Mj. Lercel et al., SELF-ASSEMBLED MONOLAYER ELECTRON-BEAM RESISTS ON GAAS AND SIO2, Journal of vacuum science & technology. B, Microelectronics and nanometer structures processing, measurement and phenomena, 11(6), 1993, pp. 2823-2828
it was demonstrated that self-assembled monolayers of n-octadecanethio
l [ODT; CH3(CH2)17SH] on GaAs and n-octadecyltrichlorosilane [OTS; CH3
(CH2)17SiCl3] on SiO2 act as self-developing positive electron beam re
sists with electron-beam sensitivities of approximately 100-200 muC/cm
2. For the OTS monolayer on a silicon native oxide, atomic force micro
scopy (AFM) images of the exposed layer before etching demonstrate the
removal of all or part of the layer upon electron-beam exposure. Feat
ures as small as 25 nm were resolvable in a 50 nm period grating. A re
sist contrast curve for OTS was obtained from AFM depth measurements a
s a function of dose. An ammonium hydroxide water etch was used to tra
nsfer 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.