What is The Third-generation Semiconductor Industry?

Semiconductor materials can be classified into three generations in chronological order. The first generation consists of common elemental materials such as germanium and silicon, which are characterized by convenient switching and are generally used in integrated circuits. The second-generation compound semiconductors such as gallium arsenide and indium phosphide are mainly used in luminescent and communication materials. The third-generation semiconductors mainly include compound semiconductors such as silicon carbide and gallium nitride, as well as special elements like diamond. With its excellent physical and chemical properties, silicon carbide materials are gradually being applied in the fields of power and radio frequency devices.

The third-generation semiconductors have better withstand voltage and are ideal materials for high-power devices. The third-generation semiconductors mainly consist of silicon carbide and gallium nitride materials. The bandgap width of SiC is 3.2eV, and that of GaN is 3.4eV, which far exceeds the bandgap width of Si at 1.12eV. Because the third-generation semiconductors generally have a wider band gap, they have better voltage resistance and heat resistance, and are often used in high-power devices. Among them, silicon carbide has gradually entered large-scale application. In the field of power devices, silicon carbide diodes and MOSFETs have begun commercial application.

Power devices made with silicon carbide as the substrate have more advantages in performance compared to silicon-based power devices: (1) Stronger high-voltage characteristics. The breakdown electric field strength of silicon carbide is more than ten times that of silicon, which makes the high-voltage resistance of silicon carbide devices significantly higher than that of the same silicon devices. (2) Better high-temperature characteristics. Silicon carbide has a higher thermal conductivity than silicon, making it easier for devices to dissipate heat and allowing for a higher ultimate operating temperature. High-temperature resistance can significantly increase power density while reducing the requirements for the heat dissipation system, making the terminal lighter and smaller. (3) Lower energy loss. Silicon carbide has a saturation electron drift rate twice that of silicon, which makes silicon carbide devices have extremely low on-resistance and low on-loss. Silicon carbide has a bandgap width three times that of silicon, which significantly reduces the leakage current of silicon carbide devices compared to silicon devices, thereby lowering power loss. Silicon carbide devices do not have current tailing during the turn-off process, have low switching losses, and significantly increase the switching frequency in practical applications.

According to relevant data, the on-resistance of silicon carbide-based MOSFETs of the same specification is 1/200 of that of silicon-based MOSFETs, and their size is 1/10 of that of silicon-based MOSFETs. For inverters of the same specification, the total energy loss of the system using silicon carbide-based MOSFETs is less than 1/4 compared to that using silicon-based IGBTs.

According to the differences in electrical properties, silicon carbide substrates can be classified into two types: semi-insulating silicon carbide substrates and conductive silicon carbide substrates. These two types of substrates, after epitaxial growth, are respectively used to manufacture discrete devices such as power devices and radio frequency devices. Among them, semi-insulating silicon carbide substrates are mainly used in the manufacturing of gallium nitride RF devices, optoelectronic devices, etc. By growing gallium nitride epitaxial layers on semi-insulating silicon carbide substrates, silicon carbide-based gallium nitride epitaxial wafers can be fabricated, which can be further made into gallium nitride RF devices such as HEMT. Conductive silicon carbide substrates are mainly used in the manufacture of power devices. Unlike the traditional manufacturing process of silicon power devices, silicon carbide power devices cannot be directly fabricated on silicon carbide substrates. Instead, a silicon carbide epitaxial layer needs to be grown on a conductive substrate to obtain a silicon carbide epitaxial wafer, and then Schottky diodes, MOSFETs, IGBTs and other power devices can be manufactured on the epitaxial layer.