The microchips inside smartphones and computers are getting denser: billions of transistors are packed onto a sliver of silicon the size of a fingernail. When they work, they give off heat like tiny stoves. If that heat isn't drawn away, the chip overheats, starts glitching, or fails outright. Engineers are on the hunt for materials that can be laid down in a thin layer over the circuitry to carry heat off without messing with the electrical signals.
One candidate is aluminum nitride, a compound of aluminum and nitrogen. It doesn't conduct electricity, but it's a great heat conductor. The catch is that the different layers of a microchip are made of different materials: silicon, silicon oxide, silicon nitride, aluminum oxide. Would the film dissipate heat equally well on each of them? The researchers deposited aluminum nitride films 600 and 1200 nanometers thick onto all four substrates. A thickness of 600 nanometers is about a hundred times thinner than a human hair.
To see the practical benefit, the scientists built a computer model of a transistor covered with an aluminum nitride film. It turned out that the peak temperature inside the device drops by 44%. A transistor with the film runs cooler, like a person wearing a light windbreaker instead of a fur coat on a warm day.
This approach paves the way for more powerful and reliable chips for phones, computers, and servers. The heat that used to build up inside now escapes through the thin film, like steam from a pot through a slightly open lid.
Aluminum nitride is used in ultraviolet LEDs: it's transparent to those rays and efficiently draws heat away from the crystal.