Silicon Carbide (SiC)

• Silicon carbide material manufacturing process

1. Raw material preparation

High purity silicon (SI) and carbon (C) are the main raw materials, and the purity is usually required to be greater than or equal to 99.9999% (6N grade).

2. Backing processing technology

Cutting and grinding: Use diamond wire or laser cutting, combined with grinding process to control the thickness (usually 300-600 ΜM).

Chemical mechanical polishing (CMP): reduce the surface roughness to the nanometer level to meet the requirements of epitaxial layer growth.

Defect detection: Defects such as dislocations and microtubes are screened by X-ray diffraction (XRD) and infrared imaging (IR).

3. Crystal growth

Physical vapor transport (PVT):

In high temperature (2300-2500℃) and low pressure (10-100 MBAR) environment, the current mainstream method is to sublimate SIC powder and crystallize on the seed crystal.

Advantages: mature process, suitable for 4-8 inch substrate production.

Challenge: slow growth rate (about 0.1-1 MM/H) and strict control of temperature gradient and gas flow.

Liquid phase method (LPE):

Carbon and silicon are dissolved by metal solvents (such as aluminum and tantalum), and SIC crystals are precipitated on the seed crystal.

Advantages: fast growth rate (up to 10 MM/H) and low defect density.

Challenge: high temperature and high pressure conditions are harsh, solvent pollution risk is high.

Chemical vapor deposition (CVD):

The epitaxial growth of methane (CH₄) and silane (SIH₄) on the substrate surface at high temperature is suitable for thin film preparation (epitaxial sheet).

4 Material purity and crystal type control

High purity requirements: the purity of raw materials should reach 6N (99.9999%), and impurities (such as boron, aluminum) affect the type of conduction.

Crystal type selection: common 4H-SIC and 6H-SIC, 4H-SIC is the mainstream of power devices due to higher electron mobility.

5. Wafer processing

Silicon carbide crystals are cut into wafers (typically 150-300 ΜM thick) and then polished, cleaned, and surface treated. Diamond wire sawing is commonly used for slicing, but the high hardness of silicon carbide results in significant cutting loss (40% of ingots become scrap). Subsequently, the wafers need to be ground and polished to achieve a surface roughness of <0.2 NM, and chemical mechanical polishing (CMP) is employed to optimize surface quality

6. Doping and device manufacturing

The electrical properties of silicon carbide can be adjusted by ion implantation or diffusion techniques to incorporate elements such as nitrogen (N) and aluminum (AL).

Shottky diodes (SBD), field-effect transistors (FET) and other devices are manufactured by lithography, etching, deposition and other processes.

7. Packaging and testing

The device is packaged into a chip module and the electrical performance test and reliability verification are carried out.

• Advantages of technical indicators of materials

1. Electrical properties

Wide band gap (3.3 EV): The breakdown electric field strength is 2.8 x 10⁶V/CM, much higher than silicon’s 3 x 10⁵V/CM. It is suitable for high power RF devices and high voltage (above 1200V) devices, supports higher voltage devices, and is suitable for electric vehicle inverters and high voltage power grids

High thermal conductivity (490 W/ (M K)): 3 times that of silicon, strong heat dissipation ability, improve the power density of devices, suitable for aerospace and industrial high temperature environment.

High electron saturation drift speed (2.2 x 10⁷ CM/S): supports high frequency (100 KHZ-1 MHZ) switching, reducing loss.

2.environmental suitability

High temperature resistance: it can work stably above 600℃, far exceeding silicon (150℃) and gallium nitride (300℃).

Radiation resistance: stable performance in high radiation environment such as nuclear reactor and space.

Chemical stability and high hardness and wear resistance: Mohs hardness 9.5, used for mechanical seals; resistant to strong acids and alkalis, suitable for sensor applications in harsh environments.

3. High frequency and low loss

High frequency devices: The electron mobility is up to 900CM²/V S, supporting high frequency signal transmission. In 5G base stations, the output power density of SIC base RF device (MESFET) is 10 times that of GAAS.

Power devices: The switching loss of SIC MOSFET is 80% lower than that of silicon IGBT, and the on-state resistance (RDS(ON)) is reduced by 90%, which significantly improves energy conversion efficiency.

4. Photoelectric properties

Blue light/ultraviolet emission: band gap width covers blue light (460 NM) to ultraviolet (370 NM) for LED and detector.

Solar cells: multi-junction laminated cells with efficiency of more than 30% are suitable for spacecraft and desert photovoltaic power stations.

Direct band gap material (band gap width 3.2EV), suitable for ultraviolet light devices

• Competitive advantages of silicon carbide materials

1. Power electronics

The power density of silicon carbide devices is 10 times higher than that of silicon based devices, suitable for miniaturized and efficient power supply design.

2. Radio frequency communication field

The efficiency of silicon carbide based HEMT is increased by 20% and power consumption is reduced by 30% in 5G base stations.

3. High temperature devices

Silicon carbide sensors can operate at temperatures up to 600℃, much higher than silicon-based sensors.

• Core application areas

1. Power electronics and new energy

Electric vehicles: Silicon carbide MOSFET is used in inverters to improve the range by 10%~15%. Tesla, BYD and other car companies have adopted it on a large scale.

Photovoltaic and energy storage: The efficiency of photovoltaic inverters is increased to more than 98%, reducing energy conversion loss.

2. Communications and data centers

5G base station and RF devices: Semi-insulating silicon carbide substrate for gallium nitride (GAN) HEMT devices, supporting millimeter wave communications.

AI data center power supply: silicon MOSFET replaces silicon devices, improves power factor correction (PFC) efficiency, and reduces energy consumption by 12%~15%.

3. High temperature and extreme environment

Aerospace: radar, satellite power, nuclear reactor monitoring sensors, high temperature resistant components (rocket nozzles) and radiation resistant electronics.

Industrial manufacturing: hot pressed silicon carbide ceramics are used in wear-resistant bearings, welding machines, frequency converters, high temperature kilns (volume reduced by 50%), life increased by 5 to 20 times.

4. Emerging areas

AR/VR optical waveguide: High refractive index silicon carbide lens replaces glass to solve the problems of small field of view and heavy lens, and promote the development of lightweight AR equipment.

Quantum technology: as a single photon source material, it supports quantum communication and computing.

• Future development trends

1. Process optimization

Breakthrough in 8-inch wafer mass production technology and reduce substrate cost (current 6-inch yield target>80%)

2. Development of new devices

Heterogeneous integration: Develop GAN-ON-SIC and SIC-ON-SI technologies to balance performance and cost.

3. Application extension

Promote silicon carbide devices in 6G communications, autonomous driving and the Internet of Things (IOT).

The global SIC power semiconductor market is expected to reach $15 billion by 2028, with a compound annual growth rate of 46%, from approximately $2 billion in 2024. Silicon carbide, through single-crystal growth technology combined with precision substrate processing, has developed unique advantages in high power, high-temperature resistance, and radiation tolerance. Despite the complexity of manufacturing processes, its performance benefits are being rapidly accelerated by the surge in demand from electric vehicles and the energy internet, driving technological iteration and large-scale application, making it a key material for achieving the “carbon neutrality” goal.