Contactless measurement of Young's modulus using laser beam excitation and detection of vibration of thin-film microresonators

Young's modulus of a single-crystal thin silicon film was estimated by a noncontact method. The resonance frequencies of a microresonator fabricated using the film were measured by excitation and detection using multiple laser beams. A special configuration was adopted for the resonator to suppress the heating effect of the excite beam. Clear resonances were observed in the frequency characteristics of vibration. Young's modulus was determined from an elastic modification analysis of a spring-mass system using the resonance frequency together with the geometrical dimensions of the resonator. The deduced value of Young's modulus was 152 +/- 17 MPa, which agrees with reported values within experimental errors. The cantilever beams of the resonator had trapezoidal cross sections caused by the reactive ion etching (RIE) used in the fabrication, and their widths showed nonuniformity. The error mainly comes from the nonuniformity of the beam width along the cantilever.