High Quality Silicon-Based AlN Thin Films for MEMS Application

ABSTRACT

Aluminum nitride is an attractive piezoelectric material for MEMS devices such as bulk acoustic wave (BAW) devices. (002)-oriented AlN films were deposited on Si, Al and Pt by reactive sputtering. Optimized AlN (002) peak reaches a full width at half maximum (FWHM) of 5.6°. Auger electron spectroscopy is used to analyze the oxygen contamination of films. To find the suitable electrode material for device application, the growth mechanism of AlN crystallites on different substrates is also discussed. Based on sputtered AlN films, the prototype of AlN thin film bulk acoustic resonator (TFBAR) was fabricated successfully.     

High frequency response of Bragg reflector type film bulk acoustic wave resonator

Abstract

We fabricated a Bragg reflector type FBAR using AlN piezoelectric with quarter wavelength thickness, where the Bragg reflector was composed of W-SiO₂ pairs. By numerical simulation considering actual acoustic losses of each layer, we analyzed the frequency response of the resonator and could explain it using an equivalent circuit with parasitic elements. The Effective electromechanical coupling constant (K ² _eff ) and the Quality factor (Q_s ), figures of merit of the resonator, were about 1.1% and 307, respectively.</ab>     

Characterization of dielectric and acoustic properties of CSD PZT thin films at high frequencies

In this study, the microwave dielectric and the acoustic properties of Pb(Zr _x ,Ti_1-x )O₃ (PZT) thin films deposited using chemical solution deposition (CSD) were investigated using the same measurement setup. High dielectric constants in the range of ~280–540 and loss tangents less than 0.1 at 4 GHz were measured, where the value depends on the thickness of the PZT film. The voltage tunability of the 340 nm and 440 nm thick PZT thin films was ~34% and 5% for the 140 nm thick PZT film at 120 kV/cm and 4 GHz. The acoustic parameters of the PZT thin films under DC bias voltages were determined using a one-dimensional acoustic wave resonator model. For the PZT films of thicknesses 340 nm and 440 nm, the acoustic resonance frequency shift was about 15 MHz and the electromechanical coupling coefficient was ~10% at an electric field of 160 kV/cm. The large dielectric constant and high tunability suggest that the characterized PZT thin films may be suitable for radio frequency (RF) applications such as high-density RF MIM capacitors and other tunable devices.     

PREPARATION OF HIGHLY TEXTURED ALN FILMS USING MO AND TI ELECTRODE FOR INTEGRATED ALN-BASED FILM BULK ACOUSTIC WAVE RESONATORS

ABSTRACT

Effect of buffer layer on the characteristics of the AlN thin films deposited on SiNx/Si substrate was systematically examined. Among the buffer layers examined, both Mo and Ti buffer layers can not only greatly enhance the (002) preferred orientation of the films, but also improve the smoothness of the AlN films, whereas the Al thin films contain large grains microstructure and resulting in rough surface and wide distribution of (002) preferred orientation of the films. AlN thin films with smooth surface with (r.m.s. < 6 nm) and narrow distribution of grains' orientation (rocking curve < 3.8°), which is suitable for fabricating the devices. A thin film bulk acoustic wave resonator with resonance frequency around 1.7 GHz was fabricated from thus obtained AlN thin films.     

燃煤可吸入颗粒物在驻波声场中动力学特性的研究

为研究可吸入颗粒物PM 2.5在声波场中的动力学特性, 利用可视化技术建立研究颗粒物动力学特性的实验装置。采用电厂飞灰作为颗粒源，利用高速CCD摄像机动态地显微拍摄颗粒在水平声场中的运动轨迹，并结合数值方法理论模拟颗粒的运动轨迹。结果显示颗粒在驻波场的波节点处不振动、不飘移；波腹处只振动、不飘移；其余各点处的颗粒既振动、也向波节方向漂移，并与竖直方向的运动叠加，形成在声场中的运动轨迹。颗粒振动频率与声波频率相同，但因颗粒存在惯性，振动速度幅值小于声波速度幅值，且相位滞后。动力学特性的结果显示：振动使得颗粒在单位时间内扫过的面积大大增加，有利于颗粒间的碰撞团聚；漂移特性有利于颗粒间的碰撞和气流中颗粒的分离。     

Behavior of magneto‐acoustic waves in a nonequilibrium subsonic disk MHD generator

The behavior of magneto‐acoustic waves in a nonequilibrium subsonic disk MHD generator was examined. The solution of the sixth‐order dispersion relation obtained by linearizing the set of MHD equations suggested that a magneto‐acoustic wave which propagates at a velocity of u_r ? a(u_r: radial fluid velocity, a: sound velocity) should be damped in subsonic flow. From time‐dependent quasi‐one‐dimensional simulations, it was verified that the pressure disturbance in the subsonic generator was damped at approximately the same rate as the value predicted by the linear theory. From a simplified analytical model, the mechanism of magneto‐acoustic instability with fully ionized seed was discussed, and the damping criterion for the magneto‐acoustic wave was clarified. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 142(4): 20–26, 2003; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10108     

Application of TiO<Subscript>2</Subscript> thin film with nanorods to surface acoustic wave type ultraviolet photo detection

TiO₂ thin films with nanorods grown on 128° Y?cut LiNbO₃ and 90° rotated 42°45′ ST?cut quartz were used to fabricate surface acoustic wave ultraviolet photodetectors. TiO₂ thin film was deposited by radio?frequency magnetron sputtering and TiO₂ nanorods were then synthesized on the thin film via the hydrothermal method. 128° Y?cut LiNbO₃ is a Rayleigh wave substrate with a high electromechanical coupling coefficient, whereas 90° rotated 42°45′ ST?cut quartz is a surface skimming bulk wave substrate with a high wave velocity. The effects of substrate characteristics and TiO₂ nanorod morphology on the ultraviolet sensitivity of the surface acoustic wave photodetectors were investigated. The variations of insertion loss, phase, resistance, and capacitance under ultraviolet illumination were examined. The performance of the TiO₂ thin film with nanorods deposited on 128° Y?cut LiNbO₃ is much greater than that of the film deposited on 90° rotated 42°45′ ST?cut quartz, which can be attributed to the former’s high electromechanical coupling coefficient.     

用于传感器的声表面波谐振器耦合模理论研究

本文主要研究声表面波耦合模理论在声表面波谐振器中的应用。本文结合声表面波谐振器的特点，对谐振器表面沉积介质薄膜后引起器件结构参数的变化进行了分析，为研究基于ＳＡＷ谐振器的传感器提供了一种方法。     

Signal Propagation on Single Phase Power Distribution Lines at Power Line Carrier Frequencies

Two sets of propagation measurements were made on a 20,847 foot unenergized power distribution line in the frequency range 0 to 50 kHz. The line was configured with and without distribution transformers. From the first set of measurements a voltage transfer function was calculated for this line. In the second set of measurements the line was energized with a 25 kHz signal and the voltage, current and impedance were measured along the line. Various propagation characteristics such as attenuation, characteristic impedance, velocity of propagation, and standing wave ratios were determined from these measurements.     

Reflection-Type Ferroelectric Phase Shifter With Defected Ground Structure

In order to obtain a low-loss ferroelectric phase shifter, we were designed and fabricated the reflection-type ferroelectric phase shifter with the defected ground structure (DGS) resonators. The ferroelectric phase shifter is consisted of a 3-dB 90° branch-line hybrid coupler and terminated reflective circuit with tunable ferroelectric DGS resonator which can provide a high Q resonator characteristic at high frequencies. The design parameters of equivalent circuit for the tunable DGS resonator are derived by circuit analysis method and three-dimensional full wave finite element method. At 13.5 GHz, the fabricated phase shifter exhibited an insertion loss of better than 3.4 dB.     

RF Bulk Acoustic Wave Resonators and Filters

Small sized, highly selective solidly mounted bulk acoustic wave (BAW) band pass filters are of great interest for mobile and wireless systems operating in the frequency range of 0.8 GHz up to more than 10 GHz. They can be fabricated on silicon or glass wafers using standard semiconductor integration techniques. These filters are based on electro-acoustic high Q resonators, which exploit the thickness extensional mode of a thin piezoelectric AlN or ZnO film. This film has to be grown with its polar axis, oriented perpendicular to the substrate. Both the deposition process and using a textured electrode support excellent c-axis oriented growth and thus high electromechanical coupling coefficient k _t and filter bandwidth. Modelling of the filter and resonator response is performed by means of a combination of a 1D electro-acoustic model together with an electromagnetic model. The paper shows examples of filters operating in the range between 2 and 8 GHz.     

Modeling of a wireless saw temperature sensor and associated antenna

Surface acoustic wave (SAW) resonator used as wireless sensor was characterized and the parameters of its MBVD ((Modified Butterworth-Van Dyke) model were extracted versus temperature. The extracted parameters lead to evaluate the resonator performances in terms of Temperature coefficient of frequency (TCF) and quality factor (Q). An antenna was then associated with the SAW resonator and the entire system has been characterized and modeled. The good agreement experiment-simulation allows to define the optimum operating conditions of the wireless sensor.     

Reliability of velocity pulsatility in small vessels on 3Tesla MRI in the basal ganglia: a test–retest study

Objective

Recent work showed the feasibility of measuring velocity pulsatility in the perforating arteries at the level of the BG using 3T MRI. However, test–retest measurements have not been performed, yet. This study assessed the test–retest reliability of 3T MRI blood flow velocity measurements in perforating arteries in the BG.

Materials and methods

Two-dimensional phase-contrast cardiac gated (2D-PC) images were acquired for 35 healthy controls and repeated with and without repositioning. 2D-PC images were processed and analyzed, to assess the number of detected perforating arteries (N_detected), mean blood flow velocity (V_mean), and velocity pulsatility index (vPI). Paired t-tests and Bland–Altman plots were used to compare variance in outcome parameters with and without repositioning, and limits of agreement (LoA) were calculated.

Results

The LoA was smallest for V_mean (35%) and highest for vPI (79%). Test–retest reliability was similar with and without repositioning of the subject.

Discussion

We found similar LoA with and without repositioning indicating that the measurement uncertainty is dominated by scanner and physiological noise, rather than by planning. This enables to study hemodynamic parameters in perforating arteries at clinically available scanners, provided sufficiently large sample sizes are used to mitigate the contribution of scanner- and physiological noise.

     

Mode‐matching analysis of a spit‐circular cavity resonator for measurement of the dielectric constant for film on a substrate

In this paper, we apply the mode‐matching technique (eigenmode expansion) to formulate an analytical model for a split cylindrical cavity resonator with a thick ceramic film layer sandwiched between two‐layer alumina substrates. We then compute the resonant frequencies with the TE₀₁₁ mode with an eigenvalue problem approach using the model formula. The quality factor (Q ‐factor) of the resonator is also calculated by applying the perturbation method to the analytical model. The validity of the proposed analytical technique is confirmed by applying this method to the estimation of permittivity of thick films as an inverse problem. Ceramic films (2 µm thickness) were synthesized using a chemical solution method onto 200‐µm‐thick, 50‐mm‐diameter alumina substrates. The complex permittivity of the films was then determined using the TE₀₁₁ mode split cylindrical cavity resonator in the 10‐GHz band. The extent of the edge effect at a sample insertion space was evaluated by comparing the estimated results through TE wave analysis using the mode‐matching method when the transverse resonance technique and the perturbation method were applied to calculate the resonant frequency and the dielectric Q ‐factor. The results obtained indicate that a difference of 0.153% in the permittivity of the alumina substrate causes differences of 6.10 and 3.75% in the measured permittivity and loss tangent, respectively, of 2‐µm‐thick ceramic film with a permittivity of ∼50. Differences in permittivity and loss tangent were more pronounced with thinner films. It was also confirmed that the estimated results for permittivity and the loss tangent values of these ceramic films were affected by the estimated permittivity value of the alumina substrate. © 2017 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

High‐aspect‐ratio aluminum‐doped zinc oxide nanomechanical resonator

This paper reports on the patterning of a high‐aspect‐ratio aluminum‐doped zinc oxide (AZO) capacitive resonator based on the combination of the deep reactive ion etching (deep RIE) and atomic layer deposition (ALD) processes. The suspended AZO capacitive resonator is successfully demonstrated. Its resonant frequency is observed at 10.4 kHz with a quality factor (Q factor) of approximately 500 in a vacuum chamber.     

Vibrational Torques in Single-Phase Induction Motors and Their Relation to Vibration and Noise

ABSTRACT

The general torque equation of single-phase induction motors has been extended to account for the vibrational torques, which include not only the twice supply frequency component but also other significant harmonics. The effect of the tangential vibrations on the emitted acoustic noise is investigated and is verified against measurements on an electrical fan.     

变压器特高频、超声波侵入式PD联合检测技术

最新颁布的IEC TS 62478-2016《高电压技术-电磁和声学法测量局部放电》国际标准,指出了现有的外置式超声波法测量PD主要存在:设备外壳对声波的衰减和不同介质声阻抗引起的传输多路径问题。笔者基于变压器放油阀结构,将特高频(UHF)天线和压电陶瓷声发射(AE)传感器进行一体化设计,再考虑电磁波和超声波信号耦合、防变压器油渗漏两个主要问题的基础上,加工研制了能够同时耦合UHF、AE信号的侵入式PD复合传感器。110 kV变压器内置尖端放电下与外置式压电陶瓷AE传感器的对比试验表明:所设计的UHF、AE侵入式PD复合传感器能够有效探测到油中微弱放电产生的具有特定时间差Δt的电磁波和超声波信号,这为变压器PD检测提供了一种全新的"声-电"即UHF、AE联合检测技术。     

LOCAL ELASTICITY RESPONSE IN FERROELECTRIC CRYSTALS STUDIED BY AFM-BASED NOVEL PROBE TECHNIQUES

ABSTRACT

A novel probe technique, low frequency scanning probe acoustic microscope, was firstly developed based on the commercial atomic force microscope. The excitation frequency is in the range of several kHz up to teen-kHz, which is much lower than that in the conventional acoustic microscopes. The acoustic images of nanoscale domain structures in Pb(Mg_1/3Nb_2/3)O₃-33%PbTiO₃ single crystals were successfully visualized. Different electric polarizations show the variation of the elasticity in ferroelectrics, so the contrast of the acoustic images reflects the domain structure or the subsurface elasticity. In addition, the elasticity of the sample in response to the modulation of the excitation source is also discussed.     

基于时频分量相关分析的高压电缆双端行波测距

高压电缆行波测距需解决2个关键问题:确定行波到达时刻和选取行波波速。由于线路存在损耗且参数随频率变化,导致行波在传播过程中存在波形畸变,不易确定行波到达时刻;另外由于不同频段的波速不同,因此不易选取一个固定的行波波速。针对以上问题,利用正交小波的频段剖分功能和适合表征暂态信号的特点,将暂态行波信号分解成多个频段内的时频分量信号。在各个频段,线路的衰减系数和波速都可近似为常数,因此各频段两侧的时频分量波形相似。用相关分析方法在各个频段确定两侧行波时频分量的时间差,结合各个频段内的波速,即可得出精确的双端行波故障测距结果。用EMTDC仿真对该方法进行了实验验证。     

The NMR sensitivity achievable with a slotted-tube resonator

The signal-to-noise ratio achievable with the slotted-tube resonator (STR), a fundamental type of high radiofrequency coil for nuclear magnetic resonance (NMR) experiments, was formulated in an equation. This equation is based on formulae presented by Hoult and Richards [J Magn Reson 24, 71 (1976)] and Hoult and Lauterbur [J Magn Reson 34, 425 (1979)]. The equation assumes that the sample is positioned within the homogeneous region of magnetic fluxB ₁ generated by the STR, and involves no unknown factors. The NMR sensitivity of an experiment with an STR can therefore be predicted, and the equation is applicable to any nuclear species, static field strength, and dimensions of the sample and STR.