Last Login: 01-19-22
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 to Create Silicon Carbide
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 product 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.
How is Silicon Carbide Useful?
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.
In recent years, SiC has become a key player in the semiconductor industry, powering MOSFETs, Schottky diodes, and power modules for use in high-power, high-efficiency applications. While more expensive than silicon MOSFETs, which are typically limited to breakdown voltages at 900V, SiC allows for voltage thresholds at nearly 10kV.
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.
In the solar industry, SiC-enabled inverter optimization also plays a large role in efficiency and cost savings. Utilizing silicon carbide in solar inverters increases the system's switching frequency by two to three times that of standard silicon. This switching frequency increase allows for a reduction in the circuit's magnetics, resulting in considerable space and cost savings. As a result, silicon carbide-based inverter designs can be nearly half the size and weight than that of a silicon-based inverter. Another factor that encourages solar manufacturers and engineers to use SiC over other materials, such as gallium nitride, is its robust durability and reliability. Silicon carbide's reliability enables solar systems to achieve the stable longevity they need to operate continuously for over a decade.
Saving the World with Silicon Carbide
Several key leaders in the silicon carbide space are providing bountiful resources and products centered around SiC. Cree Wolfspeed offers a variety of silicon carbide products, such as:
- AEC-Q101 (automotive) rated MOSFETs
-Bare die solutions
Cree Wolfspeed is also the largest manufacturer of base SiC wafers, making them an expert in all things SiC. Cree is dedicated to expanding silicon carbide's feasibility and adoption by 2024. To learn more, check out their full offering of silicon carbide solutions.
Silicon Labs offers excellent isolation solutions specifically aimed at supporting silicon carbide-based designs in the electronic vehicle market. Their target solutions range from battery management systems to traction control inverters that rely on high-frequency power distribution. For more information on Silicon Labs solutions, you may want to learn about how they are revolutionizing EV power. Other semiconductor companies, such as Rohm Semiconductor, boast large portfolios of silicon carbide products as well, including power MOSFETs and power modules.