Talbot effect immersion lithography by self-imaging of very fine grating patterns

• Published in: Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures Vol. 30; no. 6
• Main Author: Sato, Takashi
• Format: Journal Article
• Language: English
• Published: 01.11.2012
• Subjects: ArF; quartz; Cr
• ISSN: 2166-2746; 1520-8567; 2166-2754
• DOI: 10.1116/1.4767440

Talbot effect immersion lithography was investigated to improve resolution based on simulation results. The resolution limit of typical projection optics is determined by the wavelength λ of the light source and the numerical aperture. Alternatively, the Talbot effect forms self-images with no projection optics. For our simulations, the authors proposed using a mask with a Cr pattern illuminated by 193 nm ArF laser. The authors also assumed that the gap under the mask was filled with high-index immersion fluid of n = 1.64. The finite difference time domain (FDTD) optical simulation is shown for various pitches from 110 to 200 nm. So far, the distance of the self-imaging period has been estimated by second-order approximation, but the estimated result is found to differ significantly from the FDTD result. The periodic distance from low-order diffractive rays should be estimated by a higher-order approximation or an analytical method. Using Talbot effect immersion lithography, the one-dimensional line-and-space pattern of 60 nm pitch and the two-dimensional contact hole of 70 nm pitch can be transferred by a 193 nm light source.