One of Europe’s largest micro- and nano-conferences: the Micro- and Nano-Engineering 2007 took place in Copenhagen from September 23rd to 26th.
By: Jakob Kjelstrup-Hansen, jkh@mci.sdu.dk
One of the keynote presentations was given by Yan Borodovsky,
who is Senior Fellow and Director of Advanced Lithography at Intel
Corporation. In his talk, he was addressing some of the challenges
faced by lithography due the continued downscaling of transistor
dimensions on integrated circuits as dictated by Moore’s law. This
states that the number of transistors on an integrated circuit doubles
every second year. Today, patterning is done by UV lithography using a
wavelength of 193 nm. Patterning the 45 nm node and the future 32 nm
node at this wavelength requires some innovative solutions as
diffraction effects have a significant, negative effect on the
achievable resolution. One of the hot topics within the lithography
community today is the use of immersion lithography, in which the gap
between the final lens of the exposure system and the photo resist does
not contain air but water. Since water has a higher refractive index,
light can be focused even further thereby allowing an improved
resolution. However, immersion lithography still suffers from a much
higher defect density than conventional ‘dry’ lithography and therefore
a reduced yield. So while most of Intel’s competitors have switched to
immersion lithography, Intel is staying with dry lithography for their
45 nm node and makes use of other tricks such as double patterning
(using two masks for the same resist) to achieve the desired line width.
Michael Roukes, who is Professor of Physics, Applied Physics,
and Bioengineering at the Kavli Nanoscience Institute at Caltech, and
who is one of the pioneers of NEMS (NanoElectroMechanical Systems) gave
an inspiring talk on the future directions of nanotechnology in general
and NEMS in particular. In their ultimate design, NEMS will be
constructed from molecular-scale mechanical elements as predicted by
Feynman in his famous “Plenty of room at the bottom” speech. According
to Roukes, however, a large part of today’s nanotechnology is not
really technology but rather “nanocraft”. Typically, only one nanotube
or nanowire device is made to demonstrate the functionality, but since
the parts do not really fit together, each device requires hours and
hours of tweaking and fitting – more of an art or craft than a
technology. He compared to the work of Charles Babbage (1791 - 1871),
an English mathematician and mechanical engineer, who had the original
idea of a programmable computer that could solve complicated
mathematical problems. Babbage’s vision - a huge mechanical machine -
was, however, not realized in his time due to the lack of precision
engineering, but it was built by the London Science Museum in 1991
functioning perfectly doing calculations to seven significant figures.
Roukes’ point was that if we wish to fulfill the vision of Feynman, we
need to move towards more standardized mass fabrication methods – also
for NEMS. Recently, Roukes started collaborating with the LETI-Minatec
center in Grenoble on the fabrication of nanomechanical sensors for
biochemical analysis on 8 inch wafers for true VLSI of NEMS. From his
own research, Roukes showed some recent results on nanomechanical gas
sensing at room temperature and at atmospheric pressure reaching an
amazing mass sensitivity around 100 zg (zepto = 10-21).
Apart from these fascinating talks, there were plenty of other
interesting presentations. Nanoimprint lithography in particular was
brought up again and again with its appealing characteristics on
enabling patterning on the nanoscale over large areas at a relatively
modest cost – it definitely seems like a technology that will make an
impact!
05.10.2009
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