PORTLAND, Ore. The National Aeronautics and Space Administration thinks silicon carbide is ready to replace silicon in circuitry that must withstand ultrahot temperatures--as high as 1,000 degrees F--or deliver ultrahigh power. Prototypes of the world's first commercial SiC integrated circuit, which NASA has contracted with Inprox Technology Corp. (Boston) to jointly design and fabricate, are due out by the end of 2008.
The position sensor is being designed to measure linear motion inside NASA's turbine propulsion engines, but Inprox also plans to repurpose it for automotive engine control as well as for high-power, high-temperature industrial applications.
"For NASA, the major advantage of silicon carbide circuitry is its ability to handle the high temperatures in our advanced electronic sensing and control systems, slated for the hot sections of jet engines," said NASA electrical engineer Phil Neudeck, the team leader. The silicon carbide group has been tasked to help sense the harsh environment inside aircraft engines at NASA's Glenn Research Center in Cleveland. "We need these sensors to improve the safety and fuel efficiency of jet aircraft engines, while reducing weight and pollution."
Traditional electronics must either be remotely located or liquid-cooled, Neudeck said, "which seriously hampers their ability to achieve desired safety and performance specifications." But SiC can function in an engine environment at 500 degrees C (932 degrees F) without cooling, he said. The work is funded under NASA's Aviation Safety and Fundamental Aeronautics Programs.
Silicon carbide is a rare natural material called moissanite. Its synthesized form, carborundum, is widely used in industry as an abrasive. At the leading edge of the electronics industry, highly purified SiC wafers are being used to fabricate semiconductor devices that have the potential to transform the market for ruggedized electronics by enabling ultrahigh-power, ultrahigh-temperature components.
A wide-bandgap material, silicon carbide's electron mobility is not quite as high as silicon's (900 cm2/V-s compared with 1,500 cm2/V-s). But almost all of its high-temperature and high-power electronic properties are superior to those of silicon.
SiC's advantages have been well known for more than a decade, but building integrated circuitry for durable operation at extreme temperatures well beyond limits of silicon has been a challenge. Pioneering fabricators were plagued with defects and high costs. Slowly but surely, however, over the last 10 years, many of the major engineering hurdles have been cleared.
Now, discrete devices for nonextreme environments are being fabricated by vendors like Cree Inc. (Durham, N.C.), which offers high-power silicon carbide discrete transistors and rectifiers. However, Inprox's higher-temperature design, which will be fabricated using the NASA-developed chip technology, could prove to be the first commercial IC to take advantage of SiC's extreme-temperature attributes.