Influence of surface roughness of Bragg reflectors on resonance characteristics of solidly-mounted resonators.
The solidly mounted resonator (SMR) is fabricated using planar processes from a piezoelectric layer sandwiched between two electrodes upon Bragg reflectors, which then are attached to a substrate. To transform the effective acoustic impedance of the substrate to a near zero value, the Bragg reflectors are composed of alternating high and low acoustic impedance layers of quarter-wavelength thickness. This paper presents the influence of Bragg reflector surface roughness on the resonance characteristics of an SMR. Originally, an A1N/A1 multilayer is used as the Bragg reflector. The poor surface roughness of this Bragg reflector results in a poor SMR frequency response. To improve the surface roughness of Bragg reflectors, a molybdenum (Mo)/titanium (Ti) multilayer with a similar coefficient of thermal expansion is adopted. By controlling deposition parameters, the surface roughness of the Bragg reflector is improved, and better resonance characteristics of SMR are obtained.
Chung
Chung-Jen
CJ
Department of Electrical Engineering, National Sun Yat-Sen University, Kaohsiung, Taiwan, R.O.C.
Chen
Ying-Chung
YC
Cheng
Chien-Chuan
CC
Wei
Ching-Liang
CL
Kao
Kuo-Sheng
KS
D000162:Acoustics / Q000295:instrumentation*; D003198:Computer Simulation; D017097:Electric Impedance; D004867:Equipment Design; D019544:Equipment Failure Analysis; D008422:Materials Testing; D008962:Models, Theoretical; D012031:Refractometry / Q000295:instrumentation*; D013499:Surface Properties; D014159:Transducers