Massachusetts Institute of Technology (MIT) researchers claim to have made a breakthrough allowing the production of nano-scale patterns much smaller than the wavelength of light used to expose them.

The researchers say they have found a way of harnessing an etching method to create a mask with etch lines just 36 nanometers wide. They say they could place many such lines spaced a similar distance apart.

The novel method for etching extremely narrow lines on a microchip uses a material that can be switched from transparent to opaque—and vice versa—by exposing it to certain wavelengths of light.

Such materials are not new, the researchers admit. But what is new is that the mask produced by this method can be used to create a correspondingly fine line on the underlying material.

The new absorbance modulation technique makes it possible to create lines that are only about one-tenth as wide as the wavelength of light used to create them.

Researchers had to find a suitable photochromic material—one that changes its color, and therefore its transparency, in response to light—whose clear and opaque parts would remain stable after the initial exposure to light.

The researchers exposed the photochromic material to a pair of patterns, each of a different wavelength, simultaneously. When the bright lines at one wavelength coincide with the dark lines at the other wavelength, extremely narrow lines of clear material are formed interspersed with the opaque material.

This banded layer then serves as a mask through which the first wavelength illuminates a layer of material underneath, similarly to the way a photographic negative is used to make a print by shining light through it onto a sheet of photo paper underneath.

The research was carried out by research engineer Rajesh Menon of the Research Laboratory of Electronics and graduate students Trisha Andrew in the Department of Chemistry and Hsin-Yu Tsai in the Department of Electrical Engineering and Computer Science, and is reported in a paper published in the April 10 issue of Science.

The work was partly funded by grants from LumArray Inc., where Menon is co-founder, the MIT Deshpande Center for Technological Innovation and the Defense Advanced Research Projects Agency.

Menon expects the research to lead to commercial production within five years.

LumArray, on its website, briefly delves into its technology — Zone-Plate-Array Lithography—that integrates microfabrication, micromechanics and computing. The company's ultimate aim is to transfer a design drawn on a computer screen directly onto a substrate.

An earlier detailed technical paper on the technology was published here.

 Vasil Sidorov on 14.04.2009 After MIT News