SELF-ASSEMBLED MONOLAYER ELECTRON-BEAM RESISTS ON GAAS AND SIO2

it was demonstrated that self-assembled monolayers of n-octadecanethiol [ODT; CH3(CH2)17SH] on GaAs and n-octadecyltrichlorosilane [OTS; CH3(CH2)17SiCl3] on SiO2 act as self-developing positive electron beam resists with electron-beam sensitivities of approximately 100-200 muC/cm2. For the OTS monolayer on a silicon native oxide, atomic force microscopy (AFM) images of the exposed layer before etching demonstrate the removal of all or part of the layer upon electron-beam exposure. Features as small as 25 nm were resolvable in a 50 nm period grating. A resist contrast curve for OTS was obtained from AFM depth measurements as a function of dose. An ammonium hydroxide water etch was used to transfer patterns into the GaAs to a depth of at least 30 nm and buffered HF was used for pattern transfer into the SiO2 to a depth of at least 50 nm.