PLASTIC CHIPS

ARM builds a flexible SoC

INTEGRATED CIRCUITS have been constructed on a silicon substrate since their inception (we even use the word silicon as a synonym for chips), but ARM has been working on using plastic as a substrate for about ten years. Simple electric circuits on flexible plastic are nothing new; paint a design in conductive ink, and you’re done. There’s one in every membrane keyboard and RFID sticker.

Researchers at ARM and PragmatIC have managed to put a fully-functional SoC on a flexible plastic substrate. It is essentially a Cortex M0 microcontroller. The PlasticARM (great name) carries 128bytes of RAM, 456bytes of ROM, and a Cortex M0 core that supports 32-bit ARM microarchitecture. The plastic component is a polyimide, and the transistors are thin metal oxide. It’s made using a hybrid mix of a traditional photolithography process, and specialist printing. There are 13 material layers, with four metallic layers, totaling 18,000 logic gates in all.

The regular silicon Cortex M0 is built by TSMC on a 90nm process, and fractions of a square millimeter, the plastic version is just under 60. It’s also slower than the original, running at kilohertz rather than megahertz. Energy efficiency isn’t good either, as it loses a lot to static. Currently, it can only run programs hard-wired into it, but re-writable memory is coming. This isn’t a rival to traditional silicon as such, but rather a chip for simple, mundane, or novel applications, where power and speed limitations aren’t an issue.

There are no specific plans for the PlasticARM just yet, however, the goal is to make plastic chips cheap enough to be disposable. Eventually, they will be priced in cents rather than dollars and printed in their billions. Then you can have chips on anything, and everything.