Hiroaki Fujishima

Standard developer available ArF resist and performance

Alicyclic groups are preferable resin components of ArF resists due to better dry-etching resistance and higher transparency at 193 nm. On the other hand, Alicyclic groups bring poor adhesion of ArF resists during wet development, because of their higher hydrophobic nature. To avoid the peeling problem diluted developer has been suggested to use. However, the compatibility with existing standard developer of i-line and KrF resists is necessary for the mass production. In this paper we compared two kinds of resists for the standard developer (TMAH 2.38%) application. The former has AdCEE unit and norbornene derivative/maleic anhydride alternating copolymer, together with relatively weak organic acid generating PAG. The latter having 2MAdMA/GBLMA copolymer and onium salt PAG shows better lithographic performance.

Positive ArF resist with 2EAdMA/GBLMA resin system

We compared 2MAdMA(2-Metyl-2- Adamantylmethacrylate)/GBLMA((gamma) -butyrolactone methacrylate) resin system and 2EAdMA(2-Etyl-2- Adamantylmethacrylate)/GBLMA resin system. 2EAdMA/GBLMA resin system showed higher sensitivity, dissolution contrast and better adhesion to silicon substrate than 2MAdMA/GBLMA resin system. These results shows that 2EAdMA/GBLMA resin system is suitable for practical ArF positive resist.

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.

Comparison of acrylate and methacrylate resin system in ArF lithography

Using 2MAdMA(2-Metyl-2-Adamantylmethacrylate), 2MAdAA(2-Metyl- 2-Adamantylacrylate), GBLMA((gamma) -butyrolactone methacrylate), GBLAA((gamma) -butyrolactone acrylate) monomers, 4 types of copolymers, 2MAdMA/GBLMA, 2MAdMA/GBLAA, 2MAdAA/GBLMA, 2MAdAA/GBLAA resins were prepared. The same PAG formulation was applied to these resins to make ArF resist samples. Resolution capability, dry-etching resistance were evaluated. From the result, it can be concluded that 2MAdAA/GBLMA resin system has the best balance in dry etching resistance, resolution and sensitivity.