Ryotaro Hanawa

Investigation of cyclopolymerization for ArF positive photoresist

Cyclopolymerization methodology is unique because it uses a standard free radical polymerization that is free from the use of metal catalyzed chemistry while it still can provide the main chain cyclic structure. The feasibility and applicability have been examined previously, from which some of the potential opportunities have been revealed. Our initial research direction was aimed at developing robust etching resistant acrylic resins through cyclopolymerization. During the course of our investigation it came to our attention that there might be more than one benefit we could get from this approach and here in reported is our recent progress in the study. A series of diacrylic monomers and their cyclic polymers have been prepared and evaluated for ArF optical lithography applications. The reaction of acrylic esters that have essential functional groups for lithographic performances such as an acid-cleavable bulky adamantyl group and a polar lactone group with formaldehyde in the presence of diazabicyclo-(2,2,2)octane has been shown to provide access to an ether linked symmetric or asymmetric diacrylic monomer depending on the starting materials with a reasonable yield after an adequate purification procedure. While the main research focus of cyclopolymerization of diacrylic monomers has been an improvement of dry etching resistance, an equal interest was placed on enhancing homogeneity in the polymerization reaction medium.

Effect of fluorinated monomer unit introduction to KrF resin system in F2 lithography

We reported the novel copolymer system containing fluorine atom with hydroxystyrene (HST) and 3-(perfluoro-3- methylbutyl)-2-hydroxypropyl methacrylate (MBHPMA). Using the copolymer, melamine crosslinker and PAG, negative resist was formulated. Transmittance of the resist film was 35% at 0.1micrometers thickness. High contrast negative pattern was obtained by F2 excimer laser exposure. Dry-etching resistance of the resist was comparative to novolak type i- line resist.

Resist composition effects on ultimate resolution of negative-tone chemically amplified resists

Chemical Amplification Resists (CAR) are now widely used in optical lithography since the introduction of the deep UV era. One advantage of the CARs is also their full compatibility with electron beam writing. This paper is focused on the development work of a negative tone resist. The influence of resist compounds such as polymer matrix composition and PAG size on diffusion and ultimate resolution is detailed. Finally the pattern transfer capabilities of a 30 nm isolated line into a polysilicon layer is presented.

Design of PACs for high-performance photoresists (II): effect of number and orientation of DNQs and -OH of PACs on lithographic performances

PACs which have a defined number of DNQs and -OH groups were synthesized with high yield by the selective esterification method, and the relationship between number and orientation of DNQs, and lithographic performances and dissolution properties, were examined and measured by puddle development. From our present and previous examinations, it is concluded that existence of one -OH group and two DNQs, which are separated from each other on a ballast molecule, is the most preferable structure of PAC, which provides a photoresist not only a high (gamma) -value and resolution capability but also suitable sensitivity and a scum-free pattern. According to concept of polyphotolysis results are discussed quantitatively by dissolution inhibition effect and the number of DNQs of the PAC.

Design of PACs for high-performance photoresists (I): role of di-esterified PACs having hindered -OH groups

Steric hindrance on a ballast molecule causes selective esterification of -OH groups and provides novel di-esterified PACs having -OH group(s) with high selectivity. These novel PACs give photoresists higher sensitivities, (gamma) -values and resolutions, than those of fully esterified PACs. Also, these novel PACs provide scum-free patterns. Comparison of dissolution properties of a novel di-esterified PAC having a sterically hindered -OH with those of a di-esterified PAC suggests that the presence of -OH enhances dissolution rates, but it does not change the slope of logR-logE plots. DRMs agitated development reduces a large (gamma) -value of a novel PAC observed in puddle development. On the other hand, (gamma) -values of fully esterified PACs were not affected by the change of development methods. This observation suggests significance of (gamma) - value evaluation by puddle development for the investigation of high performance PACs.

Negative-tone CAR resists for e-beam lithography: modification of chemical composition for R&D application (high resolution) or production application (high sensitivity)

In this study, it is investigated how chemical modifications of a given resist platform can induce improvements in e-beam lithographic performances. Molecular weight (Mw) as well as photo-acid generator (PAG) modifications will act as fine tuners for Sumitomo NEB-33 negative resist to match specific applications: preparation of advanced CMOS R&D architecture (highly resolving resists needed) and fast patterning for production environment (highly sensitive resists needed).

Tandem type resin for chemically amplified KrF positive resist

A mixture of high Mw fractionated novolac resin and 2EAdMA (2-ethyl-2-adamantyle methacrylate)/HST (hydroxy styrene) copolymer brought about high resolution almost comparative to simple 2EAdMA/HST copolymer. Dry etching resistance was higher than 2EAdMA/HST copolymer. A mixture of unfractionated novolac resin and 2EAdMA/HST copolymer showed low resolution. Discrimination curve was measured by DRM on each case. Dissolution contrast of fractionated mixture was almost same as unfractionated one. Dissolution characteristics cannot tell the difference of resolution between fractionated and unfractionated novolac mixture.