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Pratap Ravindran

With breakthroughs in the process of chemical vapour deposition (CVD), the semiconductor industry is poised to enter a new phase in which the hardest substance known to man will replace silicon.

WITH the mass manufacture of gem quality diamonds through improved chemical vapour deposition now becoming viable, the semiconductors industry is poised to enter a new phase in which the hardest substance known to man will replace silicon.

Chipmakers have been uncomfortably aware for quite some time now that microprocessors are running hotter — 200 degrees Fahrenheit and above — with the steady increase in their speed and that, soon, they'll be hitting temperatures which will turn silicon into a puddle. They have also been aware that diamond has many properties that make it superior to silicon: Diamond has a higher band-gap than silicon, can tolerate higher temperatures, and has the potential to form transistors that switch faster than silicon.

However, they haven't been able to switch because, till recently, diamond fabrication technologies were not economical enough to be incorporated in mass semiconductor fabrication. Inevitably, a lot of researchers were working on finding ways to mass-produce diamond wafers inexpensively and to discover a means of effectively doping diamond substrates.

The breakthrough that they've been waiting for has come with the development of a process called chemical vapour deposition(CVD).

CVD has been in use for over a decade now to coat relatively large surfaces with microscopic diamond crystals. The process basically transforms carbon into plasma that precipitates on to a substrate as diamond. The technology was just fine — except for the fact that nobody could figure out how to grow a single crystal.

That has changed with two start-ups — the Florida-based Gemesis and Apollo Diamond in Boston — making it known that they were able to produce large diamond wafers at a low cost and that they were planning to use the money they would make in the diamond jewellery business to fund their move into supplying the semiconductors industry with an affordable substitute for silicon.

The industry is in seventh heaven: These start-ups are talking about producing inch square wafers in a year and four inches in five years — at five dollars a carat!

The funny thing here is that the media, ever blind to the big picture, is reporting the breakthrough in the mass manufacture of gem quality diamonds with the jewellery trade as the focus and without paying much attention to the implications with regard to the semiconductors industry.

Further, most of the hype is around what the start-ups are doing.

Actually, the US military has been trying to come up with a semiconductor diamond substrate for years.

The US Navy's diamond research project — Code 6174 — is a case in point. The project been researching CVD diamonds and semiconducting for the military for 16 years and, till recently, was stuck at three points — the high cost of natural diamonds the supply of which is kept low by De Beers, the inadequate availability of pure diamonds of the required size and the variability in the electrical properties of mined diamonds.

With CVD technology, all these problems have been blown away.

Further, the technology has taken care of another problem which has been bugging material scientists all along. Positive and negative conductors are required for the formation of microchip circuits. But natural diamond doesn't conduct electricity — it's an insulator. CVD diamonds, on the other hand, have boron injected into their lattices and can carry a positive charge. That fixed a part of the problem — but nobody could figure out how to make a negatively charged (n-type) diamond with the necessary conductivity. However, the word is that scientists in Israel and France have very recently claimed success in inverting boron's natural conductivity to form a boron-doped n-type diamond. So now they have a p-n junction, which means that a diamond semiconductor is very much a real option.

With the availability of inexpensive, mass manufactured diamonds, the Defense Advanced Research Projects Agency (DARPA) too has been seeking proposals for defence applications.

The question now is whether the US computer industry will be able to run with the ball. As of now, it looks as if it won't because Europe and Japan are reported to be far ahead in building a first-generation diamond-chip. As for India, we should start thinking about projecting Surat as the global centre of next generation hardware.

eworld@thehindu.co.in

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