From ultra-high purity silicon wafers with 11 nines to the preparation of 4-inch silicon carbide single crystals, every breakthrough in semiconductor material technology is propelling the information age forward.
The semiconductor industry is the cornerstone of modern technology, and semiconductor materials are the foundation of this cornerstone. From the earliest germanium materials to the current silicon dominance, and now the rise of wide bandgap semiconductor materials, innovations in semiconductor materials have always driven the development of electronic information technology. Based on the evolution of semiconductor materials, they can be divided into three generations: The first generation of semiconductor materials is represented by silicon and germanium, laying the foundation for microelectronics technology; The second generation of semiconductor materials is centered around gallium arsenide and indium phosphide, promoting the development of optoelectronic technology and radio frequency technology; The third generation of semiconductor materials is typified by silicon carbide and gallium nitride, which are helping achieve new breakthroughs in fields such as new energy vehicles and 5G communications.
01 Silicon Materials: The Absolute Mainstay of the Semiconductor Industry
Silicon materials are the most widely used and technologically mature materials in the semiconductor industry, accounting for over 95% of the global semiconductor materials market share. The dominant position of silicon materials stems from their various unique advantages. Silicon has a bandgap of 1.12 eV, with high carrier mobility and good thermal stability, making it the most commonly used semiconductor material today. The abundance of silicon in the earth’s crust, second only to oxygen, results in low raw material acquisition costs. Semiconductor-grade silicon materials need to achieve ultra-high purity of over 99.999999999% (11N), far exceeding the purity requirements of photovoltaic silicon materials at 99.9999% (4-6N). Wafer manufacturing is the core process for the application of silicon materials. With the advancement of Moore’s Law, semiconductor silicon wafers are evolving towards larger sizes. Currently, 300mm (12-inch) silicon wafers have become the market mainstream, with a usable area more than twice that of 200mm wafers, and a utilization rate (the number of chips that can be produced from a unit wafer) approximately 2.5 times that of 200mm wafers. Silicon wafers can be categorized into polished wafers, epitaxial wafers, and SOI (Silicon on Insulator) wafers based on manufacturing processes. Among them, polished wafers can be directly used for semiconductor device manufacturing or serve as substrate materials for epitaxial and SOI silicon wafers.
02 Gallium Arsenide Materials: Leveraging Advantages in Optoelectronic Properties
As a representative of the second generation of semiconductor materials, gallium arsenide possesses excellent electron mobility and saturation velocity, significantly outperforming silicon materials in optoelectronic properties and high-frequency performance. Gallium arsenide has a bandgap of 1.42 eV and a zinc blende structure, exhibiting high electron mobility and good thermal stability. These characteristics give it an irreplaceable position in optoelectronic devices and high-frequency devices. Molecular beam epitaxy (MBE) is an important technology for preparing gallium arsenide nanowires. Research shows that MBE technology can produce gallium arsenide nanowires with a diameter of about 30 nm and lengths ranging from tens to hundreds of nanometers, which have a single crystal structure, belong to the zinc blende structure, and exhibit excellent photoluminescence properties. Gallium arsenide materials show significant mechanical anisotropy on the {100} crystal plane. Its elastic modulus, Poisson’s ratio, and shear modulus exhibit periodic variations, while the shear modulus on the {100} crystal plane is a constant value of 59.4 GPa. This anisotropy arises from differences in structural parameters between different crystal planes.
03 Silicon Carbide and Gallium Nitride: The Rise of Wide Bandgap Materials
The third generation of wide bandgap semiconductor materials, silicon carbide and gallium nitride, exhibit significant advantages in power electronics and radio frequency fields due to their high breakdown electric field, high thermal conductivity, and high-temperature resistance. The bandgap of silicon carbide is much higher than that of silicon, with a high voltage tolerance 10 times that of silicon and thermal conductivity three times that of silicon, making it particularly suitable for high-voltage and high-temperature scenarios such as new energy vehicles and power grid upgrades. Gallium nitride has a bandgap of 3.4 eV, the largest among all semiconductor materials, thus possessing high breakdown voltage and radiation resistance. Gallium nitride materials exhibit excellent high-frequency characteristics, showing great application potential in wireless charging, high-frequency communication, and LED lighting. The market size for silicon carbide and gallium nitride devices is expected to reach billions of dollars by 2025, becoming a new growth point for the semiconductor industry. These materials are driving improvements in energy conversion efficiency and contributing to carbon neutrality goals.
04 Material Preparation Technologies and Process Evolution
The preparation technology of semiconductor materials directly determines the quality of the materials and the performance of the final devices. Currently, mainstream preparation technologies include chemical vapor deposition, molecular beam epitaxy, and physical vapor deposition. Chemical vapor deposition (CVD) can deposit uniform thin films on various substrates, suitable for the growth of silicon wafers, silicon carbide, and other materials. The CVD method has advantages such as fast growth rate, simple process, and low cost. Molecular beam epitaxy (MBE) technology deposits atomic or molecular beams of semiconductor materials onto substrates under ultra-high vacuum conditions to form epitaxial layers. Although MBE has a slow growth rate, complex processes, and high costs, the quality of the produced films is excellent. Wafer preparation is a complex and meticulous process, including crystal rod growth, rod cutting and inspection, outer diameter grinding, slicing, edge rounding, surface grinding, etching, defect removal, polishing, cleaning, inspection, and packaging, among many other steps. Precision control at each step is crucial, directly affecting the quality of the final product.
05 Material Performance Optimization and Characterization Technologies
The optimization of semiconductor material performance is an ongoing process. Through doping, nanostructure design, and interface engineering, significant improvements can be made to the electrical, thermal, and mechanical properties of materials. Doping technology is a key process for regulating the performance of semiconductor materials. By adding specific impurity atoms to pure semiconductor materials, their conductivity type and electrical properties can be altered. N-type doping uses impurities such as phosphorus, arsenic, and antimony, while P-type doping uses impurities such as boron, gallium, and indium. Advanced characterization technologies are fundamental for analyzing material structures and properties. X-ray diffraction (XRD) can be used to analyze crystal structures and lattice constants, scanning electron microscopy (SEM) can observe surface morphology, and photoluminescence spectroscopy can study the optical properties of materials. For gallium arsenide materials, studies have found that their mechanical properties exhibit significant anisotropy. The mechanical performance of gallium arsenide varies significantly along different crystal directions on the {100} crystal plane, with the <110> crystal direction being the most favorable for crack propagation. This finding has important implications for the processing and reliability design of gallium arsenide devices.
06 Future Development Trends of Semiconductor Materials
The field of semiconductor materials is moving towards high performance, environmental friendliness, multifunctionality, and cost reduction. Innovations in new materials and advancements in processes will continue to drive the entire semiconductor industry forward. Two-dimensional materials such as graphene, transition metal dichalcogenides (TMDs), and hexagonal boron nitride (h-BN) have broad application prospects in electronics, energy, and catalysis due to their unique physicochemical properties. These materials are expected to bring revolutionary changes to semiconductor devices. As chip processes continue to approach physical limits, three-dimensional integrated circuits and heterogeneous integration are becoming important development directions. By integrating different types and functions of chips together, system performance and energy efficiency can be significantly enhanced. The Chinese semiconductor materials market is rapidly developing, and it is expected that by 2025, China will become the largest semiconductor materials market in the world. With policy support and market demand driving growth, the technological level and market share of domestic semiconductor materials are expected to continue to improve. In the next five years, the semiconductor materials field will witness more groundbreaking advancements. The market for silicon carbide and gallium nitride power devices is expected to grow at an annual rate of over 30%, while two-dimensional materials are expected to achieve initial commercial applications within 3-5 years. The global semiconductor industry landscape is being reshaped, with Chinese companies transitioning from technology followers to innovation leaders. As the process of localization accelerates, the Chinese semiconductor materials industry is expected to occupy an important position in global competition.
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