Diamond chips oust saphhire for semicon ICs

The semiconductor industry may soon be rolling out the red carpet for diamond chips. Akhan Semiconductor Inc. is licensing the diamond semiconductor process from the U.S. Energy Department's Argonne National Laboratory to realise the promise of diamond semiconductors that have been known to be faster, use less power, and thinner and lighter weight than silicon. The startup may be making significant headway towards realising this potential.

Akhan Semiconductor has a 200mm wafer fab in Gurnee, Ill. and expects to announce a diamond semiconductor IC in a consumer product at the Consumer Electronics Shows (CES) 2017.

Since before 2000, Argonne National Lab has been experimenting with diamond chemical vapour deposition (CVD), spinning off Advanced Diamond Technologies Inc. who partnered with Innovative Micro Technology to produce diamond microelectromechanical systems (MEMS) and inspiring diamond wafer specialists like SP3 Diamond Technologies to create the CVD equipment to deposit perfect crystalline diamond.

So far, however, the biggest successes for diamond have been in jewellery, abrasives and other industrial uses of man-made diamonds. Nevertheless, Argonne National Labs continued pursuing the dream of diamond semiconductors by finding a way to make diamond, a natural insulator, into a semiconductor and a conductor laying out the path to all diamond chips.

Figure 1: Samples of diamond on silicon from Akhan. (Source: EE Times)

The biggest problem that kept diamond from being commercialised, until now, has been the ease of making p-type transistors, but the difficulty of making n-types, a problem solved by founder and CEO of Akhan Semiconductor, Adam Kahn, who dubbed his process the Miraj Diamond Platform. With both p- and n-type devices, diamond complementary metal oxide semiconductors (CMOS) are now possible. Akhan Semiconductor hopes to roll out the world's first CMOS-compatible diamond semiconductors.

"We recently demonstrated CMOS-compatible diamond semiconductors, with both p-type and n-type devices, by successfully fabricating diamond PIN [abbreviation for a p-type, intrinsic, undoped, n-type junction] diodes with a million-times better performance than silicon and one-thousand-times thinner," Khan said.

Its secret was co-implanting phosphorous in p-type devices and co-doping barium and lithium into n-type devices, resulting in tunable electronics that achieve comparable performance in both types, thus enabling diamond CMOS. The company's first demonstrated device, however, was a diamond PIN diode that was a record-breaking 500nm thin. This type of performance is due to diamond being a super wide band-gap material, wider than even silicon carbide and gallium nitride.

"Thermal analysis showed that there were no hot spots on our PIN either, so there were no parasitic losses like with silicon PIN diodes," Khan noted.

Khan has also demonstrated 100GHz devices by virtue of the ultra-low resistance of diamond, which can be deposited on silicon, glass, sapphire or metal substrates. Those kind of speeds could revitalise the processor races, which have been idled at 5GHz for a decade. With silicon, 5GHz is the limit, since their high power consumption and thermal hot-spots turn devices into soup, but diamond has 22 times the thermal conductivity of silicon and five-times that of copper, Kahn claimed.

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