A Comparative Study on the Elastic Characteristics of an Aluminum Thin-Film Using Laser Optical Measurement Techniques

Abstract

Abstract:The increase of a surface area-to-volume ratio with the reduction of material dimensions significantly alters the characteristics of materials from their macroscopic status. Therefore, efforts have been made to establish evaluation techniques for nanoscale films. While contact mechanics-based techniques are conventionally available, non-contact and nondestructive methods would be preferable in case damages left on a sample after testing are not desirable, or an in situ assessment is required. In the present study, the Young's modulus of an aluminum thin-film was evaluated using two different laser optical measurement techniques. First, microscale beam testing has been performed so that the resonant frequency change of a microfabricated cantilever beam induced by coating of a 153 nm thick aluminum layer on its top surface can be detected using a laser interferometer in order to evaluate the mechanical property through modal analysis using the finite element method. Second, picosecond ultrasonics were employed for cross-verification so that the mechanical characteristics can be evaluated through the investigation of the longitudinal bulk wave propagation behavior. Results show that the Young's moduli from both measurements agree well with each other within 3.3% error, proving that the proposed techniques are highly effective for the study of nanoscale films.

Laser-Induced Surface Acoustic Waves for Thin Film Characterization

“…The thickness of all three films was around 100 nm. Values obtained by LAW are compared with the values given by other authors [13][14][15][16][17] and in case of Al and Ti also with the results from nanoindentation. Table 1 shows that, the values of Young's modulus obtained by LAW correspond to those obtained from nanoindentation and are within the range reported in literature.…”

Elastic characterization of nanometer-thick polymeric film for astrophysics application with an experimental-numerical method

“…In Ref. 38 a useful summary of the elastic modulus of Al thin films with different thicknesses collected by several authors is reported; it is worth mentioning that, with few exceptions (33 and 102 GPa), the values were found between 55 and 81 GPa with considerable scatter. In this work, the average value of the elastic modulus for all of the samples is equal to 79 GPa, with a standard deviation of 7.7 GPa.…”

“…In Ref. 38, the elastic modulus of Al-coated films (with Al thickness>150 nm) was evaluated by means of two laser optical measurement techniques: a test approach based on a microscale beam combined with FEA and a picosecond ultrasonics wave propagation analysis. No investigations have been found in the literature, to the authors’ knowledge, on bulge mechanical characterization of PI film and Al-coated PI film with thicknesses<150 nm, which is relevant for filter applications on soft x-ray/extreme ultraviolet (EUV) astrophysics space missions.…”