Mechanism of Impurity Content in Degradation and Damage Characteristics of Calcium Fluoride Crystals by X-Ray and Deep-Ultraviolet Laser Irradiation

Mechanism of Impurity Content in Degradation and Damage Characteristics of Calcium Fluoride Crystals by X-Ray and Deep-Ultraviolet Laser Irradiation

Calcium fluoride (CaF<sub>2</sub>) crystals are widely utilized in deep-ultraviolet (DUV) lithography due to their excellent optical properties. The laser-induced degradation and damage of CaF<sub>2</sub> crystals is a critical concern that restricts its extended application....

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Main Authors: Ping Han, Dapeng Jiang, Huamin Kou, Rongrong Liu, Qinghui Wu, Zhonghan Zhang, Zhen Zhang, Chong Shan, Chongyun Shao, Yafei Lian, Yuanan Zhao, Xing Peng, Liangbi Su
Format: Article
Language:English
Published: MDPI AG 2025-06-01
Series:Photonics
Subjects:
calcium fluoride crystals
deep-ultraviolet lithography
laser-induced degradation and damage
laser-induced damage thresholds
Online Access:https://www.mdpi.com/2304-6732/12/6/579
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Summary:Calcium fluoride (CaF<sub>2</sub>) crystals are widely utilized in deep-ultraviolet (DUV) lithography due to their excellent optical properties. The laser-induced degradation and damage of CaF<sub>2</sub> crystals is a critical concern that restricts its extended application. Impurities of CaF<sub>2</sub> crystal are considered a key factor affecting its laser resistance. Establishing the quantitative relationship and mechanism of impurity content impacting the degradation and damage characteristics of CaF<sub>2</sub> crystal is essential. This study investigated the characteristics of different impurity contents affecting the degradation and laser-induced damage thresholds (LIDTs) of CaF<sub>2</sub> crystals under X-ray and 193 nm pulsed laser irradiations, and quantitatively analyzed the degradation process and mechanism. Our findings demonstrate that impurities at ppm levels significantly diminish the transmittance of CaF<sub>2</sub> crystals across various wavelengths following X-ray irradiation. In contrast, these impurities have a negligible effect on the LIDT test results, suggesting distinct damage mechanisms between X-ray and laser irradiation. This study provides valuable insights for optimizing the CaF<sub>2</sub> crystal fabrication process and enhancing irradiation resistance.
ISSN:2304-6732

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