Researchers at Intel, RTI International of North Carolina, and Arizona State University are working on ultrathin refrigerators for microprocessors. The technology uses a thermoelectric cooler and can target hot spots on chips, saving power and space. The work illustrates for the first time that it's possible to integrate thermoelectric material into chip packaging, making the technology more practical than ever before.
"People have been talking about using high-efficiency thermoelectric materials for cooling hot spots on chips for years," says Intel manager Ravi Prasher. He says that part of the reason he and his colleagues were able to succeed is because they used a material that has shown exceptional thermal properties, and they relied on Intel's knowledge of chip packaging to build an integrated thermoelectric system that was engineered to fit within the confines of a chip's housing.
To put the microrefrigerator in the chip package, the engineers integrated the cooler onto a square of copper, just like the type that's already used in chip packaging to disperse heat. Usually this piece of copper is in close contact with the chip, but the researchers put the 0.4-millimeter-square cooler in between the chip and the copper. When the microrefrigerator was turned on, it cooled a localized region on the chip by about 15 °C. This is significant, says Venkatasubramanian, because generally speaking, for each five-degree increase in chip temperature, there is a marked decrease in reliability and performance of a chip. In the demonstration, the researchers only used one microrefrigerating unit but foresee using three or four per chip, to cover the hottest areas.