The Bragg Reflector Layer of Low Surface Roughness Based on Solidly Mounted Resonators

Wei-Che Shih,Chih-Yu Wen,Wei-Tsai Chang,Kuo-Sheng Kao,Po-Wei Ting,Chih-Ming Wang,Jui-Yang Chang,Kuo-Hwa Cheng,Ying-Chung Chen,Chien-Chuan Cheng

doi:10.12792/iciae2015.078

Abstract

In this study, the solidly mounted resonator (SMR) device is composed of a piezoelectric layer sandwiched between two electrodes on a Bragg reflector attached to a silicon substrate. To obtain appropriate SMR characteristics for the new-generation communication applications, the surface roughness of Bragg reflector has been investigated thoroughly. Manufacture parameters are adjusted in accordance with the results of atomic force microscopy (AFM) and scanning electron microscopy (SEM). The frequency response is measured using an HP8720 network analyzer and a CASCADE probe station. Afterwards, a ¼λ mode SMR is experimentally realized. The surface roughness of 6.442 nm and well return loss can be achieved for four-pair SiO 2 /Mo Bragg reflector.

Highlights

In recent year, the issue of the frequency bandwidth of wireless communication systems is being of great interest and attention
The solidly mounted resonator (SMR) device is composed of a piezoelectric layer sandwiched between two electrodes on a Bragg reflector attached to a silicon substrate
Five sputtering pressures with RF power of 100 W were used to study the phenomenon of Mo thin films

Summary

Introduction

The issue of the frequency bandwidth of wireless communication systems is being of great interest and attention. Thence, several acoustic devices were investigated for high frequency band such as nano-scaled surface acoustic wave (SAW) resonator[1], thin-film bulk acoustic resonator (TFBAR) [2, 3] and SMR. There are two kinds of TFBAR structure to avoided acoustic energy dissipation in substrate, including air gap isolated resonator and via isolated resonator [4,5,6,7,8,9,10], as shown in Fig. 1(a) and (b). The SMR device is composed of a piezoelectric layer sandwiched between two electrodes on a Bragg reflector attached to a silicon substrate. The surface roughness of the Bragg reflector layer is the key factor to avoid acoustic-energy scattering. The effect of SiO2/Mo numbers on the frequency response will be discussed

Experimental

Analysis of Mo thin films

Analysis of SiO2 thin films

Conclusions