NEW CHEMICALLY AMPLIFIED POSITIVE RESIST FOR ELECTRON-BEAM LITHOGRAPHY

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 of a tert-butoxycarbonyl group-protected poly (p-vinylphenol) type matrix 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 solution. Three types of monomers, which can generate an acid by EB irradiation, 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-type 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 mum thick resist can be achieved in a 0.2 mum line and space resist pattern by using a conventional alkaline developer. This new positive EB resist 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 in 0.5 and 1.0 mum film thickness, respectively, can also be fabricated below 2.0 muC/cm2 at 50 keV.