Lithography is clearly a challenge (and not the only one)and at least it seems that it will need more time.Monolithic 3D with thin layers is an excellent path to continue Moore's Law. There are area that would need engineering such as heat removal and crosstalk but there are no "Red Brick Wall". And as the NAND vendors already adapting monolithic 3D for future scaling, there will be less vendors to support the escalating costs of dimensional scaling for lithography, transistors development etc.
The advantage of monolithic 3D scaling that we could apply it to an older process yet achieve better benefits than the next node of dimensional scaling. I would expect that the 28nm or 20nm would be a good node to apply monolithic 3D as an alternative to 14nm or 10nm
Monolithic 3D is by far the best way to keep on integration while not increasing the overall power consumption. As for heat removal/thermal consideration, it is not much different than dimensional scaling as the monolithic scaling utilize very thin layers. In fact a detail paper on this issue resulted of a joint work with research group at Stanford university will be presented in the coming IEDM 2012
DSA is promising but a long road to become production worthy. It becomes more sensitive in Photoresist thickness, temperature and chemical variations. It usually is treated as alternative if EUV or multi patterning fails to meet market requirements.
The dimensional scaling is clearly reaching demising return and escalating challenges. The NV NAND vendor have recognized it and are shifting to monolithic 3D (see Blog piece by Israel Beinglass http://www.monolithic3d.com/2/post/2012/10/3d-nand-opens-the-door-for-monolithic-3d.html)
The logic vendor would sooner or later recognize it too (especially as the would need to carry the burden all by themselves)- the future of scaling is up - monolithic 3D
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