Development of positive electron-beam resist for 50 kV electron-beam direct-writing lithography

Abstract

A positive chemical amplification resist system has been developed for 50 kV electron-beam direct-writing lithography. This resist consists of a meta-cresol/para-cresol novolak resin, tetrahydropyranyl-protected polyvinylphenol (THP-M) as a polymeric dissolution inhibitor, and tri(methanesulfonyloxy)benzene (MeSB) as an acid generator. Radiation-induced hydrolysis of MeSB in the novolak resin matrix was confirmed to yield methanesulfonic acid and phenol derivatives by using gel-permeation and high-performance liquid chromatography. The catalytic chain length of THP-M deprotection was estimated to be approximately 300 in the matrix. It was found that the compatibility of a polymeric dissolution inhibitor with a novolak matrix relates to their polarity characteristics, and that the increase of para-cresol ratio in the novolak matrix can enhance the compatibility with THP-M and dissolution-inhibition capability of the composition. The optimized composition and process of the resist system achieved high aspect ratio patterns (0.3-μm contact holes/1.6-μm thickness) with high sensitivity (3.5 μC/cm2 at 50 kV).

Radiation Chemistry in Chemically Amplified Resists

“…[45][46][47][48][49][50][51] The decomposition through electron attachment is called dissociative electron attachment. The ratio of acid yield generated through direct excitation to that generated through dissociative electron attachment depends on the acid generator concentration.…”

“…As an alternative path, decomposition through electron transfer from the excited states of polymers has been suggested. 49,52,53) However, the acid generation processes involving electron transfer to acid generators are complicated because the deprotonation of the polymer is associated with the acid generation process. 54) The details of this reaction path are still unknown.…”

“…The photochemistry of acid generators such as onium salts, 45,46) halogen compounds, 47) nitrobenzyl esters, 48) alkylsulfonates, 49) imidosulfonates, 50) and disulfones 51) has been investigated. In particular, the decomposition mechanisms of acid generators through their excited states, which are excited directly or through energy transfer from the excited states of polymers, have been well studied.…”

Fundamental Studies of Acid-Breakable Resins for Chemical-Amplification Positive Resist Matrices.

“…We have developed novolak-resin-based chemical-amplification (CA) resists for electronbeam direct-writing lithography [1,2]. These resists consist of a novolak resin, a dissolution inhibitor with an acid-labile protection group, and an acid generator (AG).…”

Development of positive electron-beam chemical amplification resists using tetrahydropyranyl-protected polyvinylphenol.

“…In recent papers,chemical amplification resist systems using aqueous-base soluble resins, novolak, and/or phenolic resins as the matrix have been reported [4][5][6][7][8]. These resins are advantageous for the electron-beam resist matrix due to their good etching resistance and non-swelling developability [9].In a previous paper, we proposed a novolak resin-based positive chemical amplification resist utilizing a solubility reversal mechanism [10][11]. The resist system consists of a novolak matrix resin, an acid generator, and a polymeric dissolution inhibitor which can be converted to a dissolution promoter with an acid-catalyzed reaction.…”