ZnO-based Film Bulk Acoustic Resonator Research Articles

Streptavidin Modified ZnO Film Bulk Acoustic Resonator for Detection of Tumor Marker Mucin 1.

A ZnO-based film bulk acoustic resonator has been fabricated using a magnetron sputtering technology, which was employed as a biosensor for detection of mucin 1. The resonant frequency of the thin-film bulk acoustic resonator was located near at 1503.3 MHz. The average electromechanical coupling factor {K}_{mathrm{eff}}^2 and quality factor Q were 2.39 % and 224, respectively. Using the specific binding system of avidin-biotin, the streptavidin was self-assembled on the top gold electrode as the sensitive layer to indirectly test the MUC1 molecules. The resonant frequency of the biosensor decreases in response to the mass loading in range of 20–500 nM. The sensor modified with the streptavidin exhibits a high sensitivity of 4642.6 Hz/nM and a good selectivity.Electronic supplementary materialThe online version of this article (doi:10.1186/s11671-016-1612-5) contains supplementary material, which is available to authorized users.

ZnO-Based FBAR resonators with carbon nanotube electrodes

Film bulk acoustic resonator (FBAR) devices with carbon nanotube (CNT) electrodes directly grown on a ZnO film by thermal chemical vapor deposition have been fabricated. CNT electrodes possess a very low density and high acoustic impedance, which reduces the intrinsic mass loading effect resulting from the electrodes¿ weight and better confines the longitudinal acoustic standing waves inside the resonator, in turn providing a resonator with a higher quality factor. The influence of the CNTs on the frequency response of the FBAR devices was studied by comparing two identical sets of devices; one set comprised FBARs fabricated with chromium/ gold bilayer electrodes, and the second set comprised FBARs fabricated with CNT electrodes. It was found that the CNTs had a significant effect on attenuating traveling waves at the surface of the FBARs' membranes because of their high elastic stiffness. Three-dimensional finite element analysis of the devices fabricated was carried out, and the numerical simulations were consistent with the experimental results obtained.

Analytical and experimental study on the second harmonic mode response of a bulk acoustic wave resonator

A one-dimensional Mason model is employed to investigate the second harmonic mode response of a multilayer composite film bulk acoustic resonator (FBAR), particularly the dependence of the effective coupling coefficient (K2t, eff) on material properties and relative position in the acoustic stack. The simulation results for AlN-based FBAR with electrode layer having relatively low acoustic impedance and additional temperature compensation layer reveals that the maximum values of K2t, eff are obtained with a thickness ratio (between the non-piezoelectric layer and piezoelectric layer) that is close to its acoustic velocity ratio. The fundamental mode and second harmonic mode operation of an FBAR are compared. The maximum achievable K2t, eff is comparable (5.39% versus 5.16%) for the temperature compensated FBAR (with Mo as electrodes) operating at fundamental and second harmonic modes. However, the trimming-mass and crossover temperature sensitivities of the second harmonic mode are lower, indicating its potential advantage over the fundamental mode for high frequency applications above 2 GHz (such as filters, low phase noise temperature stable oscillator applications). Experimental results on a ZnO-based FBAR (Al/ZnO/Al/SixNy) operating around 5 GHz with various thicknesses of ZnO and SixNy show good agreement with numerical modeling.

ZnO-based film bulk acoustic resonator devices on a specially designed Bragg reflector

In this paper, we studied ZnO-based film bulk acoustic resonator (FBAR) device fabricated on a specially designed multilayered Bragg reflector part. Very thin chromium adhesion layers (0.03 μm 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 FBAR device. At the operating frequency of ∼2.7 GHz, excellent resonant characteristics were observed in terms of return loss and quality factor, and effective electromechanical coupling coefficient.

Second-order resonant ZnO-based film bulk acoustic resonator devices and thermal techniques to improve their resonant characteristics

In this article, the authors describe a novel fabrication technique of ZnO-based film bulk acoustic resonator (FBAR) devices using a new type of multilayered Bragg reflector with very thin chromium (Cr) layers additionally formed between silicon dioxide (SiO2) and tungsten (W) layers. Each Cr layer is considered to enhance the adhesion between the SiO2 and W layers. The fabricated FBAR devices are shown to operate at the frequency range of 2.7–3.0 GHz, along with good return loss as well as high Q factors. Furthermore, various thermal treatments are performed to further improve the resonant characteristics of the FBAR devices, and also their effects on the device characteristics are investigated. At the second-order resonant frequency, excellent resonant characteristics are observed in terms of high return loss and good figure of merit. This feasibility study indicates that the novel fabrication technique can be useful for future broadband mobile worldwide interoperability for microwave access applications.

ZnO-Based Film Bulk Acoustic Resonator Devices Feasible for Worldwide Interoperability for Microwave Access Applications

In this paper, we describe a novel fabrication technique of ZnO-based film bulk acoustic resonator (FBAR) devices using a new type of multilayered Bragg reflector with very thin chromium (Cr) layers additionally formed between SiO2 and W layers. Each Cr layer is considered to enhance the adhesion between the SiO2 and W layers. The fabricated FBAR devices are shown to operate at the frequency range of 2.7–3.0 GHz, along with good return loss as well as high Q-factors. Furthermore, the effects of bottom electrode thickness on the FBAR device performance are also investigated and compared. This feasibility study indicates that the novel fabrication technique can be useful for future broadband mobile worldwide interoperability for microwave access (WiMAX) applications.

Relationships between material properties of piezo-electric thin films and device characteristics of film bulk acoustic resonators

The relationships between the material properties of piezo-electric thin films (such as ZnO and AlN) and the frequency response characteristics of film bulk acoustic resonator (FBAR) devices based on those films are examined. ZnO and AlN films are deposited by RF magnetron plasma reactive sputtering. Issues in film growth are focused on electric bias application, oxygen incorporation, and two-step deposition. The XRD spectra, AFM topographies, and SEM images measured from all the deposited films present the optimal condition for both ZnO and AlN films to have excellent piezo-electric properties. For ZnO films, excessive injection of oxygen deteriorates the crystal quality and increases the surface roughness. Applying negative d.c. bias during deposition contributes to the improvement of crystal quality of ZnO films as well as the enhancement of acoustic coupling capability of ZnO-based FBAR devices. By adopting the two-step method to deposit AlN films, the films reveal the highly (002)-preferred growth nature and the RMS surface roughness values are drastically reduced, which also leads to the remarkable improvement in the acoustic coupling coefficient of AlN-FBAR devices.

Orientation fluctuation trend of Pt and ZnO layers in film bulk acoustic resonator

ZnO-based film bulk acoustic resonator (FBAR) was fabricated with many ZnO/Pt layers by magnetron sputtering. All the layers are good crystallized and highly textured. By crystallographic test, the orientation fluctuation of Pt layer increases with increasing film thickness or stack layers, whereas that of ZnO layer decreases slightly. It is consistent with ZnO grain c-axis tilting observed using transmission electron microscopy. Due to these good quality layers, the device has a high resonate frequency of 3.94 GHz.

Material and device properties of ZnO-based film bulk acoustic resonator for mass sensing applications

Zinc oxide based film bulk acoustic resonator as mass sensor was fabricated by multi-target magnetron sputtering under optimized deposition condition. Each layer of the device was well crystallized and highly textural observed by transmission electron microscopy and X-ray diffraction measurement. Through piezoelectric test, the device vibrated with significant distance. The influence of top electrode on resonant frequency and the bio-specimen of mass loading effect were investigated. Data show that the device has qualified properties as mass biosensor, with a resonant frequency of 3–4 GHz and a high sensitivity of 8–10 kHz cm 2/ng.

ZnO-based film bulk acoustic resonator for high sensitivity biosensor applications

Zinc oxide (ZnO)-based film bulk acoustic resonator consisting of a piezoelectric element (Au∕ZnO∕Pt) and a Bragg reflector (ZnO∕Pt multilayer structure) has been fabricated by magnetron sputtering. The transmission electron microscopy and x-ray diffraction measurements revealed that all thin film layers in the device were well crystallized and highly textured. By electrical measurements, it was found that the device had a high resonant frequency (3.94GHz) and mass sensitivity (8970Hzcm2∕ng). The use of the device as a biosensor was demonstrated by comparing the resonant properties of the device with/without coatings of biospecies.

Fabrication and Characterization of ZnO-Based Film BulkAcoustic Resonator with a High Working Frequency

We report on the fabrication and characterization of a ZnO-basedfilm-bulk acoustic-resonance device utilized as biosensor. Thedevice has a multilayer structure which consists of piezoelectricelement (Au/ZnO/Pt) and a Bragg-reflection-layer acoustic isolationconsisting of multilayers of ZnO/Pt. Dielectric measurements haverevealed that the device has a very high working frequency (up to~3.1 GHz), meaning that the device may have a higher sensitivitythan the devices reported in the literature.

Effects of thermal annealing of W/SiO2 multilayer Bragg reflectors on resonance characteristics of film bulk acoustic resonator devices with cobalt electrodes

In this article, we present the thermal annealing effects of the W/SiO2 multilayer reflectors in ZnO-based film bulk acoustic resonator (FBAR) devices with cobalt (Co) electrodes in comparison with those with aluminum (Al) electrodes. Various thermal annealing conditions have been implemented on the W/SiO2 multilayer reflectors formed on p-type (100) silicon substrates. The resonance characteristics could be significantly improved due to the thermal annealing and were observed to depend strongly on the annealing conditions applied to the reflectors. Particularly, the FBAR devices with the W/SiO2 multilayer reflectors annealed at 400 °C/30 min have shown superior resonance characteristics in terms of return loss and quality factor. In addition, the use of Co electrodes has resulted in the further improvement of the resonance characteristics as compared with the Al electrodes. As a result, the combined use of both the thermal annealing and Co electrodes seems very useful to more effectively improve the resonance characteristics of the FBAR devices with the W/SiO2 multilayer reflectors.

Significant resonance characteristic improvements by combined use of thermal annealing and Co electrode in ZnO-based FBARs

Resonance characteristics improvements by the combined use of thermal annealing of the W/SiO2 Bragg reflectors and Co electrodes in ZnO-based film bulk acoustic resonator (FBAR) devices are presented. Their resonance characteristics could be significantly improved by the thermal annealing particularly at 400°C/30 min. In addition, the use of Co electrodes has resulted in further improvement of the resonance characteristics, compared to the use of Al electrodes.

Improvements of resonance characteristics due to thermal annealing of Bragg reflectors in ZnO-based FBAR devices

The effects of thermal annealing of W/SiO2 multilayer Bragg reflectors on the resonance characteristics of ZnO-based film bulk acoustic resonator (FBAR) devices are presented for the first time. The resonance characteristics could be significantly improved due to thermal annealing. FBAR devices with Bragg reflectors annealed at 400°C/30 min show excellent resonance characteristics in terms of return loss and Q-factor.

Fabrication of ZnO-based film bulk acoustic resonator devices using W/SiO2 multilayer reflector

A ZnO-based film bulk acoustic resonator (FBAR) with a W/SiO2 multilayer reflector has been fabricated using a two-step ZnO deposition. The FBAR showed a large return loss of 35 dB at ~2 GHz and a high quality factor (high-Q) of ~4000. The resonance characteristics depended largely on the multilayer reflector and ZnO film.