Silicon Carbide

Silicon carbide, also known as SiC, is a semiconductor base material that consists of pure silicon and pure carbon. You can dope SiC with nitrogen or phosphorus to form an n-type semiconductor or dope it with beryllium, boron, aluminum, or gallium to form a p-type semiconductor. While many varieties and purities of silicon carbide exist, semiconductor-grade quality silicon carbide has only surfaced for utilization in the last few decades.

How is silicon carbide made?
The simplest silicon carbide manufacturing method involves melting silica sand and carbon, such as coal, at high temperatures―up to 2500 degrees Celsius. Darker, more common versions of silicon carbide often include iron and carbon impurities, but pure SiC crystals are colorless and form when silicon carbide sublimes at 2700 degrees Celsius. Once heated, these crystals deposit onto graphite at a cooler temperature in a process known as the Lely method.

Lely method: During this process, a granite crucible heats to a very high temperature, usually by way of induction, to sublimate silicon carbide powder. A graphite rod with lower temperature suspends in the gaseous mixture, which inherently allows the pure silicon carbide to deposit and form crystals.

Chemical vapor deposition: Alternatively, manufacturers grow cubic SiC using chemical vapor deposition, which is commonly used in carbon-based synthesis processes and used in the semiconductor industry. In this method, a specialized chemical blend of gases enters a vacuum environment and combines before depositing onto a substrate.
Both methods of silicon carbide wafer production require vast amounts of energy, equipment, and knowledge to be successful.

What is silicon carbide used for? Advantages of SiC
Historically, manufacturers use silicon carbide in high-temperature settings for devices such as bearings, heating machinery components, car brakes, and even knife sharpening tools. In electronics and semiconductor applications, SiC's advantage main advantages are:

• High thermal conductivity of 120-270 W/mK
• Low coefficient of thermal expansion of 4.0x10^-6/°C
• High maximum current density

These three characteristics combined give SiC excellent electrical conductivity, especially when compared to silicon, SiC's more popular cousin. SiC's material characteristics make it highly advantageous for high power applications where high current, high temperatures, and high thermal conductivity are required.
SiC also has very low switching losses and can support high operating frequencies, which allows it to achieve currently unbeatable efficiencies, especially in applications that operate at over 600 volts. With proper implementation, SiC devices can reduce converter and inverter system losses by nearly 50%, size by 300%, and overall system cost by 20%. This reduction in overall system size lends SiC the ability to be extremely useful in weight and space-sensitive applications.

Silicon carbide applications
Many manufacturers are charging forward in using SiC in applications such as electric vehicles, solar energy systems, and data centers. These efficiency-oriented systems all result in high voltages and high temperatures. We're seeing a significant global push to implement SiC over other materials in an effort to reduce carbon emissions caused by power inefficiencies at higher voltages. Although cutting-edge technologies such as electric vehicles and solar energy are pioneering the utilization of SiC, we expect to see more legacy industries follow suit soon.

SiC has become popular in the automotive sector as a result of the industry's demand for high quality, reliability, and efficiency. SiC can answer high voltage demands with prowess. Silicon carbide has the potential to increase electric vehicle driving distances by increasing the overall system efficiency, especially within the inverter system, which increases the vehicle's overall energy conservation while reducing the size and resultant weight of battery management systems.

Goldman Sachs even predicts that utilizing silicon carbide in electric vehicles can reduce EV manufacturing cost and cost of ownership by nearly $2,000 per vehicle. SiC also optimizes EV fast-charging processes, which typically operate in the kV range, where it can reduce overall system loss by almost 30%, increase power density by 30%, and reduce the component count by 30%. This efficiency will allow fast charging stations to be smaller, faster, and more cost effective.

With the continuous development of electric vehicles, smart grids, nuclear power and solar energy, as well as energy fields such as navigation, aviation, aerospace, and high-speed rail transportation, we have put forward higher requirements for the performance of power equipment. However, at present, the first generation of semiconductor materials based on silicon materials is approaching the theoretical limit determined by its properties. The third-generation semiconductor materials have wider bandwidth, higher breakdown electric field, thermal conductivity, electron saturation and higher radiation resistance, making them suitable for manufacturing high temperature, high frequency, radiation resistant and high power devices. They are promising to replace the first generation of semiconductor material silicon to meet the higher requirements of the future, and will be more widely used in the industry. Silicon carbide ceramic materials are the most mature third-generation semiconductor materials and one of the most potential applications. Its various indicators are superior to silicon, and its bandwidth is almost three times that of silicon. In addition, the theoretical operating temperature of silicon carbide devices is 600 ° C, much higher than silicon devices. The following are the applications of silicon carbide in various fields:

Electric Vehicles
As the core advanced electronic material for electric vehicle charging modules and electrical modules, silicon carbide can achieve green, low carbon, intelligent and sustainable development. The advantages of using silicon carbide as an energy supply are mainly reflected in three aspects:

• Increasing the frequency and simplifying the power supply network;
• Reducing losses and temperature rise; and (3) reducing volume and improving efficiency.

Silicon carbide components can improve the power conversion performance of pure electric vehicles or hybrid vehicles. In the electric module of an electric vehicle, the electric motor is an active load, and its rotational speed range is wide, and frequent acceleration and deceleration are required in the driving process, so the working condition is more complicated than the general speed regulating system.

New Transmission System
The silicon carbide power switch is an ideal replacement for silicon-based devices because of its extremely low open circuit resistance for high voltage, high temperature and high frequency applications. The use of silicon carbide components can reduce power losses by more than five times while reducing size and weight by more than 40%, which will have a major impact on future grid configuration and energy strategy adjustments.

Solar Energy field
Silicon carbide power devices are suitable for some high power module applications such as solar inverters. It enables smaller sizes, lower material costs and higher efficiency. The typical conversion efficiency of the new standard solar silicon-based inverter is close to 96%, while the average efficiency of the silicon carbide-based inverter can be increased to 97.5%, which is equivalent to a 25% reduction in inverter losses. In addition, silicon carbide based inverters can increase conversion efficiency by 20% in wind farms.

LED Lighting
At present, the third-generation semiconductor material technology and application of LED optoelectronic devices made of silicon carbide as the core material is becoming a new strategic high ground for the global semiconductor industry. Silicon carbide LED lighting equipment can reduce the number of original LED lights by 1/3, reduce the cost by 40-50%, and increase the brightness by two times, and increase the thermal conductivity by more than 10 times. In daily life, silicon carbide LED semiconductor lighting can also be applied to various signal lights, indoor lighting, information screens, color display devices, etc., which can achieve higher electro-optical conversion efficiency, and achieve significant purposes to reduce cost and pollution.

• Their colors are different, black silicon carbide ( short for C) is black, green silicon carbide (short for GC) is green.
• Black SiC is quartz sand, petroleum coke in primary raw materials, smelting in high temperature electric resistance arc furnace. Green SiC is made from quartz sand and petroleum coke, appended with salt, then smelted in high temperature electric resistance arc furnace.
• Black silicon carbide has SiC content about 98% min., while green silicon carbide has SiC content about 99% min.
• Green SiC is harder than black SiC although they are both Mohs hardness is 9.2.

Similarities are as follows:

• Both are man-made materials, not belong to natural mineral materials.
• They are both used in abrasives products( blasting media, polishing media,grinding wheels, cutting wheels,flapping discs etc.) or high advanced refractory materials, used as semi conductor material and metallurgical deoxidizer.
• Both main material content of finished product is silicon carbide (SiC).
• Both max.usable temperature in air is 1900 Celsius degree, decomposition point is 2600 Celsius degree.
• They have similar bulk density (1.2~1.6g/cm3) and true density (3.20~3.25g/cm3).