Evaluation of Next Generation Fluids for ArF Immersion Lithography Beyond Water

概要

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Optical immersion lithography using fluids with refractive indices greater than that of water (1.44) can enable numerical apertures of 1.55 or above for printing sub-45 nm lines. We continue to work on delivering second generation high index immersion fluid technology to extend immersion lithography. Several fluids have been optimized to meet the required specifications of refractive index (n ≥ 1.64) and absorbance (< 0.10 / cm) at 193 nm. Here, we report on recent processing studies on two of our leading fluid candidates, designated IF132 and IF169. We are developing methods to ensure reproducible, low-absorbance fluid with low particle counts. We have also studied fluid changes on exposure to 193nm laser irradiation, and have quantified both photobleaching and photodarkening processes as a function of a number of fluid and process parameters. Through the development of a Standard Stepper Tool model, we are able to correlate our test system results to those expected in a commercial exposure system. Finally, studies of fluid-resist interactions - including PAG leaching measurements, resist thickness changes, and resist surface residues and defects - are providing valuable information on fluid compatibility with 193nm photoresists, and the effects of fluid purity on such interactions.
The Society of Photopolymer Science and Technology (SPST)の論文