Determination of Young's Modulus and Poisson's Ratio of Nanoporous Low- k Thin Film by Laser-Generated Surface Acoustic Waves
Determination of Young's Modulus and Poisson's Ratio of Nanoporous Low- k Thin Film by Laser-Generated Surface Acoustic Waves
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DOI：
10.1166/asl.2011.1531
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发表时间：
2011-03
影响因子：
--
通讯作者：
X. Shan;Xia Xiao;Ya-liang Liu
中科院分区：
文献类型：
--
作者：
X. Shan;Xia Xiao;Ya-liang Liu
A nondestructive technique for determining Young's modulus and Poisson's ratio of nanoporous thin film by laser-generated surface acoustic waves (LSAWs) is presented. The surface acoustic waves are excited through a short pulse nitrogen molecular laser source and detected by a piezoelectric transducer. An effective method to calculate the dispersion relation of frequency and phase velocity of SAWs propagating on the layered film structure is derived in detail. The inversion algorithm for extracting Young's modulus and Poisson's ratio of the film is analyzed. For isotropic thin film (thickness ≤500 nm) deposited on the Si (100) substrate, the influence of Poisson's ratio on the dispersion property of SAWs is very weak when the waves propagate along the Si [110] direction, while the influence is apparent along the Si [100] direction. Therefore, Young's modulus and Poisson's ratio can be determined by the combination of Si [110] and Si [100] direction measurements, respectively. Nanoporous SiOC:H low-k thin films are investigated by this two-direction measurement technique. Compared with the two-parameter inversion method, results indicate that the proposed approach is feasible for determining Young's modulus and Poisson's ratio of porous thin films.
