PORTLAND, Ore. IBM Research has demonstrated a 3-D technique for patterning at the atomic scale that it says outperforms e-beam lithography in speed and resolution, at lower cost. For the demo, researchers fabricated a 22 x 11-micron map of Earth and a 25-micron-high 3-D rendering of the 14,692-foot-tall Matterhorn.
The tiny images, representing a scale of 5 billion to 1, were created in less than 3 minutes with a silicon tip similar those used in atomic-force microscopes, but measuring just 500 nanometers in length and only a few nanometers wide at its apex. The tip was attached to a flexible cantilever that IBM says can scan the surface of any substrate with 1-nm accuracy.
The company plans to use the patterning technique for prototyping nanoscale CMOS electronics, optical components and meta-materials and for making shape-matching templates that direct the self-assembly of nanorods or nanotubes.
IBM's setup operates like a nanoscale milling machine; by applying heat and force to the tip, any nanoscale pattern can be etched into substrate materials. The researchers modulated the force and heat to create the images by removing unwanted layers the way a sculptor removes stone from a statue; the Matterhorn rendering, for example, required the removal of 120 layers to reveal the 3-D image of the famous Alpine peak.
The new patterning technique currently has a resolution of about 15 nm—about twice as small as e-beam lithography—and potentially could go even smaller. The patterning device costs from one-fifth to one-tenth the price of e-beam lithography and is much faster, according to the researchers.
Thus far IBM has demonstrated the technique on two substrate materials: a polymer called polyphthalaldehyde, developed by IBM fellow Hiroshi Ito in the 1980s, and a molecular glass similar to conventional resists.
Molecular glass was proposed as a resist material by Mitsuru Ueda of Japan's Yamagata University in the late 1990s, and more recently has been tried for high-resolution photoresists by Chris Ober at Cornell University.
A tip temperature of 626°F was needed to break the hydrogen bonds that hold the molecular glass to the surface, IBM reported.