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

Abstract

Chemical amplification positive resists using tetrahydropyranylprotected polyvinylphenol (THP-M) were investigated for electron-beam lithography. To enhance the resist performance, we used a new novolak resin and trimethylsulfonium triflate (IvIES) as an acid generator. The novolak resin has a large dissolution inhibition effect, and MES shows the dissolution promotion effect. Therefore, the resist composed of these systems showed the high performance. It resolved 0.3 j m hole pattern with the aquous base development using an electron-beam lithography system with a dose of 4.7 p C/cnf. 1.IntroductionElectron-beam direct writing technology is the most promising candidate among microfabrication techniques after optical lithography. The technology of electron-beam writing has been widely used for photomask fabrication. However, there are several problems to apply this technology to future lithography. A serious problem with electron-beam litography is low throughput. Recently, cell projection has been proposed to improve the throughput [1][2]. The concept of this technology is based on exposing an array of memory cell in one shot by electron projection lithography. However, a conventional resist with low sensitivity is not to its advantage.Chemical amplification is a well-known technique giving the high sensitivity required for various microlithography resists [3]. 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. Tetrahydropyranyl-proteced polyvinylphenol (THP-M) was selected as the most effective dissolution inhibitor. As the tetrahydropyranyl (THP) group is an acid labile group to protect the hydroxyl group [12][13], it was shown that a radiation-induced acid catalyzes the deprotection of the THP group on the polymer. We have already reported on a conventional novolak-resin based chemical amplification positive resist using tri(metanesulfonyloxy)benzene (MeSB) as an acid generator for electronbeam lithography [10]. The performance of this resist system is sufficient for photomask fabrication. However, it is low for single-layer resist process, because the decomposition degree of MeSB at a practical dose is only a few per cent and a dissolution inhibition effect of novolak-resin is small. In this paper, we report on the chemical amplification positive resist using the novolak-resin of which dissolution inhibition effect is large and trimethylsulfonium triflate (MES) as a new acid generator. Experimental MaterialThe novolak r...

Structural Design of Resin Matrix and Acid-labile Dissolution Inhibitor of Chemical Amplification Positive Electron-beam Resist for Gigabit Lithography.

“…To enhance the dissolution rate ratio, we tried to minimize the content of the polymeric dissolution inhibitor to decrease the side reactions. In previous papers, we reported on the design of a resin matrix which shows a large dissolution inhibition capability of the polymeric inhibitor [4,5]. In that study, we found that the m/p-cresol novolak synthesized under p-cresol rich feed ratio condition has good potential as the resin matrix.…”