Accurate Determination of the Low-Light-Level Absorption of DUV-Fused Silica at 193 nm with Laser Calorimetry

• Published in: Photonics Vol. 11; no. 4; p. 305
• Main Authors: Li, Fengting, Sun, Haojie, Liu, Weijing, Hong, Ruijin, Tao, Chunxian
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 01-04-2024
• Subjects: Absorption; Absorptivity; Calorimetry; Defect annealing; defects; Dependence; DUV fused silica; Energy; Fluence; Fused silica; Heat; Heat measurement; Integrated circuit fabrication; internal transmission; Irradiation; laser calorimetry; Laser radiation; Lasers; Light; Lithography; low-light-level absorption; Repetition; Silica; Silicon wafers; Thickness measurement; China
• ISSN: 2304-6732; 2304-6732
• DOI: 10.3390/photonics11040305

The low-light-level absorption coefficient of OH-contained and H2-impregnated synthetic fused silica material in 193 nm optical lithography application is determined via a laser calorimetry measurement. The fluence and repetition rate dependences of the absorptances of the deep ultraviolet (DUV)-fused silica samples with different thickness are measured. The measured dependences are fitted to a theoretical model, taking into consideration the generation and annealing of laser irradiation induced defects. The surface absorption, the low-light-level linear absorption coefficient, as well as the nonlinear absorption coefficient of the fused silica material are accurately determined via the fitting. The low-light-level linear absorption coefficients determined via the fluence dependence and the repetition rate dependence are in good agreement, demonstrating the reliability of the measured low-light-level absorption coefficient, which is the key parameter to the determination of the internal transmission of the DUV-fused silica material used in the 193 nm optical lithography.