IBM Scientists Effectively Eliminate Wear at the Nanoscale
(萌妹社区Org.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 atomic force microscopy to manipulate nanostructures and devices by scanning or rather sliding in very close proximity over the surface鈥攕imilar to the way the needle of a record player on a record. Today, these techniques鈥攊ncluding for example the well-known atomic force microscope鈥攁re 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鈥� 鈥渆yes鈥�, 鈥渆ars鈥�, 鈥渘ose鈥�, and 鈥渉ands鈥� 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 silicon wafers approach physical limitations for critical chip layers.
鈥淐ontinued 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,鈥� 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鈥攎easuring just five nanometers at its apex鈥攖his problem is accentuated. A few cubic nanometers more or less can ruin the sensitivity of the tip. 鈥淚n 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,鈥� explains IBM scientist Mark Lantz. In the currently used scanning modes, the tip wears out after a few meters or yards. 鈥淢oreover, in addition to causing wear of the tip, friction can potentially also do damage to the surface being characterized.鈥�
In their paper, published in the September issue of Nature 萌妹社区, IBM scientists solve this challenge by 鈥渄emonstrating 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.鈥� By applying an AC voltage between the cantilever鈥攖he mechanical arms on which the tips are attached and over which they are controlled鈥攁nd 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. 鈥淭hough vanishingly small, it is this vibration that greatly reduces friction and 鈥渆ffectively鈥� eliminates鈥攖o below the detection limit corresponding to the remarkable low number of losing one atom per meter鈥攖ip wear under experimental conditions,鈥� 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 鈥淒ynamic Superlubricity and the Elimination of Wear on the Nanoscale鈥� by M.A. Lantz, D. Wiesmann, and B. Gotsmann, is published in Nature 萌妹社区, Volume 4, Issue 9 (September 2009).
Provided by IBM
