Compensated Surface Acoustic Wave Research Articles

Double Metal Dots Configuration for Suppression of Spurious Responses in Temperature Compensated Surface Acoustic Wave Resonators on SiO2/LiNbO3 Structure

Double Metal Dots Configuration for Suppression of Spurious Responses in Temperature Compensated Surface Acoustic Wave Resonators on SiO₂/LiNbO₃ Structure

Suppression of spurious responses near anti-resonance of TC-SAW resonators by selective thinning of SiO2

This paper discusses the generation mechanism and suppression of spurious resonances near the anti-resonance in temperature compensated surface acoustic wave devices using the SiO2/128°YX-LiNbO3 structure. Detailed field analysis is performed for the spurious resonances, and the result indicates that the spurious modes are caused by excitation and/or scattering near the electrode finger edges, and can be suppressed well by thinning of the SiO2 layer selectively in the gap region. It is also shown that most of spurious responses can be suppressed for the piston design using the Cu dots with the SiO2 selective thinning. In contrast, this selective SiO2 thinning does not work well for the piston design using the Cu stripes.

Influence of displacement and patterning of phase shifters for piston mode operation of temperature compensated surface acoustic wave resonators on SiO2/LiNbO3 structure

This paper discusses the influence of displacement and patterning of phase shifters for piston mode operation of the temperature compensated surface acoustic wave (SAW) resonator on SiO2/LiNbO3 structure. As the phase shifters, Cu metals placed on the top surface of SiO2 are considered. First, the conventional Cu stripes are chosen, and their displacement is considered from interdigital transducer (IDT) aperture edges. It is shown that achievable transverse mode suppression is almost identical when the stripe shape is adjusted for each case. Next, Cu dots are considered as patterned phase shifters. It is shown comparable transverse mode suppression is possible also for this case. However, relatively strong SAW lateral leakage occurs when they are placed above IDT fingers. These results indicate that location and pattern can be added as design parameters for the phase shifters on SiO2. It is favorable for further enhancement of total device performances.

Study of loss mechanisms in temperature compensated surface acoustic wave devices based on finite element method analysis using hierarchical cascading technique

This paper discusses loss mechanisms of temperature compensated surface acoustic wave (TC-SAW) devices using the SiO2 overcoated 128°YX-LiNbO3 (128-LN) substrate. Analysis is based on the finite element method (FEM) combined with the hierarchical cascading technique and the general purpose graphics processing unit. Three kinds of FEM model, i.e. 2.5D, three dimensional (3D) periodic and full 3D are analyzed without taking additional losses, i.e. material viscous loss, dielectric loss and electrode ohmic loss, and influence of scattering at structural discontinuities is evaluated solely. It is shown that although Q reduction is significant with an increase of the simulation dimension, in other words, that of the number of acoustic scattering mechanisms, estimated Q value is still considerably higher than reported values even for full 3D simulation. This result indicates that acoustic scattering at structural discontinuities is not a dominant loss mechanism in current TC-SAW devices employing the SiO2 overcoated 128-LN substrate.

Predicted and measured temperature compensated surface acoustic wave devices for high‐temperature applications

Industrial monitoring and process control, power plants, aerospace industry, military equipment manufacturing, oil and gas industries are examples of businesses in need for high-temperature and harsh-environment electronic components and systems. In particular, resonators and filters that operate beyond the 125°C military range upper limit, normally dictated by silicon-based semiconductor devices, are required in applications which demand frequency control, clocking and sensors. In this Letter, temperature compensated surface acoustic wave orientations appropriate for the fabrication of resonators and filters >125°C have been identified through numerical calculations and experimentally confirmed on a commercially available langasite wafer, a piezoelectric crystal which operates at high temperatures. Resonator filters have been designed, fabricated and tested along two orientations, confirming the zero temperature sensitivities at 150 and 300°C. These devices are of great interest for modern harsh environment frequency control, timing and sensor applications.

Operation modes of the FALCON ion source as a part of the AMS cluster tool

Abstract The paper investigates the options to increase the production yield of temperature compensated surface acoustic wave (SAW) devices with a defined range of operational frequencies. The paper focuses on the preparation of large wafers with SiO2 and AlN/Si3N4 depositions. Stability of the intermediate SiO2 layer is achieved by combining high power density UV radiation with annealing in high humidity environment. A uniform thickness of the capping AlN layer is achieved by local high-rate etching with a focused ion beam emitted by the FALCON ion source. Operation parameters and limitations of the etching process are discussed.

2Pb3-5 Optimization of SiO_2 Films and Application of Fluorine Doped SiO_2 Films for Temperature Compensated Surface Acoustic Wave Devices(Poster Session)

2Pb3-5 Optimization of SiO_2 Films and Application of Fluorine Doped SiO_2 Films for Temperature Compensated Surface Acoustic Wave Devices(Poster Session)

Two-step metalorganic chemical vapor deposition growth of piezoelectric ZnO thin film on SiO2/Si substrate

Piezoelectric ZnO thin films deposited on semiconductor substrates are used for surface and bulk acoustic wave and devices, which offer advantages such as low power consumption, circuit miniaturization, and cost reduction by integration with microwave monolithic integrated circuit technology. Furthermore, temperature compensated surface acoustic wave (SAW) devices, which are attractive for both communication and sensor technologies, may be achieved in the ZnO/SiO2/Si system as ZnO and Si have positive temperature coefficients of delay, while SiO2 has a negative one. In the present work, ZnO thin films were grown on SiO2/Si substrates by metalorganic chemical vapor deposition. The structural properties of the films were investigated using x-ray diffraction, scanning electron microscopy, and scanning probe microscopy. A two-step growth process was developed to obtain ZnO films with both good crystalline quality and surface morphology. The SAW properties of the ZnO/SiO2/Si system were investigated through modeling and computer simulation based on the transfer matrix method. Acoustic velocity dispersion data obtained from measurement on testing structures agree well with the dispersion curves predicted by computer simulation. The results show that the ZnO/SiO2/Si system is promising for fabricating low-loss SAW devices.

Surface acoustic wave devices and method of manufacture thereof

A phase and amplitude compensated surface acoustic wave (SAW) structure is described in which computer controlled compensation is achieved by laser chemical etching of selective portions of a compound chemical film deposited on the surface of a piezoelectric SAW substrate in the path of propagation. The compound film comprises a layer of amplitude attenuating cermet material formed on the substrate and a phase compensating layer of molybdenum formed over the cermet material and in contact with the substrate surface.

Acceleration Stress Compensated Surface Acoustic Wave Devices

Acceleration Stress Compensated Surface Acoustic Wave Devices