This is Science: Silicon Electronics: Bend Me All the Way

Today it seems that modern electronics are something monolithic, solid, but not far from the day and hour when electronic devices become flexible (and some manufacturers have already succeeded!), Smartphones can be rolled up, and a 2-meter monitor will automatically “Roll out” when you turn on the TV or computer ... This, of course, is still a dream, but real flexible electronics are already being produced in laboratories around the world as prototypes for finding the most optimal and cheap technology.



The topic of creating flexible non-carbon, namely silicon electronics, prompted developers from the King Abdula Institute of Science and Technology that in Saudi Arabia (yes, oil is not an obstacle to progress), to develop a new method for transferring microelectronic components such as capacitors, transistors, and whole microchips onto a flexible substrate of silicon dioxide or polycrystalline / amorphous silicon.

Of course, the solution to this issue is not new, and many laboratories have already done considerable work in this field. For example, IBM introduced its vision of flexible electronics a year ago ; before that, a lot of attempts were made to create “spring-loaded” contacts , to fasten separate, small chips on ordinary silicon with conductive polymers, and eventhe solution is based on carbon nanotubes , however, the technology described below requires only a small change in the manufacturing processes and uses silicon and silicon dioxide.

So, few probably know that ordinary glass can be bent almost in half, the whole thing is only in the thickness of the product. This is actually the same as comparing aluminum or iron thin foil with a bulk piece of metal. So the technology presented uses this effect, that is, the thickness of the substrate is reduced to only 5 microns. To separate the substrate from the carrier, holes of about 3-5 micrometers in size are "drilled" in it, through which reaction etching then occurs with uniform separation of the substrate from the carrier.


Two processes for creating flexible electronics: a) on a transparent silicon dioxide substrate and b) on a conventional silicon substrate.

To test the operability and reproducibility of this process, the authors created flexible semiconductor capacitors (MOSCAP), field effect transistors ( MOSFET ), and metal-type capacitors metal insulator (MIMCAP). All test samples confidently bend and demonstrate almost indistinguishable characteristics compared to bulk counterparts.


Capacitors and field effect transistors, created on a thin and flexible silicon wafer.

But this is not all, the work also presents the work of finished devices such as a micro-Li-Ion battery and a thermoelectric generator:


Demonstration of the operation of real devices: ab) thermoelectric generator and its characteristics ©, d) lithium battery and its capacity (e)

Speaking of cost, the authors write that all the processes involved in the manufacture are equivalent to those used in ordinary production, with the exception of one - reactive etching using XeF ₂ followed by separation of the plate. However, about 18 g of the compound is consumed per 18 cm ² plate (100 cycles, 30 s / cycle). Given the cost of $ 8 / g, it turns out that the entire etching procedure comes out at $ 0.88 / cm ² , which is not so small. And the recovery of Xe - at least in part - will reduce costs many times over. In addition, thinning the substrate will significantly save materials.

And finally, a video in which the authors are “played” with a 4 inch plate, which can be taken here .

Original article published in ACSNano magazine .

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