Numerical Analysis of Bragg Reflector Type Film Bulk Acoustic Wave Resonator

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J. Korean Ceram. Soc. > Volume 38(11); 2001 > Article

Journal of the Korean Ceramic Society 2001;38(11): 980.

수치적 계산을 이용한 Bragg Reflector형 탄성파 공진기의 특성 분석

김주형, 이시형¹, 안진호², 주병권, 이전국¹

한국과학기술연구원 정보재료 소자연구센터
¹한국과학기술연구원 박막기술연구센터
²한양대학교 재료공학과

Numerical Analysis of Bragg Reflector Type Film Bulk Acoustic Wave Resonator

ABSTRACT

Bragg reflector type FBAR was fabricated on the Si(100) substrate. We measured a frequency response of the resonator at 5.2 GHz and analyzed it by numerical calculation considering actual acoustic losses of each layer in the structure. We fabricated nine layer Bragg reflector of W-SiO$_2$pairs using r.f. sputtering method and fabricated AlN piezoelectric and Al electrodes using pulsed dc sputtering. The return loss(S$_{11}$) of the fabricated Bragg reflector type FBAR was 12 dB at 5.38 GHz and the series resonance frequency(f$_{s}$) was 5.376 GHz and the parallel resonance frequency(f$_{p}$) was 5.3865 GHz. Effective electro-mechanical coupling constant (K$_{eff{^2}}$) and Quality factors(Q$_{s}$), the Figures of Merit of the resonator, were about 0.48% and 411, respectively. We extracted acoustic parameters of AlN piezoelectric and reflection coefficient of the Bragg reflector by numerical calculation. We could know that material acoustic impedance and wave velocity of AlN piezoelectric decreased for intrinsic value and the electromechanical coupling constant(K$_2$) value was very low owing to the poor quality of the AlN piezoelectric. Reflection coefficient of Bragg reflector was 0.99966 and reflection band was very wide from 2.5 to 9.5 GHz.

Key words: Bragg reflector, FBAR, AlN, Pulsed dc