Surface Acoustic Wave Device With Pt Or W Electrodes

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Solution Overview

Problem

Surface acoustic wave devices using IDTs on LiTaO3 or LiNbO3 substrates face limitations in achieving high electromechanical coupling coefficients and superior resonant characteristics due to restricted Euler angles and negative reflection coefficients, which hinder their performance as resonators or band pass filters.

Innovation Solution

A surface acoustic wave device utilizing an LiNbO3 substrate with Pt or W electrodes and an SiO2 dielectric film, where the electrode thickness and Euler angles are optimized to enhance the electromechanical coupling coefficient K2, increasing the range of usable Euler angles and improving device characteristics.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If Al is used as the IDT electrode material on LiTaO3 substrate, then the device structure is simple, but the electromechanical coupling coefficient is limited and the range of usable Euler angles is restricted

Engineering Contradiction:

Improvedevice structureVSAvoidelectromechanical coupling coefficient

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The patent changes the electrode material parameter from Al to Pt or W, which have higher densities and different acoustic properties. This parameter change increases the electromechanical coupling coefficient and expands the range of Euler angles that can be used with LiNbO3 substrates, overcoming the limitations of Al-based devices

Inventive Principle:

Principle #35Parameter changes

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The solution achieves a high reflection coefficient and electromechanical coupling coefficient K2, expanding the design freedom and performance of surface acoustic wave devices by optimizing electrode materials and configurations, particularly with Pt or W electrodes and SiO2 films, leading to improved resonant and filtering capabilities.

Implementation Method 1

an IDT including a plurality of electrode fingers made of a metal material which is filled in the plurality of grooves in the upper surface of the piezoelectric substrate, and the metal material is Pt or W

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Implementation Method 2

An SiO2 film is laminated so as to cover the upper surface 1002a of the LiTaO3 substrate 1002

Methodology Applied

Scientific EffectDielectric property: Dielectric

Data Source

PatentUS7956512B2Surface acoustic wave device including an IDT formed by a metal filled in grooves on a piezoelectric substrate

Publication Date: 2011.06.07 MURATA MFG CO LTD

AI summary

A surface acoustic wave device includes a LiNbO3 substrate and is constructed such that the reflection coefficient of an IDT is not only high but the electromechanical coupling coefficient K2 is also high, and the range of Euler angles of the LiNbO3 substrate can be increased to realize a wide range of the electromechanical coupling coefficient K2. A plurality of grooves are provided in an upper surface of the LiNbO3 substrate, an IDT including a plurality of electrode fingers is provided by filling a metal material in the plurality of grooves, and the metal material is Pt or W or an alloy primarily including at least one Pt or W.