simultaneously determine of thermal expansion (a), Poisson ratio (v), and thickness (t) of thin films on a silicon wsifer. A digital phase-shifted reflection moirt (DPRM) technique was adopted to record the warpage slope of the fihdwafer composites under temperature change. These data were used to compare with the ANSYS analysis, and the genetic algorithm (GA) was employed to search for the optimal mechanical parameters of the films. In the first experiment, 1.20-um thick copper was sputtered on a 4-inch silicon wafer. The determined E, a, v, and t of this film were 95.9 Gpa, 38.7 ppm/"C, 0.16, and 1.13 um, respectively. The properties in the bulk state were found to be E=110 to 126 GF'a, a=16.6 to 17.6ppm/"C, and v=0.33 to 0.36 While the delermined film thickness was in good agreement with the measured value, the deviation in E, a and v was significant. The micro-structural difference between the bulk material and the thin film, and oxidation on the film surface were considered to be the two major causes to this deviation. The thickness of the oxidative layer was determined to be 326 nm wilh E=89.6GPa by considering the Cu-film as a two-layered stnicture. In order to verify the determined mechanical patameters of this 1.2-um Cu film, additional 2.4-um Cu film was sputtered on the CdSi wafer and the determined mechanical parameters of this additional Cu film were identical to the data obtained in the 1.2-um film, which demonstrated the validity of the developed method.
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