NIST: NIL actually improves nanoporous layers

Apr. 30, 2008 – NIST says its work has helped resolve whether nanoimprint lithography (NIL) can accurately stamp delicate insulating structures without damage — and in fact makes them better.

One candidate for a semiconductor insulator is spin-on organisilicate glass, a porous glassy material applied as a thin fluid film; when heated it turns into a thin glass film laced with nanopores to enhance electrical insulation. Whereas conventional photoresist etching processes can compromise the delicate material, NIL could pattern SOG layers with wiring trenches, and eliminate litho steps by patterning the film accurately without destroying the lacework, NIST claims.

Last fall NIST published a paper in Advanced Materials addressing the patterning issue, showing that NIL used on functional SOG material could transfer patterns with <100nm detail and minimal distortion due to processing.

Now, in another paper being published in Advanced Materials, NIST scientists claim they extend the effect of the embossing process on the nanopore structure in the glass. Using a combination of techniques to measure nanopore distribution in the insulator, they found that the NIL embossing process actually increases the population of small pores, improving performance, reducing population of larger pores, and creating a thin, dense protective skin across the material’s surface.

Electron micrograph shows a cross-section of a typical SOG microcircuit feature (color added for clarity). Nanoporous regions in the interior are lighter. The process forms a dense, stronger skin ~2nm thick on the outside. (Source: NIST)

Together, NIST says, these two papers suggest that NIL “can produce superior nanoporous insulator layers in advanced semiconductor devices with significantly fewer


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