Energy-trapped shallow bulk acoustic waves

A low-loss high-sidelobe-rejection shallow bulk acoustic filter has been constructed. The delay line consisted of apodised and finger-withdrawal-weighted transducers as well as a metallic energy-trapping grating. Experimental results are given and discussed.     

Electromagnetic modeling of thin-film bulk acoustic resonators

This paper introduces a novel technique for the electromagnetic analysis of thin-film bulk acoustic-wave resonators. The piezoelectric/acoustic linear equations are coupled to and solved together with Maxwell's equations. For the acoustic propagation, locally monodimensional behavior is assumed, while full-wave three-dimensional Maxwell's equations are rigorously solved for the complete circuit. The proposed approach is validated for single resonators by comparison with experimental data, providing very good agreement with reduced computational resources. Hence, a complete Agilent Technologies' nine-resonator passband filter is simulated in order to demonstrate a typical application to a real-world complex problem.     

Acousto-optic interaction in the lithium niobate crystal upon the surface excitation of the bulk acoustic wave

The interaction of light with the bulk acoustic wave that is excited from the surface of the lithium niobate crystal is experimentally studied. A prototype of the acousto-optic device that employs the XY-cut crystal and the optimized (Y-13°)-cut crystal is presented. Diffraction efficiencies of 1 and 2 %/W are obtained for the first and second prototypes, respectively. It is demonstrated that the polarization characteristics of the device differ from the conventional characteristics by the dependence on the structure of the acoustic beam. An original method for the excitation of the ultrasonic beam can be used in the acousto-optic devices for light control.     

An insulated shallow extension structure for bulk MOSFET

This brief proposes possible a replacement of shallow p-n junction with insulated shallow extension (ISE) structure for bulk MOSFET. The shallow extension is defined by the sidewall thermal oxide rather than the implanted p-n junction. With this insulator for extension and main junction, a heavier halo doping concentration can be used. Thus, the threshold-voltage roll-off and the junction leakage current can be minimized simultaneously. This structure can be a good alternative for junction structures in sub-100-nm regimes.     

AIN薄膜体声波谐振器性能分析

采用体硅微细加工工艺制备了背空腔型AIN薄膜体声波谐振器。研究了压电层、上电极及支撑层厚度对谐振器性能的影响。测试结果表明，谐振器所用AIN压电薄膜具有（002）择优取向，器件频率特性良好。当上电极、压电层、底电极和支持层的厚度分别为110，2600，110，200nm时，谐振频率为1．759GHz，机电耦合系数3．75％，品质因数79．5。结合Mason等效电路模型模拟分析与实验结果，分析了各层厚度对频率特性的影响机理。     

AlN薄膜体声波谐振器性能分析

采用体硅微细加工工艺制备了背空腔型AlN薄膜体声波谐振器。研究了压电层、上电极及支撑层厚度对谐振器性能的影响。测试结果表明,谐振器所用AlN压电薄膜具有(002)择优取向,器件频率特性良好。当上电极、压电层、底电极和支持层的厚度分别为110,2600,110,200nm时,谐振频率为1.759GHz,机电耦合系数3.75%,品质因数79.5。结合Mason等效电路模型模拟分析与实验结果,分析了各层厚度对频率特性的影响机理。     

Generation of 880 MHz surface acoustic wave by transduction from bulk wave using corrugation grating on GaAs

Efficient transduction from bulk to surface waves by a holographic grating on a GaAs crystal has been demonstrated. The beam profiles for 880 MHz surface waves propagating on the GaAs were measured by an optical probing method.     

Simulation and fabrication of thin film bulk acoustic wave resonator

In this paper, we present the simulation and fabrication of a thin film bulk acoustic resonator (FBAR). In order to improve the accuracy of simulation, an improved Mason model was introduced to design the resonator by taking the coupling effect between electrode and substrate into consideration. The resonators were fabricated by the eight inch CMOS process, and the measurements show that the improved Mason model is more accurate than a simple Mason model. The Q_s (Q at series resonance), Q_p (Q at parallel resonance), Q_max and k_t² of the FBAR were measured to be 695, 814, 1049, and 7.01% respectively, showing better performance than previous reports.     

Temperature-compensated film bulk acoustic resonator above 2 GHz

Two different types of temperature-compensated film bulk acoustic resonators (FBARs) are designed, fabricated, and tested. One is formed by integrating FBAR with a surface-micromachined air-gap capacitor, which passively reduces the FBAR's temperature coefficient of frequency (TCF) by about 40 ppm//spl deg/C at 2.8 GHz. With this approach, zero TCF would easily have been achieved if the FBARs were built on AlN rather than ZnO. The other type of temperature compensated FBAR is built on a surface-micromachined SiO/sub 2/ cantilever that is released by XeF/sub 2/ vapor etching of silicon. The Al-ZnO-Al-SiO/sub 2/ FBAR is measured to have a TCF of -0.45 ppm//spl deg/C (between 85/spl deg/C and 110/spl deg/C) at 4.4 GHz.     

Convolution and correlation using light diffraction from bulk acoustic waves

Bulk acousto-optic signal processors using simultaneous light diffraction in high-figure-of-merit materials are described in the letter and some experimental results are reported.     

Crystal growth and properties of TI3BX4 crystals for acoustic surface-wave and bulk acoustic devices

Crystals of Tl₃TaS₄ and T1₃Tase₄ possess properties which indicate that they could be extremely useful for acoustic devices. They are piezoelectric, have low acoustic velocities (6.89 to 8.53 x 10₄ cm/sec), high effective values of electromagnetic coupling (k² up to ~ 3%) and contain directions in which the thermal coefficients of delay are zero. Materials preparation and crystal growth and properties are described.     

Visualisation of surface acoustic waves

A simple method for acoustic-surface-wave visualisation is described which is applicable to both piezoelectric and non-piezoelectric surfaces. Briefly, a uniform layer of small particles, comparable to the wavelength, is distributed over the acoustic surface. The acoustic-beam pattern of an incident surface wave is then traced out by scattering the particles out of the propagation path. Experiments at 100 MHz on lithium-niobate surfaces are described.     

Method for improving ladder bulk acoustic wave filters rejection

This paper address design guidelines for improving the rejection of ladder bulk acoustic wave filters. An overview of the bulk acoustic wave filters technology enables to outcome the principal features of ladder filters. The lack of out-of-band rejection is currently an important weakness of this topology. The design technique presented enables to improve bulk acoustic wave ladder filters rejection by using their input/output bonding wires. Finally, the technique is used for design and fabrication of a bulk acoustic wave ladder filter for application in W-CDMA reception (2.11–2.17 GHz) front-ends. The filter measurement results show a significant improvement on the filter rejection at the transmission band (from ?19 to 34 dB) and on the return loss (from ?10 to ?16 dB) without considerable modification of filter insertion loss and selectivity.     

一种射频体声波滤波器的版图设计与仿真

射频体声波滤波器品质因子高,尺寸小,其性能已超过声表面波滤波器,将其替代传统的射频滤波器极具性能和价格优势。本文建立了适用于体声波滤波器性能分析的巴特沃斯—范戴克（MBVD）模型,采用梯形级联方式设计了一种射频体声波滤波器的版图。在此基础上以中心频率为1.99GHz,带宽56MHz的体声波滤波器为例,对不同连接级数梯形滤波器的插入损耗、阻带抑制进行了仿真与分析讨论,在4阶滤波器中其带外衰减达到了-29.708dB。采用微机电机械系统工艺制备的2阶和3阶滤波器传输特性的测试曲线与仿真结果基本吻合,表明射频体声波滤波器具有广泛的应用前景。该模拟结果可作为射频体声波滤波器设计的一个重要参考。     

MEMS-IDT声表面波陀螺

声表面波陀螺的概念出现在70年代初期,发展为MEMS-IDT声表面波陀螺仅是最近几年的事情。MEMS-IDT声表面波陀螺仪是一种MEMS微机械振动陀螺,这种陀螺为单层平面结构,采用标准IC工艺就可完成加工,勿需悬浮的振动元件,有很强的抗冲击振动能力,可靠性高,可不用真空封装而保持较高的灵敏度。     

Practical surface acoustic wave devices

A tutorial discussion is presented on selected surface acoustic wave (SAW) devices for the use of engineers and electronic systems designers. Currently practical components for use in radar systems, communications systems, and as frequency domain filters are described. Emphasis is placed on nondispersive and dispersive delay lines, devices for generating and detecting various radar waveforms, devices for generating and detecting fixed and programmable biphase and multiphase codes, and broad-band and narrow-band filters. The device possibilities of several new approaches are described, including multistrip couplers, nonlinear convolvers, reflective structures, and overlay films. It is concluded that, while SAW devices have found many applications in large radar systems because of their size, cost effectiveness, and reliability, wide-scale applications, for example as frequency domain filters, will be needed to justify continued research in this field. Wide-scale applications will come as systems engineers realize the potential of these devices and confidently design them into their systems.     

High-stability acousto-optical devices using bulk acoustic waves in TeO2

Acousto-optical devices are currently being developed for various applications, including laser Doppler anemometers (l.d.a.s.)     

Optical probing of surface acoustic waves

Light diffraction by surface acoustic waves is used in studying the propagation characteristics of Rayleigh waves on y-cut z-oriented LiNbO3. In reflection, only the surface deformation contributes to the diffracted light. In transmission, the photoelastic effect, which is incident beam polarization dependent, must also be considered. Such optical probing has been used to study the Fresnel diffraction radiation pattern of an interdigital transducer, to measure beam steering effects related to transducer misalignment on an anisotropic substrate, and to measure reflection and transmission coefficients of an electrically loaded transducer. Attenuation measurements have been made over frequencies as high as 3.5 GHz. The power dependence of attenuation and harmonic generation is also examined.     

Wavefront visualisation of acoustic surface waves

Acoustic surface waves (a.s.w.) propagating on yz-cut lithium niobate have been visualised by two imaging techniques. The wavefronts of straight-crested and convergent a.s.w. have been rendered visible on the screen of a storage oscilloscope.