Growth and Optical Properties Characterization of Deep Ultraviolet High Transmittance Quartz Crystals.

Illumination system, as one of the main parts of lithography, enables to supply high uniformity intensity distribution on the mask, controls exposure dose and creates off-axis illumination (OAI) modes, which enhance the resolution and enlarge depth of focus of lithography. Quartz crystals exhibit intrinsic birefringence in the x-direction, based on which, quartz crystal polarization device is made, and the polarization state of beam can be controlled by the device. In the lithography machine's lighting system, the resolution ratio and imaging quality can be further improved by the polarization device with off-axis illumination modes assisted. Due to the limitations of traditional quartz crystal growth process and crystal automorphism, largediameter quartz wave plate (diameter above 50 mm) which the polarization device need was always a challenge. In this study, optimized framework seed method was applied to eliminate heritable etch channel defects. Raw material ratio was optimized for further reduce the content of trace elements such as Al3+, and Na+,, etc. Temperature-rising curve was controlled to realize lattice matching on the surface of quartz seed, and weaken inhomogeneous in the epitaxial region of quartz crystal. The parameters (such as temperature, pressure, mineralizer and its concentration, opening rate of throttle flap, et al.) were systematically adjusted for quartz growth. Thereby a high transmittance quartz single crystal suitable for 193 nm wavelength was successfully synthesized and a quartz wave plate blank with maximum size of Φ160 mm was processed, which is the largest size quartz optical wave plate blank reported. Optical properties such as trace element content, internal transmittance, birefringence performance, optical uniformity and laser damage resistance were characterized. The results show that, the total content of trace elements in quartz crystal is controlled within 7 x 10-6, the internal transmittance reaches 99.80%/mm, the unevenness of birefringence difference is less than 0.029 7%, and the PV value of optical uniformity reaches 3.9 x 10-6, (effective aperture Φ140 mm). [ABSTRACT FROM AUTHOR]