Published online 25 August 2004 | Nature | doi:10.1038/news040823-9

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Computer chips get tough

Near-flawless silicon carbide crystals bring extreme electronics a step closer.

Electronic devices using silicon carbide could be much more efficient than exisiting silicon chips.Electronic devices using silicon carbide could be much more efficient than exisiting silicon chips.© PhotoDisc

A method to make virtually perfect crystals of silicon carbide could revolutionize the electronics industry. The technique may pave the way for tougher and more efficient circuits.

Silicon carbide (SiC) is much better than silicon at carrying current in an electronic circuit, so it could potentially reduce the amount of energy wasted in every electronic device in the home or office. It can also operate at much higher temperatures, meaning that silicon carbide-based sensors could even monitor jet engines from the inside.

Scientists have long recognized the potential of silicon carbide to replace silicon chips, but until now it has proved tricky to make sufficiently large crystals without introducing defects that interfere with reliability. These defects are tiny tunnels that run through the centimetre-sized crystals, effectively short-circuiting them and rendering them useless for electronics applications.

The solution to this problem is revealed in this week's edition of Nature1 by Kazumasa Takatori of the Toyota Central Research and Development Laboratories in Nagakute, Japan, and his colleagues.

“This will have major implication for society.”

Nick Wright
University of Newcastle upon Tyne, UK.

Takatori grows the silicon carbide crystals in several different stages. At each stage, further growth is only allowed on the cleanest face of the crystal. Hot silicon carbide vapour condenses on the crystal's flat face and defects are gradually eliminated as the crystals grow up to seven centimetres across. Takatori's crystals contain less than 1% of the number of defects found in a crystal produced by conventional methods.

"This has been an immense challenge for many years, and it will have major implication for society," predicts Nick Wright, an electronics expert at the University of Newcastle upon Tyne, UK.

Domestic impact

More efficient electronics could make quite an impact on a domestic electricity bill, Wright explains. For example, your washing machine's motor is controlled by a silicon chip, which varies the speed of the drum by pulsing electricity to the motor.

When silicon electronics are used to control motors about half of the electrical energy that flows through the circuit is wasted. In contrast, silicon carbide circuits would be up to 70% efficient, Wright says. This is because silicon can only handle low-frequency pulses, whereas silicon carbide can carry electricity at a much higher frequency, incurring far less energy loss.

Hot stuff

Not only is it efficient, silicon carbide can also withstand much higher voltages than silicon. "We believe silicon carbide is one of the most excellent materials for high-power electronic devices," says Takatori. He adds that silicon carbide could even be used in radiation-proof devices, which might find a home in sensors on the outsides of spacecraft or deep inside nuclear reactors.

And the material can cope with much higher temperatures than silicon, which usually requires heat shielding when used in circuits close to hot motors. Such shielding is often more expensive that the devices themselves.

Wright suggests that silicon carbide could stand the heat inside a jet engine, so it could be used in devices that would precisely control the supply of fuel. This could make significant fuel savings and even reduce aircraft engine emissions, he says.

Many of these devices have already been developed, says Wright, but they have always been plagued by flawed crystals. At least 50% of silicon carbide crystals grown using conventional methods have too many defects, which has always made the material too expensive for the semiconductor industry to adopt.

Takatori and his colleagues are now developing their method to make it more cost-effective, and anticipate that it will soon be used to make commercial silicon carbide devices. 

University of Newcastle upon Tyne, UK.

  • References

    1. Makamura D., et al. Nature, 430 1009 - 1012 (2004). doi:10.1038/nature02810 | Article |