Spin-coated chips

IBM researchers have developed a process to make thin films of semiconducting materials that allows electrical charges to move through them about 10 times more easily than other similar approaches.

While traditional silicon semiconductor devices are increasingly smaller and more complex, they’re also becoming more expensive and difficult to manufacture.

As a result, silicon chips are often too costly for many simple applications. Researchers are therefore seeking new ways to make massive quantities of inexpensive, relatively basic semiconductor devices.

A breakthrough by a team at IBM’s T.J. Watson Research Center in Yorktown Height, NY, is claimed to be a big step in that direction.

Headed by David Mitzi, the team developed a simple, low-cost process to make extraordinarily thin films of semiconducting materials that allows electrical charges to move through them about 10 times more easily than other similar approaches.

‘These types of easily processed semiconducting films could eventually be used to make circuitry for very-low-cost or flexible displays, high-performance smart cards, sensors and solar cells or for flexible electronics coated onto a wide variety of moulded or plastic shapes,’ said Mitzi.

One of the simplest and cheapest alternatives to traditional silicon chip circuit manufacturing is spin coating. In spin coating, several drops of a liquid solution are simply placed onto a spinning platter in a high-tech version of a carnival paint spinner. Centripetal force spreads the liquid to a uniform thickness over the entire surface. The liquid is then cured into a solid thin film upon which transistors and other various electronic devices can be made.

Until now, semiconducting materials made using spin coating had limited usefulness because their circuits operated too slowly. And better semiconductors couldn’t be dissolved in any liquid that would result in a film thin enough to allow better circuit speed or ‘charge mobility.’

Mitzi’s team developed a way to dissolve higher-mobility materials in a liquid that could be used in a spin-coating process, leaving a very uniform film. A transistor made on the films was10 times faster than the charge mobility of any previously spin-coated semiconductor.

One drawback to the process is that it uses a highly toxic solvent to dissolve the semiconductor materials. But Mitzi is confident that alternative solvents will also work.

And the team believes its approach can be applied beyond spin coating to other fast and inexpensive ‘solution processing’ techniques such as printing, stamping, nanoimprinting, inkjet printing and dipping.

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