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. Interestingly, this dramatic 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 the 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. The major resolution improvement in this system indicates that nanocomposite systems are promising candidates for sub-100 nm resolution e-beam lithography. A mechanism, explaining the electron-nanocomposite interactions at the origin of line broadening reduction, is proposed and tentatively backed by preliminary Monte Carlo simulations.
We acknowledge the help of L. Merhari, CERAMEC R&D Limoges France and W.H. Bruenger, Fraunhofer Inst. For Silicon Technology (IsiT), Itzehoe, Germany
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