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In recent years, EUV lithography scanner systems have entered high-volume manufacturing for state-of-the-art integrated circuits, with critical dimensions down to 10 nm. This technology uses 13.5-nm EUV radiation, which is shaped and transmitted through a near-vacuum H 2 background gas. This gas is excited into a low-density H 2 plasma by the EUV radiation, as generated in pulsed mode operation by the laser-produced plasma in the EUV source. Thus, in the confinement created by the walls and mirrors within the scanner system, a reductive plasma environment is created that must be understood in detail to maximize mirror transmission over the lifetime and to minimize molecular and particle contamination in the scanner. In addition to the irradiated mirrors, reticle, and wafer, the plasma and radical load to the surrounding construction materials also must be considered. We provide an overview of the EUV-induced plasma in the scanner context. Special attention is given to the plasma parameters in a confined geometry, such as that found in the scanner area near the reticle. It is shown that plasma confinement and resulting contributions from secondary electron emission delay the formation of the plasma sheath and thereby reduce the peak ion energies to below the sputtering threshold for mirrors and construction materials. Furthermore, for a confined pulsed plasma with a pulse period shorter than the decay time of the plasma, the plasma consists of a quasi-steady-state cold background plasma and periodic transient peaks in ion energy and ion flux. In terms of modeling, this means that no assumptions can be made on the electron distribution functions and a (Monte-Carlo) particle-in-cell (PIC) model is needed. We present an extension of the PIC model approach to complex three-dimensional geometries and to multiple pulses using a hybrid PIC-diffusion approach. Also, the translation of these specific plasma parameters to off-line setups and the aspects that must be included to make a meaningful translation from off-line laboratory EUV setups to the scanner plasma are discussed. © The Authors. Published by SPIE under a Creative Commons Attribution 4.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

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Advanced optical systems for low k 1 lithography require accurate characterization of various imaging parameters to insure that OPC strategies can be maintained. Among these parameters lens aberrations and illumination profiles are the most important optical column characteristics. The phase measurement interferometer hardware (ILIAS™ : Integrated Lens Interferometer At Scanner) integrated into high-NA ArF lithographic projection tools opens novel pathways to measure and control tool critical performance parameters. In this presentation we address new extensions of this in-line tool that will allow the measurement of optical parameters of the full optical column. The primary functionality of the ILIAS™ system is to measure and analyse wavefront aberrations across the full image field with high accuracy and speed. In this paper performance data of the in-line wavefront sensor over multiple high-NA ArF lithographic systems is presented. In addition to the acquisition of wavefront aberrations in terms of Zernike polynomials, detailed measurements of high resolution wavefronts are now possible. Examples of such wavefronts and PSD analysis thereof are presented. Besides the projection lens properties, the detailed shape of the pupil distribution and transmission (apodisation) becomes critical for system optimization. The integrated ILIAS™ hardware can also be used to measure these parameters.

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