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nanotimes News in Brief

Mass Production // Top-down Unmanufacturability

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n a paper published in Nanotechnology, Professor Mike Kelly, Centre for Advanced Photonics and

Electronics, University of Cambridge, U.K., sta- ted that you cannot mass produce structures with a diameter of three nanometres or less using a top-down approach. This statement raises a major question concerning the billions of dollars that are poured into nanotechnology each year in the hope that the latest technology developed in the lab can make the transition to a manufactured product on the market.

The overall goal when entering nanotechnologies into the market is low-cost, high-volume manufac- turability, but at the same time, the materials’ pro- perties must be highly reproducible within a pre-spe- cified limit, which Kelly states cannot happen below the 3nm limit when trying to make arrays. The top- down approach to manufacturing, which Kelly states is limited, uses external tools to cut and shape large materials to contain many smaller features. Its alter- native, the bottom-up approach, involves piecing together small units, usually molecules, to construct whole materials – much like a jigsaw puzzle – howe- ver this process is too unpredictable for defect – free mass production of arrays.

Kelly used statistical evaluation of vertical nano- pillars – that have been suggested for uses in sensors and displays – as an example to demonstrate his theory. He states that the proof comes in two stages.

The first is due to the fact that when materials are mass produced on such a small scale there will be a lot of variation in the size of different components.

As a result of this variation, the properties of the material will vary to an extent where the material cannot function to full capacity within an array.

Professor Kelly says, “If I am wrong, and a counterex- ample to my theorem is provided, many scientists would be more secure in their continued working, and that is good for science. “If more work is de- voted to the hard problem of understanding just what can be manufactured and how, at the expense of more studies of things that cannot be manufac- tured under the conditions of the present theorem, then that too is good for science and for technology.”

M. J. Kelly: Intrinsic top-down unmanufacturability, In: Nanotechnology, Volume 22(2011), Number 24, Article 245303, DOI:10.1088/0957-4484/22/24/245303: http://dx.doi.org/10.1088/0957-4484/22/24/245303

Abstract: “(...). We show that structures with 3 nm design rules can be fabricated but not manufactured in a top-down ap- proach – they do not have the reproducibility to give a satisfactory yield to a pre-ordained specification. It is also shown that the transition from manufacturability to intrin- sic unmanufacturability takes place at nearer 7nm design rules.” © IOP

11-04 :: April/May 2011