K. Hashimoto et al., NEW CHEMICALLY AMPLIFIED POSITIVE RESIST FOR ELECTRON-BEAM LITHOGRAPHY, Journal of vacuum science & technology. B, Microelectronics and nanometer structures processing, measurement and phenomena, 12(1), 1994, pp. 37-43
A novel chemically amplified positive resist with high sensitivity for
electron beam (EB) direct-writing lithography has been developed for
deep submicron pattern fabrication. This positive EB resist consists o
f a tert-butoxycarbonyl group-protected poly (p-vinylphenol) type matr
ix polymer installing cyano group and a metal-free photoacid generator
(PAG). The matrix polymer is insoluble in aqueous alkaline solutions.
The acid-catalyzed deprotection of matrix polymer results in poly (p-
vinylphenol), which can be easily dissolved in an aqueous alkaline sol
ution. Three types of monomers, which can generate an acid by EB irrad
iation, are investigated as PAG in this resist system. Resist pattern
profile is dependent on PAG characteristics, and the profile could be
tapered in spite of the high contrast. It is found that ketosulfone-ty
pe PAG is one of the most effective catalysts for this resist system.
High resist sensitivity below 1.5 muC/cm2 at 20 keV is obtained after
postexposure bake at 90-degrees-C. Reverse tapered profile in a 0.5 mu
m thick resist can be achieved in a 0.2 mum line and space resist patt
ern by using a conventional alkaline developer. This new positive EB r
esist can be used to delineate 0.35 mum device patterns in a trilayer
resist process. Furthermore, 0.2 and 0.3 mum line and space patterns i
n 0.5 and 1.0 mum film thickness, respectively, can also be fabricated
below 2.0 muC/cm2 at 50 keV.