Contact-hole layer patterning is expected to be one of the first applications for EUV lithography. Conventional absorber masks, however, are extremely inefficient for these layers, placing even more burden on the already challenging source power demands. To address this concern, a chromeless checker-board phase-shift mask for 25- nm dense contacts has been shown to provide a throughput gain of 8x based on characterization with the SHARP EUV microscope and 7x based on micro field patterning with the Berkeley MET. These promising experimental results warrant both assessment for implementation in practice and rigorous simulations for diagnosing 3D mask effects. In this paper we verify the theoretical benefits of phase-shift masks over traditional absorber masks in idealized Kirchhoff analysis, explore the sensitivity of patterning to deviations from the ideal scattered orders, model the etched multilayer using thin-film characteristic matrix analysis, and finally use rigorous 3D Finite-Time Time Domain (FTTD) simulations of etched multilayer masks to explore mitigation of 3D effects to achieve optimal mask designs for minimum-pitch line-space and contact array patterns.
Stuart Sherwin, Thomas V. Pistor, Andrew Neureuther, and Patrick Naulleau, "Rigorous 3D electromagnetic simulation of ultrahigh efficiency EUV contact-hole printing with chromeless phase shift mask," Proc. SPIE 10143, Extreme Ultraviolet (EUV) Lithography VIII, 1014317 (Presented at SPIE Advanced Lithography: March 02, 2017; Published: 24 March 2017); https://doi.org/10.1117/12.2260412.
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