Effects of two-step deposition and thermal treatment on the frequency response characteristics of ZnO SAW devices

Abstract

Polycrystalline ZnO thin films are deposited on SiO2/Si(100) substrate using RF magnetron sputtering. The film deposition performed in this research is composed of the following two procedures; 1st-deposition for 30 min without oxygen at 100 W and 2nd-deposition with oxygen in the range O2/(Ar+O2) = 10~50 %. Deposited ZnO films reveal a strongly caxis preferred-orientation (the corresponding texture coefficient ~ 100 %) as well as a high resistivity (> 107 Ωcm). It is also observed that the crystallite size of ZnO is noticeably increased by thermalannealing. In addition, surface acoustic wave (SAW) devices are also fabricated by using a lift-off method, with the configuration of IDT/ZnO/SiO2/Si(100). Frequency response characteristics (including S21) of fabricated SAW devices are measured and device parameters including insertion losses and side-lobe rejection level estimated from frequency response are compared.