Printing silicon at low temperatures

Silicon printed on paper. Credit: M. Trifunovic et al./Applied Physics Letters

Printed electronics is old story: it has been created several years ago and we have quite a number of applications for it. It is cheap and easy to manufacture requiring basically an ink-jet printer. The key is the ink: it has to be a solution that once printed can provide the characteristics you need for an electronic circuit. It has to provide conductivity, be able to create resistors and condenser and of course be able to create diodes and transistors. 

This has been done and we have seen RFID tags, antennas, sensors being printed. 

However, if you need speed, that is fast electronics like the one you are used in today’s chips printed electronics do not fit the bill. The inks used cannot compare to silicon.

Here is where this news from Delft University researchers comes in: using silicon ink to create silicon component.

The problem with silicon ink so far was that once it is printed it requires high temperature, 350° C, to be transformed into a polycrystalline form that can be used as an electronic circuit. 

This temperature kills the substrate, polymer, paper, fibers and makes printing impossible.

At Delft researchers have discovered an ingenious way of heating the printed circuit (as it is being printed, in such a way that the resulting temperature remains below 150°.

They use an excimer-laser (the same ones used to manufacture your smartphone display) to provide pulses no longer than a few tens of nanoseconds. This provided sufficient energy to transform the polysilene (the silicon ink) into polycrystalline silicon that can form the electronic circuit without overheating the substrate.

This can yield to much more effective printed electronics, fitting wearable sensors with embedded processing capability.  The process used is fit for manufacturing transistors in volume and at low cost, exactly what is needed for innovation.

Author - Roberto Saracco

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