gallium phosphide, etc.), Group Ⅱ and Ⅵ compounds (cadmium sulfide, zinc sulfide, etc.), oxides (oxides of manganese, chromium, iron, copper), and solid solutions composed of group ⅲ-ⅴ compounds and group ⅱ-ⅵ compounds (gallium aluminum arsenic, gallium arsenic phosphorus, etc.). In addition to the above crystalline semiconductors, there are amorphous glass semiconductors, organic semiconductors and so on.
The classification of semiconductors, according to its manufacturing technology can be divided into: integrated circuit devices, discrete devices, optoelectronic semiconductors, logic ics, analog ics, storage and other categories, in general, these will be divided into small categories. In addition, there is a classification by application field, design method, etc., although not commonly used, it is still classified according to IC, LSI, VLSI(super LSI) and their scale. In addition, there are methods that can be divided into analog, digital, analog and digital mixture and function according to the signals processed by it.
Intrinsic semiconductor: A semiconductor that does not contain impurities and has no lattice defects is called an intrinsic semiconductor. At very low temperatures, the valence band of the semiconductor is full band (see band theory), after being thermally excited, some electrons in the valence band will cross the forbidden band into the empty band with higher energy, the empty band becomes a conduction band after the presence of electrons in the valence band, and the lack of an electron in the valence band forms a positively charged vacancy, called a hole. Hole conduction is not an actual motion, but an equivalent. When the electron conducts electricity, the hole of equal charge will move in its opposite direction. They produce directional motion under the action of external electric field and form macroscopic current, which are called electron conduction and hole conduction respectively. This type of hybrid conduction due to the generation of electron-hole pairs is called intrinsic conduction. The electrons in the conduction band will fall into the hole, and the electron-hole pair will disappear, which is called recombination. The energy released during recombination becomes electromagnetic radiation (luminescence) or thermal vibration energy (heating) of the lattice. At a certain temperature, the generation and recombination of electron-hole pairs exist at the same time and reach dynamic equilibrium, at which time the semiconductor has a certain carrier density and thus a certain resistivity. When the temperature increases, more electron-hole pairs will be produced, the carrier density will increase, and the resistivity will decrease. Pure semiconductors without lattice defects have high resistivity and few practical applications.
The relationship between semiconductors and integrated circuits:
semiconductor
Semiconductors are materials that guide electrical properties between conductors and insulators. We know that the circuit has a certain function mainly because there are various changes in the current inside it, and the current is formed mainly because there are electrons flowing (movement\/migration) between the metal line and the electronic component. Therefore, the ease with which electrons move through the material determines its conductive properties. Common metal materials are easy to obtain energy for electrons to move at room temperature, so their electrical conductivity is good; Due to the characteristics of the material itself, it is difficult for electrons to obtain the energy required for conducting electricity, and few electrons can migrate within the insulator, so it is almost non-conductive. The conductive properties of semiconductor materials are in between these two, and can be changed by adding impurities to artificially control whether it conducts electricity or not and how easily it conducts electricity. This is called the dopable property of semiconductors.
As mentioned earlier, the basis of the integrated circuit is the transistor, the invention of the transistor is possible to create the integrated circuit, and the basis of the transistor is the semiconductor, so the semiconductor is also the basis of the integrated circuit. Semiconductors are to integrated circuits what land is to cities. Obviously, mountains and hills are not suitable for building cities, and places with sandy soil and limestone are not suitable for building cities. To \"build\" a city, you need to choose a good site, and to \"integrate\" a circuit, you need a suitable base material - semiconductor. Common semiconductor materials are silicon, germanium, gallium arsenide (compounds), of which the most widely used, the most successful commercial push \"silicon\".
So why are semiconductors, and silicon in particular, suitable for making integrated circuits? There are various reasons. After oxygen, silicon is the most abundant element in the Earth's crust. There are a lot of silicates or silica in nature, such as rocks and gravel, which is the reason for the cost of raw materials. The dopable properties of silicon are easy to control, and it is easy to manufacture transistors that meet the requirements, which is the reason for the circuit principle. The silicon dioxide formed by the oxidation of silicon is stable and can be used as an excellent insulating film required in semiconductor devices, which is the reason for the structure of the device. The most critical point is the planar process of integrated circuits, silicon is easier to implement oxidation, lithography, diffusion and other processes, more convenient integration, and its performance is easier to control. Therefore, the following is mainly introduced based on silicon integrated circuit knowledge, silicon transistor and integrated circuit process understanding, it will be easier to understand this problem.
In addition to dopability, semiconductors also have several characteristics such as thermal sensitivity, photosensitivity, negative resistivity temperature, and commutability, so semiconductor materials can be used for power devices, optoelectronic devices, pressure sensors, thermoelectric refrigeration and other purposes in addition to manufacturing large-scale integrated circuits. The use of microelectronic ultrafine processing technology can also be made into MEMS(micro-mechanical electronic system), which is applied in the electronic and medical fields.