Why Demand for SiC Wafers is Hot and Durable
Pardon the pun, but SiC wafers are a hot item for high-temperature applications. Silicone carbide (SiC), a semiconductor containing both silicon and carbide, withstands temperatures up to 2700°C. Carborundum, as this durable ceramic is also known, finds additional applications in bulletproof vests, extrusion dies, sandpaper, and high-performance disc brakes. In electronics, SiC materials are used with light-emitting diodes (LEDs) and detectors. In the semiconductor industry, a market where interest is red-hot, SiC wafers are used in electronic devices that operate at high temperatures, high voltages, or both. Examples include electric vehicle (EV) power electronics and 5G communication systems.
Bandgap and Thermal Conductivity
With its wide bandgap, silicon carbide wafers can withstand voltages that are up to ten times higher than silicon, which has a breakdown voltage of around 600V. Silicon (Si), a semiconductor that’s long been the material of choice for the wafers used in integrated circuits (ICs) and photovoltaics, has a bandgap of 1.12 eV. Gallium arsenide (GaAs), a semiconductor used in solar cells, has a bandgap of 1.42 eV. By contrast, silicon carbide has a bandgap of 3.26 eV. SiC’s wider bandgap also support faster, more efficient switching and smaller, thinner devices. In addition, silicon carbide’s higher thermal conductivity allows for the more efficient transportation of heat and can reduce or eliminate the need for heat sinks in electronic designs.
Thermal Shock Resistance
With its high thermal conductivity and low thermal expansion, silicone carbide also provides superior resistance to thermal shock, a transient mechanical load caused by a rapid change of temperature. Often, thermal shock occurs when an extreme temperature gradient reaches some but not all of an object. Because of this difference in temperature, parts of the object expand and contract at different rates, which can lead to fracture. Compared to most semiconductor materials, SiC has a low thermal conductivity (3.8 W/m.K minimum) and a high thermal expansion (7.9 to 11 10-6/K).
Physical, Chemical and Electrical Durability
Silicon carbide’s physical durability is demonstrated by its use in non-electronic applications such as the plates in bulletproof vests. With regard to temperature durability, SiC will not sublimate into a vapor phase until around 2700°C, which is significantly higher than the melting point of iron (around 1500°C). SiC is also chemically inert and can resist very aggressive chemicals such as alkalis and molten salts, even at high temperatures up to 800°C. With its high energy bandgap, SiC is extremely resistant to high levels of electromagnetic disturbances and the damaging effects of radiation.
Applications for SiC Wafers
Silicone carbide’s superior properties makes it good choice for EV power electronics. Applications include on-board DC/DC converters, off-board DC fast chargers, on-board battery chargers, EV powertrains, and automotive lighting for LEDs. In addition to high-temperature resistance, silicon carbide provides the low power consumption, rigidity, and support for smaller, thinner designs that EV power electronics need. With their greater power densities and higher amounts of heat, 5G electronics are also using SiC wafers. According to Cree Wolfspeed, gallium nitride (GaN) on SiC is “the optical solution for 5G”.
SiC Wafer Measurement and Inspection
Silicon carbide’s prospects remain hot and durable, but increased demand could result in component defects unless manufacturers install proper inspection equipment. This is especially important during research and development (R&D), where poor verification of process tools can dramatically reduce yield. MTI Instruments’ Proforma 300iSA system performs wafer inspection at-scale (up to 20 wafers fer hour) for increased throughout of SiC materials. This semi-automated measurement system delivers full water surface scanning for thickness, total thickness variation (TTV), bow, site, global flatness and more. For
To learn more about MTI’s measurement solutions for SiC wafers, or to download a sample wafer inspection report please contact MTI Instruments.
