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Stress Adjustment and Characteristics Improvement in a 1.8GHz Range Film Bulk Acoustic Wave Resonator by Using Multi-layer Structure of ZnO/A12O3/SiO2

Published online by Cambridge University Press:  11 February 2011

Masaki Takeuchi ,
Hajime Yamada ,
Hideki Kawamura ,
Yoshihiko Goto ,
Tadashi Nomura ,
Hiroyuki Fujino ,
Yukio Yoshino ,
Takahiro Makino  and
Seiichi Arai
Masaki Takeuchi
Affiliation:
Murata Mfg. Co., Ltd., 2–26–10 Tenjin, Nagaoka-kyo, Kyoto, Japan
Hajime Yamada
Affiliation:
Murata Mfg. Co., Ltd., 2–26–10 Tenjin, Nagaoka-kyo, Kyoto, Japan
Hideki Kawamura
Affiliation:
Murata Mfg. Co., Ltd., 2–26–10 Tenjin, Nagaoka-kyo, Kyoto, Japan
Yoshihiko Goto
Affiliation:
Murata Mfg. Co., Ltd., 2–26–10 Tenjin, Nagaoka-kyo, Kyoto, Japan
Tadashi Nomura
Affiliation:
Murata Mfg. Co., Ltd., 2–26–10 Tenjin, Nagaoka-kyo, Kyoto, Japan
Hiroyuki Fujino
Affiliation:
Murata Mfg. Co., Ltd., 2–26–10 Tenjin, Nagaoka-kyo, Kyoto, Japan
Yukio Yoshino
Affiliation:
Murata Mfg. Co., Ltd., 2–26–10 Tenjin, Nagaoka-kyo, Kyoto, Japan
Takahiro Makino
Affiliation:
Murata Mfg. Co., Ltd., 2–26–10 Tenjin, Nagaoka-kyo, Kyoto, Japan
Seiichi Arai
Affiliation:
Murata Mfg. Co., Ltd., 2–26–10 Tenjin, Nagaoka-kyo, Kyoto, Japan
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Abstract

Stress adjustment and improvement of electrical characteristics in film bulk acoustic wave resonator (BAW) have been successfully carried out in 1.8GHz range by using a multi-layer structure of ZnO / Al2O3 / SiO2. The BAW resonator, designed on secondary harmonics at about 1.8GHz, has Al / ZnO / Al / Al2O3 / SiO2 structure. ZnO and SiO2 thin films have a negative and a positive temperature coefficient of sound velocity, respectively. So temperature coefficient of frequency (TCF) of the BAW resonator can be controlled by the thickness ratio of ZnO and SiO2 thin films. Since both ZnO and SiO2 have compressive stress, and Al2O3 has tensile one, the stress of the membrane is reduced by combining these thin films so that the membrane can avoid deformation. The BAW resonator, with thickness of ZnO / Al2O3 / SiO2=1.2 /0.45/1.25 microns, was designed by finite element method (FEM) simulation and fabricated. The value of quality factor (Q factor) and the TCF of the BAW resonator were realized over 1000 and −20 ppm/degree C, respectively. The Q of ZnO / Al2O3 / SiO2 structure was higher than that of ZnO / SiO2 one with keeping small TCF.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 741: Symposium J – Nano- and Microelectromechanical Systems (NEMS and MEMS) and Molecular Machines , 2002 , J5.9
Copyright
Copyright © Materials Research Society 2003

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References

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