Holey Silicon Is Way Cool


Overheating in electronic designs and equipment has always been a major concern and, with ever-rising miniaturization, keeping things cool has become a top priority. Well, scientists at the University of California, Irvine, claim to have made a breakthrough with a new material configuration to facilitate cooling. They herald the attributes of holey silicon, a computer chip wafer with tiny, vertically etched orifices that shuttle heat to desired locations.


Jaeho Lee, UCI assistant professor of mechanical & aerospace engineering, says “We found that heat prefers to travel vertically through but not laterally across holey silicon, which means the material can effectively move the heat from local hot spots to on-chip cooling systems in the vertical direction while sustaining the necessary temperature gradient for thermoelectric junctions in the lateral direction.”


Jaeho Lee, UCI assistant professor of mechanical & aerospace engineering, believes that holey silicon – microchip material vertically etched with nanoscale orifices – might be a breakthrough in the quest to keep modern electronics cool.


The researchers demonstrated the cooling effectiveness of holey silicon is at least 400% better than chalcogenides, compounds commonly used in thermoelectric cooling devices. The holey silicon research is a follow-up to a study published in Nature Communications in early 2017 in which Lee, as lead author, and his UC Berkeley-based collaborators employed nanometer-scale silicon mesh material to investigate properties of phonons, quasiparticles that give scientists insight into thermal transport mechanisms. Knowledge gained from this earlier study helped the team understand how small, neck-shaped structures created by the etched holes in holey silicon cause phonon backscattering, a particle effect leading to low in-plane thermal conductivity. High cross-plane thermal conductivity was caused by long-wavelength phonons that help to move heat away.


According to Lee, the temperature problem in electronics has grown in the past few years as microchip designers seem to have reached a size boundary. With larger components, manufacturers can use heat sinks, fins and even fans to funnel warmth away from critical hardware. On today’s densely packed chips, there’s no room for traditional cooling technologies.


 Other are longevity and reliability. Semiconductor chips are finding more unique applications such as acting as sensors and actuators. These devices are expected to run continuously for years and even decades. Prolonged exposure to heat will cause the failure of such infrastructure. Lee sums it up concisely, “It’s important that we continue to develop a better understanding of the fundamentals of thermal transport and find ways to control heat transfer at the nanoscale.”


For more info, visit UCI’s Nano Thermal Energy Research Group.