Abstract
This paper discusses the principles under which high-resolution projection
photolithographic objectives are created and the requirements on the optical
materials used for them. It is shown that fluorite is one of the most promising
materials for creating objectives for photolithography at wavelengths 248 and 193nm. A discussion is given of the prospects for developing lens-based
projection objectives with high numerical aperture, the modern state of the
production technology, and also methods for certifying the main optical parameters
of photolithographic-quality fluorite. Fluorite crystals up to 300mm in diameter and 50mm thick have been fabricated and certified. The crystals grown using this
technology have high transmittance (99.92-99.96% at λ=193nm), good optical homogeneity [Δn=(1-4)×10<sup>−6</sup>], and low birefringence (δ=0.5-2.0nm/cm). The crystals have virtually no luminescence. Proposals are given for the
development of photolithographic optics.
© 2009 Optical Society of America
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