深紫外高透过石英晶体的生长和光学性能表征

摘要/Abstract

摘要： 照明系统是光刻机的重要组成部分,其主要功能是对激光光束进行扩束、整形和匀光。石英晶体x晶向具有本征双折射特点,以其原理制作的偏振装置可实现对光束偏振态的控制,配合离轴照明,能够进一步提高光刻机照明系统的分辨率和成像质量。受传统石英晶体生长工艺和晶体自范性限制,用于偏振装置的大口径石英波片(＞ϕ50 mm)一直是石英晶体研究的难题。本文利用平行定向生长水热工艺,系统调整温度、压力、矿化剂种类和浓度、节流挡板开孔率等参数,成功合成了可用于193 nm波长的高透过率石英单晶,并加工出已知报道的最大尺寸ϕ160 mm石英波片坯料。实验过程中使用改进的框架籽晶法淘汰了可遗传腐蚀隧道缺陷,通过优化原料配比进一步降低Al³⁺、Na⁺等微量元素含量,控制升温曲线实现籽晶界面晶格匹配,从而淡化籽晶外延区域均匀性差异。对单晶样品进行微量元素含量、内透过率、双折射性能和光学均匀性表征,结果表明,石英晶体微量元素总含量控制在7×10^-6以内,内透过率达到99.80%/mm,双折射率差不均匀性低于0.029 7%,ϕ140 mm有效通光口径内光学均匀性PV值达到3.9×10^-6。

关键词: 石英晶体, 照明系统, 深紫外, 波片, 偏振装置, 水热法

Abstract: 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, large-diameter 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 7×10^-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 3.9×10^-6 (effective aperture ϕ140 mm).

Key words: quartz crystal, illumination system, deep ultraviolet, waveplate, polarization device, hydrothermal method

中图分类号:

O734

张绍锋, 曹艳翠, 张璇, 李丹, 胡潇, 刘巨澜, 姜秀丽. 深紫外高透过石英晶体的生长和光学性能表征[J]. 人工晶体学报, 2023, 52(12): 2228-2234.

ZHANG Shaofeng, CAO Yancui, ZHANG Xuan, LI Dan, HU Xiao, LIU Julan, JIANG Xiuli. Growth and Optical Properties Characterization of Deep Ultraviolet High Transmittance Quartz Crystals[J]. JOURNAL OF SYNTHETIC CRYSTALS, 2023, 52(12): 2228-2234.

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