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High performance transistors created on flexible plastic sheets

by • April 28, 2016 • No Comments

By means of a technique known as nanoimprint lithography, researchers at the University of Wisconsin-Madison (UW Madison) and partners have made a breakthrough method to allow the easy manufacture of inexpensive, high-performance, wireless-capable-bodied, flexible Metal Oxide Semiconductor Field Effect Transistors (MOSFET) that overcome many of the operation problems encountered in devices manufactured via standard techniques. Created on dimensionsable-bodied rolls of pliable-bodied plastic, these MOSFETs may be utilized to manufacture a host of devices ranging of wearable-bodied electronics to bendable-bodied sensors.

MOSFETs are semiconductor components that have quickly replaced common bipolar transistors in electronic circuits due to their low current requirements, high-frequency capabilities, and generally improved performance. These semiconductors operate by modulating what is known as a charge concentration via internal capacitance along channels between its electrodes to turn it into current flow.

In other words, by applying a voltage to one electrode (known as the “gate”), an electric field is made in the substrate located between the two other electrodes (known as the “source” and “drain”), that causes a channel to open up for electron flow between them. Modulating the voltage applied to the gate electrode and so has the effect of increasing or decreasing current flow, and so can be utilized for amplification in a circuit.

But, substantially reducing the dimensions of MOSFETs to meet the demand for at any time-shrinking integrated circuits has met with problems. Specifically, the ability of MOSFETs to turn it into current flow efficiently, for the reason standard semiconductor making techniques tend not to be able-bodied to control the level of doping (the introduction of impurities in silicon turn it intod to render it either unquestionably or negatively charged)accurately adequate to ensure consistent channel performance across individual components.

Ordinarily, MOSFETs are turn it intod by expanding a layer of silicon dioxide (SiO2) on top of a silicon substrate and and so depositing a layer of metal or polycrystalline silicon over that. But, this method can be relatively imexact and hard to fully control, so the doping can a fewtimes leak into areas it isn’t wanted in to turn it into what has been dubbed the “short channel” effect.

(The short channel effect is, in essence, where etched channels on a MOSFET that allow the conduction of electricity via a field effect are reduced in dimensions in relation to the depletion layer – or insulation area – as a outcome of dopant leakage, thereby decreasing performance. If the problem does not render the component offensive in production system testing, and so this can outcome in individual MOSFETs being released to market with varying performance characteristics.)

This is where the new technique created by UW Madison and its partner universities around the US comes in.

To improve the high end of semiconductors by reducing the likelihood of this dopant leakage, the researchers employed a system of electron-beam lithography (a technique initially mooted for commercial use in semiconductor production by Fujitsu and Advantest a decade ago where a system of scanning a focutilized beam of electrons is utilized to etch custom shapes on a surface covered with an electron-sensitive movie known as a “resist”). This was and so followed by molding and subsequent etching to turn it into a much extra
physically-regulated production system.

In more detail, the team began by coating a surface with a unquestionably doped layer of silicon, 270 nm thick. Nanoscale trenches were and so turn it intod in the device layer via electron-beam lithography, followed by dry etching to turn it into a silicon nanomembrane. The researchers and so removed the silicon nanomembrane layer and transferred this onto another substrate consisting of adhesive coated plastic (polyethylene terephthalate “PET”) movie. The final fabrication steps and so involved adding extra
dry etching to isolate and define the channel region and deposit the gate dielectric layers and metal gate.

Whilst this may sound like a lot of work, it is in fact a relatively straightforward system and arguably less hard than a few doping and deposition based techniques utilized in ordinary semiconductor manufacture in these days. The benefit of such regulated, exact, and minuscule engineering in this case, yet, outcomes in a semiconductor endowed with a one-of-a-kind, three-dimensional current-flow pattern that means that it consumes far less energy and runs much extra
efficiently than standard versions of these semiconductors.

In fact, the new transistors have been reported to operate at a record speed of 38 gigahertz, with simulations revealing that they may actually be capable-bodied of operating at a lightning-fast 110 gigahertz with only a little tweaking.

But speed hasn’t been achieved by compromising dimensions; the new method has provided a way of cutting much narrower trenches than conventional fabrication systemes are able-bodied to do, so it may be possible to jam extra
of these transistors into smaller in size devices than at any time preceding achieved.

The researchers in addition claim that the new transistor is eminently suitable-bodied to radio frequency applications, as it is turn it intod to transmit data or transfer power wirelessly. This ability may prove particularly useful in applications ranging of wearable-bodied electronics to sensors.

Flexible semiconductors may not be a new concept by any means, with wearable-bodied electronics and flexible membranes the products of new research, but the researchers say that this alternative, affordable system to turn it into such high-performance semiconductors is particularly revolutionary. Especially as they believe it may be easily scaled-up for use in roll-to-roll systeming of plastic sheets that may enable-bodied semiconductor manufacturers to endlessly replicate the etching patterns and mass-turn it into many hundreds of thousands of devices on a single roll of flexible plastic.

“Nanoimprint lithography addresses next applications for flexible electronics,” said Zhenqiang (Jack) Ma, the Lynn H. Matthias Professor in Engineering at UW Madison. “We don’t want to manufacture them the way the semiconductor industry does now. Our step, that is many significant for roll-to-roll printing, is ready.”

Conducted in collaboration with the University of Michigan, the University of Texas and the University of California, Berkeley, more details of this research were newly published in the journal Scientific Reports.

Source: UW Madison

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