|Silicon carbide industry chain map

The silicon carbide industry chain is mainly composed of substrates, epitaxy, devices, and applications. Silicon carbide wafers, as semiconductor substrate materials, can be divided into conductive type and semi-insulating type according to different resistivity. Conductive substrates can be used to grow silicon carbide epitaxial wafers to make high temperature and high voltage resistant silicon carbide diodes, silicon carbide MOSFETs and other power devices, which are used in new energy vehicles, photovoltaic power generation, rail transit, smart grid, aerospace and other fields ; Semi-insulating substrates can be used to grow GaN epitaxial wafers to make microwave RF devices such as HEMTs that are resistant to high temperature and high frequency, and are mainly used in 5G communications, satellites, radar and other fields.

|Silicon carbide industry chain map

|Production process and cycle

The silicon carbide production process mainly involves the following processes:

1) Single crystal growth, using high-purity silicon powder and high-purity carbon powder as raw materials to form silicon carbide crystals; 2) In the substrate process, silicon carbide crystals are processed to form single crystal flakes through cutting, grinding, polishing, cleaning and other processes, that is, semiconductor substrate material;

3) In the epitaxial wafer link, chemical vapor deposition (CVD) is usually used to deposit a layer of single crystal on the wafer to form an epitaxial wafer;

4) Wafer processing, silicon carbide wafers formed by front-end processes such as photolithography, deposition, ion implantation, and metal passivation can be made into silicon carbide chips through post-process processes;

5) Device manufacturing and packaging testing, the manufactured electronic power devices and modules can be verified and entered into the application link.

The whole process from production to application of silicon carbide products takes a long time. Taking silicon carbide power devices as an example, it takes 1 month from single crystal growth to substrate formation, and 6-12 months from epitaxial growth to wafer front and rear processing, from device manufacturing to on-board verification. It will take 1-2 years more. For silicon carbide power device IDM manufacturers, the period from industrial design, application, etc. to revenue growth is very long, and the automotive industry generally takes 4-5 years.

|Substrate: The value accounts for 46%, which is the core link

The substrate is finally formed from the SiC powder through the processes of crystal growth, processing, cutting, grinding, polishing and cleaning. Among them, the growth of SiC crystal is the core process, and the core difficulty is to improve the yield. Types can be divided into conductive, and semi-insulating substrates, which are used in the fields of power and radio frequency devices, respectively.

As far as the technical route is concerned, the production methods of single crystal of silicon carbide mainly include physical vapor transport (PVT), high temperature vapor chemical deposition (HT-CVD), liquid phase method (LPE) and other methods. The mainstream method is the relatively mature PVT method.

PVT: The stability of the growth system is not good, the crystal growth efficiency is low, it is easy to produce serious quality problems such as disorder of the standard crystal form and various crystal defects, so the cost is high.

HT-CVD: It started late and can prepare high-purity, high-quality semi-insulating silicon carbide crystals, but the equipment is expensive and the high-purity gas is expensive.

LPE: not yet mature, it can greatly reduce the production temperature and increase the production speed, and the melt itself is easier to expand under this method, and the crystal quality is also greatly improved, so it is considered to be a better path for silicon carbide materials to move towards low cost. Positive development space.

|Substrate: The general trend of large size is the core of SiC industrialization and cost reduction

At present, the price of a 6-inch silicon carbide substrate is about US$1,000/piece, which is several times that of traditional silicon-based semiconductors. Production efficiency (more mature crystal growth process).

Growth end: SiC contains more than 200 crystal forms of isomeric structure, but only a few such as 4H type (4H-SiC) are the desired crystal forms. However, the entire reaction of PVT crystal growth is in a high temperature of 2300°C, in a completely closed chamber (similar to a black box), and the transformation of different crystal forms is easy to occur. Any fluctuation of growth conditions will affect the crystal growth. Difficult to find the best growing conditions. At present, the mainstream yield rate in the industry is around 50-60% (the traditional silicon base is above 90%), and there is a large room for improvement.

Machining end: The hardness of silicon carbide is close to that of diamond (Mohs hardness is 9.5), cutting, grinding and polishing techniques are difficult, and the improvement of the technological level requires long-term R&D accumulation. At present, the mainstream yield rate in the industry is around 70-80%, and there is still room for improvement.

Improve production efficiency (more mature crystal growth process) : The speed of SiC crystal growth is extremely slow, and the industry average can only grow 0.2-0.3mm per hour, which is nearly a hundred times slower than the growth rate of traditional crystalline silicon. In the future, further maturity of PVT process or extension to other advanced processes (such as liquid phase method) is required.

|SiC substrate equipment: the difference from traditional crystalline silicon is small, and process tuning is the core barrier

SiC substrate equipment mainly includes: crystal growth furnace, slicer, grinder, polishing machine, cleaning equipment, etc. It is compatible with traditional traditional crystalline silicon equipment, but the process is more difficult, and the cooperative research and development of equipment + process is the key.

|Epitaxy equipment and epitaxial wafers: value accounted for 23%

The essence is to cover a layer of thin film on the substrate to meet the conditions of device production. Specifically, it is divided into: conductive SiC substrates are used for SiC epitaxy, and then power devices are produced for electric vehicles and new energy fields. Semi-insulating SiC substrates are used for GaN epitaxy, which in turn produces RF devices for 5G communications and other fields.

The global SiC epitaxy equipment is monopolized by the four leading companies in the industry, Axitron, LPE, TEL and Nuflare, and each has its own advantages.

|Power devices: the value accounts for about 20% (including design + manufacturing + packaging)

The production of SiC power devices is divided into chip design, manufacturing and packaging and testing. The products include SiC diodes, SiCMOSFETs, full SiC modules (composed of SiC diodes and SiCMOSFETs), and SiC hybrid modules (composed of SiC diodes and SiCIGBTs) . At present, the manufacturers of silicon carbide in China are mainly IDMs, and a small number are pure design enterprises.