AlN film bulk acoustic wave (BAW) resonators operating at above 5 GHz for next generation mobile communications present some problems, such as the very thin thickness of the piezoelectric film and electrode films. These cause degradations of the power handling capability, electromechanical coupling factor, and Q value in film BAW resonators. Polarity-inverted multilayered AlN film BAW resonators can operate in high-order mode resonance. Therefore, an n-layer polarity-inverted film BAW resonator has n-times thicker piezoelectric film thickness than a standard BAW resonator with a monolayer piezoelectric film operating at same frequency. However, fabrication methods for polarity-inverted multilayered AlN films have not been established. This paper examines the effect of Si doping on AlN films on the crystal orientation, polarity direction, and electromechanical coupling factor (kt2). Furthermore, we fabricated and evaluated two- to eight-layer polarity-inverted SiAlN/AlN film high-overtone bulk acoustic wave resonators (HBARs). The polarity of the SixAl1−xN films inverted around x = 0.024–0.13. The crystal orientation and kt2 of the SixAl1-xN films were degraded with increasing Si concentration x. The eight-layer polarity-inverted SiAlN/AlN film HBAR resonated in the eighth mode. Moreover, the experimental longitudinal wave insertion loss exhibited a similar trend to the theoretical curve calculated by a Mason's equivalent circuit model considering the polarity inverted structure. The eight-layer polarity-inverted HBARs had approximately eight-times thicker piezoelectric film thickness than the monolayer AlN film HBAR. The insertion loss improved with increasing the number of polarity-inverted layers.

1.
R.
Ruby
,
P.
Bradley
,
J. D.
Larson
 III
, and
Y.
Oshmyansky
, “
PCS 1900 MHz duplexer using thin film bulk acoustic resonators (FBARs)
,”
Electron. Lett.
35
,
794
(
1999
).
2.
R.
Ruby
,
P.
Bradley
,
Y.
Oshmyansky
,
A.
Chien
, and
J. D.
Larson
 III
, “
Thin film bulk wave acoustic resonators (FBARs) for wireless applications
,” in
Proceedings of IEEE Ultrasonics Symposium
(
IEEE
,
2001
), pp.
813
821
.
3.
R.
Hou
,
D.
Hutson
,
K. J.
Kirk
, and
Y. Q.
Fu
, “
AlN thin film transducers for high temperature non-destructive testing applications
,”
J. Appl. Phys.
111
,
074510
(
2012
).
4.
J.
Yanez
,
F.
Torres
,
A.
Uranga
, and
N.
Barniol
, “
A feasibility study of AlN ultrasonic transducers fabrication using the multi-user PiezoMUMPs process for fingerprint scanning at GHz range
,” in
2019 15th Conference on Ph.D. Research in Microelectronics and Electronics (PRIME)
(
IEEE
,
2019
), pp.
293–296
.
5.
M.
Ueda
and
M.
Hara
, “
Development of an X-band filter using air-gap-type film bulk acoustic resonators
,”
Jpn. J. Appl. Phys.
47
,
4007
(
2008
).
6.
R.
Lu
and
S.
Gong
, “
RF acoustic microsystems based on suspended lithium niobate thin films: Advances and outlook
,”
J. Micromech. Microeng.
31
,
114001
(
2021
).
7.
A.
Vorobiev
and
S.
Gevorgian
, “
Intrinsically switchable thin film bulk acoustic wave resonators
,”
Appl. Phys. Lett.
104
,
222905
(
2014
).
8.
A.
Vorobiev
and
S.
Gevorgian
, “
Composite ferroelectric fbars that are switchable between the first and second harmonics: Experimental demonstration
,”
IEEE Trans. Ultrason. Ferroelectr. Freq. Control
62
,
565
(
2015
).
9.
M. Z.
Koohi
and
A.
Mortazawi
, “
Negative piezoelectric-based electric-field-actuated mode-switchable multilayer ferroelectric FBARs for selective control of harmonic resonances without degrading Keff2
,”
IEEE Trans. Ultrason. Ferroelectr. Freq. Control
67
,
1922
(
2020
).
10.
T.
Shimidzu
,
T.
Mori
, and
T.
Yanagitani
, “
Frequency-switchable polarity-inverted BAW resonators based on PZT/PTO epitaxial films using difference in coercive field
,”
Appl. Phys. Lett.
114
,
212902
(
2019
).
11.
T.
Shmidzu
and
T.
Yanagitani
, “
Freqency-switchable polarity-inverted BAW resonators based on electric-field-induced piezoelectric PMN-PT/PZT epitaxial film stacks
,”
J. Appl. Phys.
126
,
114104
(
2019
).
12.
K.
Katada
,
T.
Yanagitani
,
M.
Suzuki
, and
K.
Wasa
, “
Second harmonic mode polarization inverted resonator consisting of PbTiO3 thin film
,” in
Proceedings of IEEE Ultrasonics Symposium
(
IEEE
,
2014
), pp.
1
2
.
13.
T.
Yanagitani
,
N.
Morisato
,
S.
Takayanagi
,
M.
Matsukawa
, and
Y.
Watanabe
, “
C-axis zig-zag ZnO film ultrasonic transducers for designing longitudinal and shear wave resonant frequencies and modes
,”
IEEE Trans. Ultrason. Ferroelectr. Freq. Control
58
,
1062
(
2011
).
14.
T.
Yanagitani
and
S.
Takayanagi
, “
Polarization control of ScAlN, ZnO and PbTiO3 piezoelectric films: Application to polarization-inverted multilayer bulk acoustic wave and surface acoustic wave devices
,”
Jpn. J. Appl. Phys.
60
,
SD0803
(
2021
).
15.
M.
Suzuki
,
T.
Yanagitani
, and
H.
Odagawa
, “
Polarity-inverted ScAlN film growth by ion beam irradiation and application to overtone acoustic wave (000–1)/(0001) film resonators
,”
Appl. Phys. Lett.
104
,
172905
(
2014
).
16.
Y.
Sato
and
T.
Yanagitani
, “
Zig-zag ScAlN multilayer SMR for high power BAW filter application such as RF base station
,” in
2020 IEEE International Ultrasonics Symposium (IUS)
(
IEEE
,
2020
), pp.
1
3
.
17.
D.
Mo
,
S.
Dabas
,
S.
Rassay
, and
R.
Tabrizian
, “
Complementary-switchable dual-mode SHF scandium aluminum nitride BAW resonator
,”
IEEE Trans. Electron Devices
69
,
4624
(
2022
).
18.
J. D.
Larson
 III
,
S.
Mishin
, and
S.
Bader
, “
Characterization of reversed c-axis AlN thin films
,” in
Proceedings of IEEE Ultrasonics Symposium
(
IEEE
,
2010
), pp.
1054–1059
.
19.
P.
Wang
,
D.
Wang
,
S.
Mondal
,
Y.
Wu
,
T.
Ma
, and
Z.
Mi
, “
Interfacial modulated lattice-polarity-controlled epitaxy of III-nitride heterostructures on Si (111)
,”
ACS Appl. Mater. Interfaces
14
,
15747
(
2022
).
20.
S. A.
Anggraini
,
M.
Uehara
,
K.
Hirata
,
H.
Yamada
, and
M.
Akiyama
, “
Polarity inversion of aluminum nitride thin films by using Si and MgSi dopants
,”
Sci. Rep.
10
,
4369
(
2020
).
21.
T.
Mizuno
,
K.
Umeda
,
Y.
Aida
,
A.
Honda
,
M.
Akiyama
,
T.
Nagase
, and
M.
Kobayashi
, “
Germanium aluminum nitride thin films for piezo-MEMS devices
,” in
2017 19th International Conference on Solid-State Sensors, Actuators and Microsystems (TRANSDUCERS)
(
IEEE
,
2017
), pp.
1891
1894
.
22.
W. P.
Mason
,
Physical Acoustics
(
Academic Press
,
New York
,
1964
), vol. I, part A.
23.
Y.
Takano
,
R.
Hayakawa
,
M.
Suzuki
, and
S.
Kakio
, “
Increase of electromechanical coupling coefficient kt2 in (0001)-oriented AlN films by chromium doping
,”
Jpn. J. Appl. Phys.
60
,
SDDC08
(
2021
).
24.
J. F.
Rosenbaum
,
Bulk Acoustic Wave Theory and Devices
(
Artech House
,
Boston
,
1988
).
25.
Y.
Ohashi
,
M.
Arakawa
,
J.
Kushibiki
,
B. M.
Epelbaum
, and
A.
Winnacker
,
Appl. Phys. Express
1
,
077004
(
2008
).

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