Mechanical characterization of thermal SiO₂micro-beams through tensile testing

Abstract

A micro-tensile testing system has been developed to measure mechanical properties of a thermal SiO 2 thin film. Through the stiffness coefficient calibration of the tensile system in situ, the deformation of the gage section is obtained using a two-serial spring model. A simple gripping method with rapid alignment is presented to improve alignment precision and repeatability of the measurement. Two kinds of specimens, including traditional ones and those with suspended spring beams, are fabricated using inductively coupled plasma (ICP) etching technology. The finished free-standing thermal SiO 2 beams are buckled because of the compressive residual stress. The residual elongation of the beams could be obtained from the original load-displacement curves of the SiO 2 beams. Thus the compressive residual stress, Young's modulus and the fracture strength of the thermal SiO 2 beams were achieved simultaneously from the tensile testing. The measured values of Young's modulus are 64.6 ± 3 GPa for traditional SiO 2 film specimens and 65.5 ± 2.8 GPa for those with suspended spring beams. The measured residual stress is 354 ± 26 MPa and the fracture strength is 426 ± 63 MPa. The measured modulus and residual stress are reasonably coherent with other reports.

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