The Liquid Sensor Using Thin Film Bulk Acoustic Resonator with C-Axis Tilted AlN Films

Ying-Chung Chen,Kuo-Sheng Kao,Chien-Chuan Cheng,Wei-Tsai Chang,Chun-Hung Yang

doi:10.1155/2013/245095

Abstract

Dual-mode thin film bulk acoustic resonator (TFBAR) devices are fabricated with c-axis tilted AlN films. To fabricate dual-mode TFBAR devices, the off-axis RF magnetron sputtering method for the growth of tilted piezoelectric AlN thin films is adopted. In this report, the AlN thin films are deposited with tilting angles of 15° and 23°. The frequency response of the TFBAR device with 23° tilted AlN thin film is measured to reveal its ability to provide dual-mode resonance. The sensitivities of the longitudinal and shear modes to mass loading are calculated to be 2295 Hz cm2/ng and 1363 Hz cm2/ng with the mechanical quality factors of 480 and 287, respectively. The sensitivities of the longitudinal and shear modes are calculated to be 0 and 15 Hz cm2/μg for liquid loading.

Highlights

Surface and bulk acoustic resonator devices are attracting increasing attention owning to their use in various novel sensors, including UV sensors, mass sensors, biosensors, and others [1,2,3]
Low-stress silicon nitride was deposited by low-pressure chemical vapor deposition (LPCVD) as the etching mask for the integrated FBAR device
This paper presents a dual-mode thin film bulk acoustic resonator (TFBAR) device that is based on c-axis-tilted AlN thin films

Summary

Introduction

Surface and bulk acoustic resonator devices are attracting increasing attention owning to their use in various novel sensors, including UV sensors, mass sensors, biosensors, and others [1,2,3]. Surface acoustic resonators have been developed and examined for potential sensor applications because they are cheap and small. Surface acoustic resonators suffer from high insertion loss and poor power handling. Thin film bulk acoustic resonator (TFBAR) devices have been studied globally; they have a low insertion loss, a high power handling capability, small size, and high sensitivity [4,5,6]. This work develops a dual-mode TFBAR device based on an adapted via-isolated resonator with piezoelectric thin film whose c-axis is tilted. The back-etched cavity is used as the sensing area

Methods

Results

Conclusion