Journal of Vacuum Science & Technology B, Vol.27, No.6, 2558-2562, 2009
Amino-propyl-triethoxy-silane on aluminum fiducial grids for spatial-phase-locked electron-beam lithography
A new fiducial grid suitable for low-energy (1-5 keV) spatial-phase locked electron-beam lithography (SPLEBL) has been developed based on an aluminum layer with an organosilane grid pattern. The grids (400 nm period) were made of two to three layers of 3-amino-propyl-triethoxy-silane (APTES) that was microcontact printed onto Al coated polymethyl methacrylate (PMMA). Signal-to-noise ratios (SNRs) were measured at beam energies ranging from 1 to 5 keV at a dose of 20 mu C/cm(2) and compared to the SNRs of octadecanethiol (ODT) based fiducial grids on Au, Ag, and Cu. Although fiducial grids made of ODT on Au provided excellent SNR, Au is not suitable because of poor penetration and strong scattering of the primary electrons. ODT based grids on lower atomic number metal such as Ag or Cu yielded inadequate SNRs. In contrast, APTES-based grids on Al provide SNRs approaching ODT on Au with greatly reduced electron scattering. The authors successfully developed a grid removal process that allows patterns to be resolved in the underlying PMMA. These results represent a key step in the development of low-energy SPLEBL.