• Journal of the Korean Ceramic Society
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• v.38 no.11
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• pp.980-986
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• 2001

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.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2002.11a
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• pp.143-147
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• 2002

In this paper, we investigated the deposition condition of Bragg reflector formation that will be expected to play an important role in future FBAR device applications. The thin films were deposited using an RF/DC magnetron sputtering technique. The material characteristics such as deposition rates, grain structures and surface roughnesses of the deposited silicon dioxide (SiO$_2$) and tungsten (W) films were investigated for various deposition conditions. As a result, it was found that the deposition condition could significantly affect the material characteristics of the deposited films and also the optimization of the deposition process is essentially important to obtain the desirable Brags reflector structure consisted of high-quality in films.

• Journal of Biosystems Engineering
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• v.34 no.4
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• pp.260-268
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• 2009

As a basic study to develop a high sensitive biosensor using film bulk acoustic resonator, the mathematical model for analyzing the resonance characteristics of bulk acoustic resonator with acoustic Bragg reflectors was investigated. The simulation results due to the number of acoustic Bragg reflectors with low and high acoustic impedance materials were compared with the experimental results for 1, 2.25 and 5 MHz of PZT based bulk acoustic resonators with various acoustic Bragg reflectors. At the fabricated bulk acoustic resonator with an odd number of acoustic Bragg reflectors, low and high acoustic impedance materials in sequence under the bottom electrode showed better resonance characteristics than even number of acoustic Bragg reflectors. The changes of resonance frequencies due to the increase of number of acoustic Bragg reflectors by simulation and experiment, respectively showed approximately similar tendency but some differences in input impedance between the experiment and simulation were found. The derived mathematical model for describing the resonance characteristics of the bulk acoustic resonator with acoustic Bragg reflector will be available for analyzing the design parameters for development of biosensor using bulk acoustic resonator.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2008.05a
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• pp.59-62
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• 2008

In this paper, we study ZnO-based a film bulk acoustic resonator (FBAR) using a multi-layered Bragg reflector. We insert chromium adhesion layers of 0.03 mm-thick to the Bragg reflector and improve the performance using thermal treatments. At operating frequency about 2.5 GHz, excellent resonance characteristics are observed in terms of good return loss and high quality factor.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.1
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• pp.371-375
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• 2005

In this paper, the resonance characteristics of ZnO-based FBAR devices are compared. Several FBAR device samples were fabricated by using three different annealing methods while one sample remained non-annealed as a reference for comparison. Resonance characteristics could be significantly improved by both Bragg reflector-annealing and/or post-annealing steps. Especially, the use of two-step annealings resulted in most desirable resonance characteristic improvement compared with the Bragg reflector-annealing or post-annealing step alone.

• Journal of information and communication convergence engineering
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• v.3 no.1
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• pp.23-27
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• 2005

In this paper, the effects of various annealing conditions on the resonance characteristics of ZnO-based FBAR devices are compared. Several FBAR device samples were fabricated by using three different annealing methods while one sample remained non-annealed as a reference for comparison. Return loss ($S_11$) could be significantly improved by both Bragg reflector-annealing and/or post-annealing. Especially, the use of the combined annealings resulted in most desirable resonance improvement compared with the Bragg reflector-annealing or post-annealing method alone.

• Journal of information and communication convergence engineering
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• v.3 no.3
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• pp.137-141
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• 2005

The paper presents some methods to improve characteristics of film bulk acoustic resonator (FBAR) devices. The FBAR devices were fabricated on Bragg reflectors. Thermal treatments were done by sintering and/or annealing processes. The measurement showed a considerable improvement of return loss $(S_{11})$ and quality factor $(Q_{s/p}).$ These thermal treatment techniques seem very promising for enhancing FBAR resonance performance.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2008.10a
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• pp.61-65
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• 2008

In this paper, we studied a ZnO-based film bulk acoustic resonator (FBAR) device fabricated on a specially designed multi-layerd Bragg reflector part. Very thin chromium adhesion layers (0,03um thick) were additionally deposited to improve the quality of the Bragg reflector and some thermal treatments were performed to improve the resonant characteristics of the device. At the operating frequency of ${\sim}2.7GHz$, excellent resonant characteristics were observed in terms of return loss and quality factor, and effective electromechanical coupling coefficient. These findings are expected to be highly promising and effective for improving the performance of the FBAR devices at high frequency.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.377-382
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• 2000

Film bulk acoustic resonator (FBAR) using AIN reactively sputtered at room temperature was fabricated. The FBAR is composed of a piezoelectric aluminium nitride thin film, top electrode of Al and bottom electrode of Au connected by a short (200${\mu}{\textrm}{m}$) transmission line on both sides and reflector layers of SiO$_2$- W Pair. The active areas of Al and Au were patterned using 150${\mu}{\textrm}{m}$ diameter shadow mask. The series resonance frequency (fs) and the parallel resonance frequency (fp) were measured at 1.976 GHz and 2.005 GHz, respectively. The minimum insertion loss and return loss were 6.1 dB and 37.19 dB, and the quality factor (Q) was 4261.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.377-378
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• 2005

In this study, $SiO_2$ thin film was deposited on variable conditions of the RF power and working pressure by RF magnetron sputtering to apply to the Bragg reflector of the SMR type FBAR device. A crystal orientation and microstructure of $SiO_2$ thin film was studied by using the XRD, AFM and SEM. The best condition was obtained through analyzing the structural characteristics of thin film. Finally, FBAR device was fabricated with applying the best condition of $SiO_2$ thin film and the resonant characteristics was investigated by network analyzer to verify application possibility as a efficient device.