Monte Carlo modeling of the photo and Auger electron production in X-ray lithography with synchrotron radiation

A Monte Carlo model has been constructed for the photo and Auger electron production in X-ray lithography with synchrotron radiation. First, the accuracy of electron simulation at low energies of 0.1-2.5 keV was checked in comparison with published experimental results of developed depths of polymethyl methacrylate (PMMA) films under electron exposure. The agreement was within about 20 percent. Next, Monte Carlo calculations of X-ray exposure on a 1.0-µm PMMA film were performed for three cases with and without Si and Au Substrates. Etching simulation of pattern profiles for an infinitely fine-line exposure was conducted combining both the solubility rate for a developer of methyl isobutyl ketone and the calculated spatial distribution of absorbed energy in the resist film. Electron orbital energies investigated were 0.7, 1.0, and 1.3 GeV in a synchrotron with a radius of 4 m. The calculated ultimate resolution was found to be about 100 nm. There was no significant difference between the ultimate resolutions at both energies. The exposure time required for the pattern fabrication was less at 1.3 GeV by a factor of 2.8 than at 1.0 GeV. With the Si substrate a favorable compensation was seen for the energy loss near the boundary due to escaped electrons, while with the Au substrate the effect was excessive, suggesting a preference of a lower energy of 1.0 GeV.