Abstract
It is challenging to implement extreme ultraviolet (EUV) lithography in mass production because of strict requirement for EUV resist materials. Under this circumstances, it is important in EUV resist design to clarify the dissolution behavior of the resist film in the alkaline developer. In particular, the dissolution in exposed areas of resist films is one of the most critical processes. However, the details of the dissolution process of EUV resists have not yet been clarified. In this study, the dissolution of poly(4-hydroxystyrene) (PHS) polymer, which is a model polymer of EUV chemically amplified resists, with and without additives such as acid generators and amines was studied by a quartz crystal microbalance (QCM) method. The effects of the acid generator concentration and the addition of amines on the dissolution behavior of PHS films were investigated by varying the exposure dose with the aim of obtaining a systematic understanding of the effect of each resist component on dissolution. Differences in the experimentally observed dissolution behaviors were associated with the effect of each resist component on dissolution. The decrease in the development rate caused by the addition of an acid generator suggests that the solubility in the developer depends on the concentration of the remaining acid generator and its structure. In particular, the electrostatic interaction between the acid generator and the hydroxyl groups in PHS has a strong effect on the solubility in tetramethylammonium hydroxide (TMAH) developer. It is important in EUV resist design to take into account the concentration of undecomposed acid generator.
