IBM Scientists Effectively Eliminate Wear at the Nanoscale

Sep 07, 2009

(PhysOrg.com) -- IBM scientists have demonstrated a promising and practical method that effectively eliminates the mechanical wear in the nanometer-sharp tips used in scanning probe-based techniques. This discovery can potentially be used in the development of next generation, more advanced computer chips that have higher performance and smaller feature sizes. Scanning probe-based tools could be one approach to extend the capabilities, quality and precision beyond the projected limits of current production and characterization tools.

Scanning probe-based techniques utilize tiny, nanometer-sharp tips borrowed from to manipulate nanostructures and devices by scanning or rather sliding in very close proximity over the surface—similar to the way the needle of a record player on a record. Today, these techniques—including for example the well-known atomic force microscope—are established tools for scientists to explore the nanocosmos. Scanning-probe techniques today allow for the highest possible resolution down to the atomic or molecular scale and represent essentially the scientists’ “eyes”, “ears”, “nose”, and “hands” as they explore the smallest objects known to mankind.

In the semiconductor industry, these techniques due to their atomic resolution and manipulation capabilities become increasingly attractive for use in the development and manufacturing of next generation chips with ultra-small feature sizes. While small by most standards, today's 40 nm transistors can still shrink further, but it becomes increasingly challenging and costly since the current tools and methods to develop and process the chips out of approach physical limitations for critical chip layers.

“Continued scaling to further increase device performance will require new device architectures, smaller feature sizes and new materials. Tools based on scanning probe technology could become essential for the metrology of future technology nodes as well as for the development, fabrication and characterization of novel nanoscale devices,” says IBM Fellow Evangelos Eleftheriou of IBM Research - Zurich.

A key limiting factor for the prospects of large-scale industrial uses of such techniques, however, has been mechanical wear of the sharp tips. Wear resulting from friction between moving parts are inherent to all mechanical processes on the macro- as well as on the nanometer-scale. However, for scanning probe-based technologies, which rely on a nanometer-sharp tip—measuring just five nanometers at its apex—this problem is accentuated. A few cubic nanometers more or less can ruin the sensitivity of the tip. “In future industrial applications such as large area characterization of the features on a silicon wafer, a tip would need to be able to slide tens of kilometers or miles without replacement,” explains IBM scientist Mark Lantz. In the currently used scanning modes, the tip wears out after a few meters or yards. “Moreover, in addition to causing wear of the tip, friction can potentially also do damage to the surface being characterized.”

In their paper, published in the September issue of Nature Nanotechnology, IBM scientists solve this challenge by “demonstrating the effective elimination of wear on a tip sliding on a polymer surface over a distance of 750 meters by modulating the force acting on the tip-sample contact.” By applying an AC voltage between the cantilever—the mechanical arms on which the tips are attached and over which they are controlled—and the sample surface, the cantilever can be excited at high frequencies of one Megahertz. The cantilever bends and the tip vibrates with an almost imperceptible estimated amplitude of one nanometer. “Though vanishingly small, it is this vibration that greatly reduces friction and “effectively” eliminates—to below the detection limit corresponding to the remarkable low number of losing one atom per meter—tip wear under experimental conditions,” states Bernd Gotsmann of IBM Research - Zurich. After the 750-meter wear test, which took a week of continuous operation, the tip was still operating flawlessly.

With the wear problem tackled, researchers at IBM Research - Zurich are now investigating a number of possible applications of scanning probe-based technologies including nanofabrication, nanolithography and high-speed metrology. Operating a large number of tips in parallel would enable, high-throughput, high-speed, automated metrology systems for potential use in chip development and manufacturing. Such metrology systems could characterize device dimensions or identify defects on the structured silicon wafers with much higher precision and accuracy and potentially lower cost than currently available tools. Scientists at IBM Research - Zurich are also investigating powerful scanning probe-based method for high speed patterning of complex two and three-dimensional nanoscale structures.

More information: The scientific paper entitled “Dynamic Superlubricity and the Elimination of Wear on the Nanoscale” by M.A. Lantz, D. Wiesmann, and B. Gotsmann, is published in Nature Nanotechnology, Volume 4, Issue 9 (September 2009).

Provided by IBM

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Fazer
4 / 5 (4) Sep 07, 2009
Cool. It has always amazed me how adding vibration or noise to a system (such as adding dither to digital audio or imagery) can smooth things out.

Someone suggested once that the "noise" of speculation on the stock market tends to smooth things out and help "settle out" the best prices for commodities, in direct contrast to those who say that speculation is bad and leads to market bubbles.

It makes you wonder how many other systems would benifit from noise. For example, is there some way to "vibrate" a power cable so that the electrons traveling on the surfaces of the copper encounter less collisions, and thus less resistance? I don't mean physically vibrating the cable, but some other effect, like smaller AC waves hidden inside the big 60hz swings that do all the work. Say 1Ghz pulses at much lower amplitude.

Maybe social agitation is a good thing, too.

Maybe it smooths things out and prevents people from exercising too much restraint, when faced with difficult, community-wide situtaions, until they reach a breaking point and start going postal.

Maybe I should just shut up and stop speculating?
poi
not rated yet Sep 07, 2009
Maybe I should just shut up and stop speculating?

lol! No, please, do continue. But remember the proportion, 1nm amplitude to 5nm width.
AlIIII
4.5 / 5 (2) Sep 08, 2009
Testing is improbable.
AlIIII
not rated yet Sep 08, 2009
vibration is just illussion to make the eye happy, with a perfect line.
RayCherry
3.7 / 5 (3) Sep 08, 2009
Fazer: Reminds me of the Japonese idea of avoiding earthquakes by regularly setting off controlled explosions, or simulated lightning strikes, along fault lines. The 'noise' causes the fault to vibrate more frequently, releasing some of the pressure that would otherwise contribute to quakes.

Perhaps the noise from the Metro systems of Lisbon and NewYork are creating similar localised effects.

As for the tips in the article, I'm sure that the vibration must occassionally have an adverse effect, but if the overall result is productive then it is an interesting solution
guiding_light
5 / 5 (3) Sep 08, 2009
I think the idea here is that constant contact or stress is to be avoided, in this case by oscillating so that contact only takes place part of the sampling time. By itself, the noise creates other concerns. Basically you want to watch out for other vibrations at the same frequency.
moj85
not rated yet Sep 08, 2009
interesting to think about this..
the human eye does the same thing. When we think we're "focused" on a single point, our eyes are actually moving very tiny amounts and quickly in that one area (called microsaccades) in order to continually provide information to the retina.

Very cool stuff.
brentrobot
not rated yet Sep 10, 2009
hmmm, I wonder if the lower friction will allow them to scan at a much higher velocity? Take the vibrations up to 10 MHz and also scan at 10x normal.