Cooler Semis

Last December's Editor Notes outlined research from the University of Michigan regarding microfluidic channels on a semiconductor impregnated with living cells that could be switched on/off, yielding a chip that would replace animals and humans in medical tests. As one discovery leads to another, similar technology is emerging at the Georgia Institute of Technology, however with a different goal: keeping semis cool.

Georgia Tech Researchers describe a technique for fabricating microfluidic cooling channels on the backs of ICs to eliminate heat sinks and other cooling components. This is a low-temperature technique—less than 260°C—that assembles cooling channels without damaging the wafer.

Researchers etch trenches deeper than 100 µm on the back of a chip, then coat it with a layer of sacrificial polymer, which fills the trenches. After a polishing step, the trenches get a porous overcoat and the chip undergoes heating, which causes the polymer to decompose, leaving microfluidic channels in the coating. A final polymer layer is applied to make the system watertight.

The microchannels can withstand pressure in excess of 35 psi and the system should be able to cool 100W per square centimeter using buffered de-ionized water as a coolant. Circulation is via a micro pump or a central circulation system.

According to graduate research assistant Bing Dang, "This scheme offers a simple and compact solution to transfer cooling into a Gigascale chip, and it's compatible with flip-chip packaging." As heat is the enemy of all things electronic, this technology should raise a few industry eyebrows. If so, future semiconductors will be 'way' cool. For more details, contact Bing Dang at (404) 894-9910 or [email protected].

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