酸化Crバッファー層を用いた室温成膜ZnO圧電膜の開発

Abstract

Due to its piezoelectric properties, the zinc oxide (ZnO) thin film is used for Micro Electro Mechanical Systems (MEMS) sensors and actuators. In order to reduce the fabrication costs and to improve the reliability of MEMS devices, a low temperature process is desired. ZnO layer is deposited on the oxidized chrome (CrO) buffer layer that is deposited on silicon substrates. Both ZnO and CrO layers are deposited by RF magnetron sputtering at room temperature. The crystalline properties of ZnO are measured with an X-ray diffraction (XRD), a scanning electron microscopy (SEM) and an atomic force microscope (AFM). The results show that varying the O2/Ar flow ratio during the deposition of CrO layer may improve the crystalline properties of ZnO. Piezoelectrically actuated cantilevers with the ZnO thin film are fabricated and tip deflection of the cantilever is measured. The piezoelectric strain constant of ZnO thin film is calculated from the tip deflection. The results show that the piezoelectric strain constant increases and saturates with the thickness of ZnO layer. The obtained piezoelectric strain constant of ZnO thin film is 3.7 pC/N which is 74% of the bulk ZnO.