Microelectronic Engineering

Nanocomposite resist systems for next generation lithography

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A novel nanocomposite resist system was developed for sub-100 nm resolution e-beam lithography by dispersing surface-treated silica nanoparticles in a commercial ZEP520® resist. At 4.0 wt.% loading of silica nanoparticles, the system exhibited a much higher resolution than ZEP520® without sacrificing the intrinsic sensitivity and contrast of the starting polymer. The first major result is that 46 nm-wide isolated lines were obtained in the nanocomposite system (∼ 250 nm-thick layer), whereas comparatively 130 nm-wide lines were obtained in ZEP520® under the same experimental conditions. Contrary to standard e-beam resists, this important reduction of line broadening already occurred at 20 keV while higher energy e-beams (up to 100 keV) did not lead to further line broadening reduction. Moreover, it was shown that the addition of silica nanoparticles resulted in a higher resistance of the nanocomposite to plasma etching with O2 gas. Subjecting this nanocomposite resist to 75-keV Xe+ ion irradiation showed that it is also particularly suitable for ion projection lithography as a preliminary resolution of 114 nm (l/s) was obtained while the sensitivity increased by a factor of 40 compared to 30-keV electrons. Extending the nanocomposite approach to KRS-XE®, a chemically amplified resist, led to both enhanced resolution and mechanical stability for electron beam lithography. The major resolution and etch resistance improvements in both resist systems indicate that nanocomposite systems are promising candidates not only for sub-100 nm resolution e-beam lithography but also for ion projection lithography. Supported by preliminary Monte Carlo simulations a tentative mechanism highlighting the electron-nanocomposite interactions as the explanation for line broadening reduction is proposed. © 2002 Elsevier Science B.V. All rights reserved.