90% of modern-day electronics – for example that found in computers and mobile phones – consists of billions of high-performance, ultralow power devices integrated onto tiny wafers made from rigid and brittle bulk monocrystalline (100) silicon, which is very cheap. The Saudi Arabia team, led by Muhammad Mustafa Hussain, has now developed a new generic low-cost regenerative batch fabrication process to transform these device-containing wafers into thin, mechanically flexible and optically transparent silicon “fabric”. The new process consists of a series of microfabrication steps that allows the researchers to peel off a thin top layer from a rigid silicon wafer on which devices have been fabricated. A subsequent polishing step prepares the remainder of the wafer so that it can be reprocessed to obtain more of this flexible fabric, so minimizing wafer waste.

The feat does not end there: the researchers say they followed industry-standard CMOS-compatible processes to build a variety of devices on their flexible wafers, including memory and logic, thermoelectric generators and micro lithium-ion batteries. After fabricating the devices, they identified the unused areas on the wafers, made trenches in these areas using reactive ion etching, added a protective insulating layer in the sidewalls of the trenches and then freed up the top portion (which was 10 µm thick) in the wafer using xenon difluoride-based gas reactions.

“After releasing the top portion of the wafer, we chemically and mechanically polished it to take out the bottom bulk portion of the substrate so that we could reuse it,” explained Hussain.

The team say that it is now busy making CMOS circuits, memories and communications systems on the flexible wafers that it has recovered. “We would also like to look at fabricating high-performance microprocessors, biomedical devices and augmented, smart, electronic-skin using the flexible films,” Hussain told nanotechweb.org.

The researchers detail their work in ACS Nano DOI: 10.1021/nn405475k.

Further reading

On the road to transparent, flexible computers (Sep 2013)
Flexible TEG breaks new power record (Dec 2013)