Diamond Thermal Conductivity: A New Era in Chip Cooling

Summary:

> Rather than allowing heat to build up, what if we could spread it out right from the start, inside the chip?... To do that, we’d have to introduce a highly thermally conductive material inside the IC, mere nanometers from the transistors, without messing up any of their very precise and sensitive properties. Enter an unexpected material—diamond.

> ... my research group at Stanford University has managed what seemed impossible. We can now grow a form of diamond suitable for spreading heat, directly atop semiconductor devices at low enough temperatures that even the most delicate interconnects inside advanced chips will survive... Our diamonds are a polycrystalline coating no more than a couple of micrometers thick.

> The potential benefits could be huge. In some of our earliest gallium-nitride radio-frequency transistors, the addition of diamond dropped the device temperature by more than 50 °C.

Fifty Celsius is an insane drop.

It sounds like the most important part of the article (and another cool quote) is this:

>Until recently we knew how to grow it only at circuit-slagging temperatures in excess of 1,000 °C.

So basically, the big breakthrough was low-temp growth of a diamond lattice. Very cool they can do it at such a low temperature. It must be a crazy low temp - probably under 100C?

From the article:

"we were able to find a formula that produced coatings of large-grained polycrystalline diamond all around devices at 400 °C, which is a survivable temperature for CMOS circuits and other devices."

It is genuinely impressive to grow thin film polycrystalline diamond at 400C, but my understanding is this temperature is basically at the ceiling of what the circuits will tolerate in the course of manufacturing to still get a good quality device at end of line. Stress tests, anneals, and wafer bakes are usually limited to about 400C - unless the point is to deliberately degrade the chip

Not to say that it can't be done, only that the process window is not very large and the propensity for deleterious carbon soot is very high. Likely this will generate some very fun, highly integrated problem statements before we see this available for sale.

Getting heat out of the chip is such a painful and important struggle. I hope this works on a real process line. Too many benefits on the table to ignore.

Edit: Grammar, clarity