Sensitivity Improvements for Picosecond Ultrasonic Thickness Measurements in Gold and Tungsten Nanoscale Films
作者机构：Key Laboratory of Opto-Electronic Information Science and Technology of Ministry of EducationSchool of Precision Instruments and Opto-Electronics EngineeringTianjin UniversityTianjin 300072China State Key Laboratory of Precision Measuring Technology and InstrumentsTianjin UniversityTianjin 300072China
出 版 物：《Nanomanufacturing and Metrology》 (纳米制造与计量（英文）)
年 卷 期：2024年第7卷第2期
页 面：1-12页
核心收录：
学科分类：07[理学] 070205[理学-凝聚态物理] 08[工学] 080501[工学-材料物理与化学] 0805[工学-材料科学与工程（可授工学、理学学位）] 0702[理学-物理学]
基 金：supported by the National Natural Science Foundation of China(Grant No.52075383) the National Key Research and Development Program of China(Grant Nos.2022Y FF0708300,2022YFF0706002)
主 题：Picosecond ultrasonics Thickness measurement Optical pump-probe Beam distortion technique
摘 要：Picosecond ultrasonics,as a nondestructive and noncontact method,can be employed for nanoscale metallic film thickness *** sensitivity of the system,which determines the measurement precision and practicability of this technique,is often limited by the weak intensity of the ultrasonic *** solve this problem,we investigate the distinct mechanisms involved in picosecond ultrasonic thickness measurement for two types of metals,namely tungsten(W)and gold(Au).For thickness measurement in W films,theory and simulation show that optimizing the pump and probe laser wavelengths,which determine the intensity and shape of the ultrasonic signal,is critical to improving measurement sensitivity,while for Au film measurements,where acoustic-induced beam distortion is dominant,the signal intensity can be optimized by selecting an appropriate aperture size and sample *** above approaches are validated in experiments.A dual-wavelength pump-probe system is constructed based on a passively mode-locked ytterbium-doped fiber *** smoothing method and multipeak Gaussian fitting are employed for the extraction of ultrasonic *** measurement precision is achieved in a series of W and Au films with thicknesses of 43-750 *** work can be applied to various high-precision,noncontact measurements of metal film thickness in the semiconductor industry.
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