Effect of structural relaxation at bellow crystallization temperature on internal stress of Ni–Nb–Zr thin film amorphous alloys diaphragm for micro electromechanical systems sensors

Abstract

In this paper, the effect of structural relaxation at temperatures below crystallization on internal stress of Ni–Nb–Zr thin film amorphous alloy (including thin film metallic glass: TFMG) diaphragms was investigated. We fabiricated the Ni–Nb–Zr diaphragm samples with four compositions. Before fabrication of diaphragm structure by etching, Ni–Nb–Zr thin films on Si substrate were annealed at a temperature below crystallization (473, 523, and 573 K) for structural relaxation. By performing bulge tests on annealed Ni–Nb–Zr diaphragms, we were able to determine their mechanical properties. As the result, Young’s modulus of all samples increased slightly with increasing annealing temperature because of the decrease of the free volumes during structural relaxation. Based on the results of internal stress, structural relaxation of all samples occurred below 473 K. Moreover, the effects of annealing temperature on internal stress differed by compositions. They were thought to be caused by the rate of structural relaxation.