Design and Chemistry of Advanced Deep-UV Photoresists: The Role of the Photoacid Generator

Abstract

Advanced deep-UV photoresists are studied from the standpoint of understanding the chemical design principles behind resist lithographic performance. The role of the photoacid generator in defining lithographic performance of deep-UV photoresists is investigated for high and low activation energy resists respectively. State of the art high and low temperature processed resists are studied with emphasis on the structure of the acid sensitive protecting group. The acid sensitive protecting group is considered in terms of the activation energy for resist deprotection. The lithographic behavior of the photoacid generator in each resist platform is probed in terms of the structure of the photogenerated acid and the light sensitive chromphore. Firstly, the lithographic impact of the photogenerated acid is investigated in terms of acid strength and acid size in resists optimized for high and low temperature processing, respectively. Dissolution kinetics, contrast curve data and absorbance data are presented for a series of high and low activation energy resists in which the structure of the photogenerated acid is systematically varied. The results of these studies are discussed in terms of the photogenerated acid, emphasizing the impact of acid strength and size on lithographic performance and resist dissolution rate kinetics for each resist platform. Secondly, the structural influence of the light sensitive PAG chromophore is investigated by comparing the lighographic performance and acid generating efficiency of iodonium and sulfonium salt PAGs.