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Use of `hot wafers' are one step closer to becoming reality

One of the last frontiers of semiconductor technology -- environments where electronic devices have to run at high power, in fierce heat or at lethal doses of radiation -- may be about to fall.

If an engineering breakthrough can be carried forward into the commercial domain, a new generation of silicon carbide (SiC) semiconductors could help make jets and cars cleaner and more powerful, provide clear radio and telephone communications and send spacecraft on missions previously deemed suicidal.

That is the dream of a team of Japanese scientists, who believe their new way of making SiC crystals could make larger and more reliable wafers of this material, rendering them cheaper and more useful than ever before.

Conventional computer chips comprise a thin slice of silicon, which is made by cooling pure, molten silicon in such a way that, as the fiery drop solidifies, a crystal "grows" in a certain direction.

Ground into a wafer and then cunningly doped with chemicals to tease out conductive circuitry, the silicon can then etched to house millions of electronic components.

The problem, though, is that silicon devices are very sensitive to heat.

They can malfunction in high temperatures -- even from heat generated by their own circuitry, a factor that requires fans or other gadgets to cool them down and limits their future miniaturization.

But: SiC crystals have been hard to manufacture in large crystals that are of high quality. They are prone to a flaw called micropipes -- microscopic tubes that damage or weaken the circuitry and make the chip vulnerable to failure.

That hitch has now been overcome thanks to a new way of growing SiC crystals, according to research published on Thursday in the British weekly scientific journal Nature.

A team led by Kazumasa Takatori of Toyota Central R&D Labs Inc of Japan found a solution by growing the crystals in several different stages. At each stage, the crystal is carefully rotated so that the solidifying compound crystallizes on the best, least-blemished face. By patiently building up the crystal layer by layer, ingots of SiC -- the little bricks from which wafers are sliced -- are "virtually dislocation-free," they say.
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