This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the grant agreement No 953549.
Why is Silicon Carbide important?
Silicon Carbide (SiC) is a surging semiconductor. Among different semiconductors, the most commonly used today are industrially grown Silicon (Si) and Gallium Arsenide (GaAs). However, recently there has been a shift in the market—silicon carbide is attracting more and more investment due to its superior properties. Compared to conventional silicon-based devices, SiC offers almost 10X the breakdown field strength (2.8MV/cm vs 0.3MV/cm) and 3X the thermal conductivity, making it ideal for high-voltage applications: electric cars, power supplies, solar inverters, trains and wind turbines. Its superior conductive properties are increasingly necessary for automotive and power generation devices operating at higher voltages, higher temperatures, and higher frequencies than ever before.
Another benefit is that a SiC epitaxial layer deposited on a substrate could be much thinner, down to one-tenth of a traditional Si epitaxial layer. For example, the SiC epitaxy on SiC substrates provides a range of available layer thicknesses from sub-micron to more than 200µm. In comparison, this is is about one-tenth of that of Si epitaxial layers.
Additionally, SiC devices reduce the amount of energy lost in a system, improve performance, reliability, and cut operating costs. For instance, in hybrid and electric vehicles SiC power solutions contribute to increased fuel economy and a larger cabin area, while in solar power generation applications they improve power loss by approximately 50%, contributing to reduced global warming.
Due to these advantages, SiC is expected to become the standard material used for power electronics applications over the next few years.
Crystal growth and defectiveness
SiC boules are typically crystallised by one of the two processes:
1. Sublimation method (often called “Rayleigh’s method”) that sublimates SiC powder, transports sublimated gas to the surface of the seed crystal by a heat gradient, and recrystallises it under cold temperatures. Compared with conventional Si ingots which are crystallised in the liquid phase from Si melt, the growth rate using the sublimation method is slow, making crystal defects likely to occur, and therefore requires advanced technology for crystal control.
2. High-Temperature Chemical Vapour Deposition (HTCVD). The method feeds precursor gases upwards through heating zone in vertical graphite crucible to the seed crystal placed at the top. The precursor gases are SiH4 and a hydrocarbon. The growth temperature is ~2100–2300°C, the growth rate is 0.1-1mm/h.
Crystal growth is the most difficult step in the material value chain.The growth is a completely blind process – there is no way to see or directly measure what is growing. As a result, compared with Silicon, SiC is a highly defective material. Typical defects are micropipes and dislocations within the atomic lattice. Each defect degrades the manufacturing yield and reliability for SiC power devices. The micropipes reduce blocking voltage and gate oxide reliability. The dislocations do the same, and also reduce local carrier lifetime.
Scientific Visual is working to create such an early-stage inspection system to visualise defects in raw SiC crystals. We will publish project news on this page. Our expert staff is happy to test your samples and to apply early-stage inspection technology to your production. Please contact us at your earliest convenience at email@example.com.
Silicon Carbide vs Gallium Nitride
|Band Gap (eV)||3.2||3.4|
|Critical Field 10e6 V/cm||3||3.5|
|Electron Mobility (cm2/V-sec)||900||2000|
|Electron Saturation mobility (106 cm/sec)||22||25|
|Thermal Conductivity (Watts/cm2 K)||5||1.3|
Silicon Carbide market
- Dhanaraj G, Raghothamachar B, Dudley M, editors. Handbook of crystal growth-Chap 23- and Characterization of Silicon Carbide Crystals. In: Handbook of crystal growth- Heidelberg ; New York: Springer; 2010.
- Wellmann PJ. Review of SiC crystal growth technology. Semiconductor Science and Technology. 2018 Oct 1;33(10):103001.
- Kimoto T, Cooper JA. Fundamentals of silicon carbide technology: growth, characterization, devices and applications. Singapore: John Wiley & Sons Singapore Pte. Ltd; 2014. 538 p.
- Lapedus M. SiC Demand Growing Faster Than Supply. 2019 May 23 ; Available from: https://semiengineering.com/sic-demand-growing-faster-than-supply/