One thing that has changed in the year since the last ITF in Antwerp is that the industry has, at last, entered the era of extreme ultraviolet (EUV) lithography, something that IMEC has helped pioneer for nearly two decades. "For 7nm and 5nm it is clear that EUV lithography will be the main innovation. But to get below 5nm, to achieve the density improvement there is now a strong focus on the back end," said van den Hove. "With things like [FinFET] track reduction on the design side, the very aggressive scaling of gate pitch is a bit relieved.
The next question is: which of the various proposed followers to the FinFET will make it to mainstream production and when? "The FinFET extends certainly to 5nm and maybe below. The challenge for FinFET is the short channel effects and really that needs a gate-all-around [GAA] structure. However, we now think 3nm is less likely to need GAA because metal pitch is scaling more aggressively than gate pitch."
The ultimate design scaling is when there is just one fin per transistor and this is the moment when multiple nanowires or nanosheets will come in, Van den hove said. That is an option for 3nm and IMEC presented a paper on that at IEDM 2017. The nanosheet is basically a flattened or widened version of the nanowire with the ability to carry more current than a nanowire, said Van den hove. The next extension of that development is the complementary FET or CFET in which a single fin may carry p- and n-type the nanowires/nanosheets to create a compact support for CMOS logic.
And in terms of materials van den Hove said things are likely to remain with the status quo at least for logic processes. "Silicon-germanium is in use now. Inserting III-V materials is so much more difficult at least for logic. We are pursuing this kind of model but for more RF performance," he said.
The ITF will cover just about everything from the deepest technology roadmaps up to varied applications in smart cities and IoT. This year there is also a break out session on the business side of scaling technology from an initial experimental setting into a global business. In short the ITF will be discussing both the future of nanotechnology and, because of technology's impact, the future of society.
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