Introduction to Semiconductor
Definition and classification
Semiconductor is a kind of material between conductor and insulator, and its conductivity increases with the increase of temperature. According to their internal carrier types, semiconductors can be divided into two categories: Positive semiconductor and Negative semiconductor. In P-type semiconductors, the majority carriers are electron holes, while in N-type semiconductors, the majority carriers are electrons.
The Importance of Semiconductors
The discovery and application of semiconductors have completely changed modern science and technology and daily life. They are the core of modern electronic devices, such as smart phones, computers, medical devices and so on. Because semiconductors can be highly integrated in tiny sizes, they make devices smaller and lighter, and at the same time more powerful and energy efficient. In addition, compared with traditional conductor materials, semiconductors have obvious advantages in power, efficiency and cost.
Historical background
The research on semiconductors began in the early 20th century, but it was not until 1947, when scientists at Bell Laboratories invented the first transistor, Semiconductor technology It really began to get wide attention and application. Since then, with the invention of integrated circuits and the progress of microelectronics technology, the semiconductor industry has experienced explosive growth, which has spawned a series of technological revolutions and industrial changes.
In the history of semiconductor development, there are many milestone events and inventions, such as the wide application of silicon, the development of CMOS technology, and the emergence of nanoscale technology. These technologies and events together promote the progress of semiconductor technology and make it an indispensable part of modern society.
Fundamentals of Semiconductor Physics
Band theory
Energy band theory is the basis of explaining the conductivity of solid materials. In solids, atoms are so close that their electron clouds overlap to form energy bands. According to Pauli's incompatibility principle, each energy level can only have two electrons at most, thus forming a continuous energy band. The lowest band is called the valence band, and the band immediately above it is called the conduction band. The energy gap between conduction band and valence band is called band gap.
P-type and N-type semiconductors
P-type semiconductor: When a trivalent element such as boron (B) is doped into a semiconductor, holes are formed in the lattice. These holes can accept electrons and make semiconductors positively charged, so they are called P-type semiconductors.
N-type semiconductor: When a pentavalent element such as phosphorus (P) is doped into a semiconductor, more electrons are added to the lattice. These extra electrons make semiconductors negative, so they are called N-type semiconductors.
Carrier and doping
Carriers refer to electrons or holes involved in conduction in semiconductors. In N-type semiconductors, redundant electrons are the main carriers, while in P-type semiconductors, holes are the main carriers. Doping is a technique that changes the conductivity of pure semiconductor materials by adding trace amounts of other elements to them. Doping can increase the conductivity of semiconductors, reduce their manufacturing costs and improve their efficiency.
Electrical properties of semiconductors
The electrical properties of semiconductors mainly depend on the concentration and type of carriers in them. For example, the conductivity of N-type semiconductors is mainly determined by electrons, while the conductivity of P-type semiconductors is mainly determined by holes. In addition, the conductivity of semiconductors is also affected by temperature, illumination and external electric field. In a certain temperature range, the conductivity of semiconductors increases with the increase of temperature. In addition, when a semiconductor is illuminated, it will produce electron-hole pairs, thus enhancing its conductivity.
Semiconductor Materials and Manufacturing
Common Semiconductor material
Silicon (Si): Silicon is the most commonly used semiconductor material, mainly because of its richness and excellent electrical properties. Silicon has a band gap of 1.1 eV, which is suitable for most electronic applications.
Germanium (Ge): Germanium is the first semiconductor material to be discovered, but it is less used now because of its small band gap (0.66 eV) and its performance at high temperature is inferior to that of silicon.
Compound semiconductor: Such as gallium nitride (GaN), gallium arsenide (GaAs) and cadmium telluride (CdTe). These materials usually have a larger band gap than silicon, so they perform better in some specific applications, such as LED and solar cells.
Semiconductor manufacturing process
Semiconductor fabrication process is a complex multi-step process, including oxidation, lithography, etching, ion implantation and chemical vapor deposition. Among them, lithography is a key step in the manufacturing process, which uses photomask and photoresist to form tiny patterns on silicon wafers.
Semiconductor wafer manufacturing
Wafer fabrication begins with the growth of silicon ingots, and then cuts them into thin sheets, which are called wafers. These wafers are washed, oxidized and otherwise processed several times to prepare surfaces for subsequent processes. Subsequently, tiny electronic devices are formed on the wafer by photolithography, etching and other processes.
Packaging and testing
After the wafer is manufactured, it needs to be packaged to protect it from the external environment. In the packaging process, the wafer is fixed on a supporting structure and then connected with external circuits. After packaging, perform functional and performance tests to ensure that each device meets the specifications.
In the semiconductor manufacturing process, cost control, efficiency improvement and quality assurance are the key points. With the development of technology, the dimensions and specifications of devices are shrinking, which requires more precise and precise manufacturing process.
Semiconductor Devices and Applications
Diodes and transistors
Diode: Diodes are the simplest semiconductor devices that allow current to flow in only one direction. Because of its unidirectional conductivity, diodes are often used in rectifier circuits to convert alternating current into direct current. LED (Light Emitting Diode) is a special type of diode that can emit light.
Transistor: Transistors are the core of semiconductor technology. They can be used as amplifiers or switches. According to its structure and working principle, transistors can be divided into bipolar transistors (BJT) and field effect transistors (FET). The invention of transistor laid the foundation for the emergence of integrated circuit and the rapid development of microelectronics technology.
Integrated circuit (IC)
An integrated circuit is a complex circuit consisting of several to hundreds of millions of transistors, integrated on a small silicon wafer. With the development of technology, the size of IC has been shrinking, the performance has been improving, but the cost has been greatly reduced. This trend is called Moore's Law.
Memory device
The storage device is used for storing and retrieving data. According to its working principle and application, memory devices can be divided into random access memory (RAM) and read only memory (ROM). Among them, RAM use for temporary storage, while ROM is permanent storage.
Application of Semiconductor in Various Industries
Semiconductor technology has been widely used in various industries, such as:
Communication: Used for mobile phones, routers and other communication devices.
Calculation: Applications in personal computers, servers, and supercomputers.
Consumer electronics: Such as TV, stereo and game console.
Medical treatment: Used in medical imaging and biosensors.
Traffic: Used for control and navigation in cars, airplanes and trains.
The progress of semiconductor technology not only improves the performance of these devices, but also reduces their cost and power consumption, thus bringing great convenience to people's daily life and work.
Overview of semiconductor industry
Status quo of world semiconductor market
Semiconductor industry is one of the largest and fastest growing industries in the world. With the progress of technology and the increasing demand for high-performance computing, cloud computing, Internet of Things and artificial intelligence, the semiconductor market continues to grow. Although the market is huge, it is also affected by cyclical fluctuations, which are closely related to the global economic situation and technological innovation.
Major semiconductor enterprises and brands
Intel: The world's largest semiconductor manufacturer, mainly producing microprocessors and memory devices.
Samsung: In addition to being the world's largest mobile phone manufacturer, it is also a major manufacturer of memory and display devices.
TSMC: The largest independent semiconductor foundry in the world, producing chips for many chip design companies.
NVIDIA: Mainly produces graphics processors, and has also entered the artificial intelligence and data center market in recent years.
AMD: Intel's main competitor, producing microprocessors and graphics processors.
Industry Chain and Ecology
The chain of semiconductor industry includes material supply, chip design, manufacturing, packaging, testing and application. Specialized companies participate in every link, forming a complex ecosystem. For example, material suppliers provide necessary silicon, chemicals and other materials; The design company is responsible for the chip design; The foundry is responsible for production; The packaging and testing company is responsible for the follow-up processing and quality inspection.
In addition, with the progress of technology, the semiconductor industry is also facing continuous innovation and change. With the emergence of new manufacturing processes, new materials and new technologies, the performance of chips is continuously improved, the power consumption is reduced, and the cost is gradually reduced.
Future Trends of Semiconductors
Technology development trend
As Moore's Law approaches, Semiconductor industry is facing a technical bottleneck. However, new technologies and methods, such as 3D integration, new materials and quantum computing, provide new opportunities for the future development of the industry.
Three-dimensional integration: Traditional planar integrated circuits are limited by physical size, while three-dimensional integration technology provides higher integration and performance by vertically stacking multiple circuit layers.
New material: Traditional silicon-based semiconductors may not meet future needs, and new materials such as graphene and topological insulators may become alternatives.
Quantum computation: Quantum computation utilizes the principles of quantum mechanics and provides higher computational power than traditional computation, especially in some specific problems.
Exploration of new materials and new technologies
In order to break through the technical bottleneck, the industry is actively exploring new materials and technologies. For example, new materials such as gallium nitride and graphene, due to their superior electrical properties, are regarded as possible substitutes for silicon.
Applications of Semiconductors in Emerging Fields
With the progress of technology, semiconductors are also entering new application fields:
Artificial intelligence: High-performance computing and deep learning require a lot of computing power, which provides great opportunities for the semiconductor industry.
Biotechnology: Semiconductor technology has a wide range of applications in gene sequencing, biosensors and medical imaging.
Energy and Environment: Semiconductors also have important applications in solar cells, energy storage and environmental monitoring.
Start from scratch: A guide to the basics of semiconductors-China Sea Semiconductor (exportsemi.com)
