Young's Modulus Measurement of Submicron-thick Aluminum Films Using Fan-shaped Silicon Resonators

In this paper, we describe a way of finding the optimum resonator geometry required to determine a reasonably accurate Young's modulus of submicron-thick Al films. The films with thicknesses ranging from 15 to 380 nm are deposited onto the back of specially designed fanshaped resonators by vacuum evaporation. Young's modulus is calculated from the difference in resonant frequencies obtained before and after the deposition. By using resonators with the support beam length larger than 75 m and cross-sectional aspect ratio larger than 1.0, the measured Young's moduli of the Al films are close to the bulk value. When the films were thicker than 50 nm, the moduli show no film thickness effect (57.5 5.8 GPa on average). Young's moduli measured by resonance testing are compared with those measured by nanoindentation testing. The reliability of the measured Young's moduli is discussed in light of resonant frequency and film thickness measurement cancellations of significant digits.