Sub-10 nm Electron Beam Nanolithography Using Spin-Coatable TiO2 Resists

Conventional methods for electron beam patterning of TiO2 are based on sputtering and lift-off. This poses significant problems in producing high aspect ratio and stoichiometric structures, especially in the sub-100 nm size range. We describe an alternative approach of preparing spin-coatable TiO2 resists by chemically reacting titanium n-butoxide with benzoylacetone in methyl alcohol. They have an electron beam sensitivity of ∼35 mC cm-2 and are >107 times more sensitive to an electron beam than sputtered TiOx and crystalline TiO2 films. Fourier transform infrared studies suggest that exposure to an electron beam results in the gradual removal of organic material from the resist. This makes the exposed resist insoluble in organic solvents such as acetone, thereby providing high-resolution negative patterns as small as 8 nm wide. Such negative patterns can be written with a pitch as close as 30 nm.