Multilayer IDT Electrode for SH-SAW Transverse Leakage Suppression

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Solution Overview

Problem

Existing surface acoustic wave devices with low cut angle lithium niobate piezoelectric layers suffer from degraded quality factor and transverse leakage, which degrades their performance in radio frequency applications.

Innovation Solution

The acoustic wave device incorporates a multilayer interdigital transducer electrode with a first layer having a higher density material, such as tungsten, positioned between the piezoelectric layer and a second layer with a lower density material, such as aluminum, to enhance the frequency response and suppress transverse leakage, while a temperature compensation layer and dispersion adjustment layer are used to improve electromechanical coupling and quality factor.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a low cut angle lithium niobate piezoelectric layer is used, then the electromechanical coupling coefficient is improved, but the quality factor is degraded and transverse leakage occurs

Engineering Contradiction:

Improveelectromechanical coupling coefficientVSAvoidquality factor

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The interdigital transducer electrode is divided into multiple layers (first layer and second layer) with different materials and thicknesses. The first layer has higher density and the second layer has lower density, creating a segmented structure that independently optimizes different aspects of device performance.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different layers of the electrode are assigned different local properties: the first layer is designed with specific density and thickness to suppress transverse leakage locally, while the second layer is optimized for electrical connectivity. This local optimization resolves the contradiction between coupling coefficient and quality factor.

Inventive Principle:

Principle #3Local quality

2Adaptability or versatility

If a low cut angle lithium niobate piezoelectric layer is used, then the electromechanical coupling coefficient is improved, but transverse leakage degrades performance

Engineering Contradiction:

Improveelectromechanical coupling coefficientVSAvoidtransverse leakage

Core Design Contradiction:

Adaptability or versatilityVSObject-generated harmful factors

Solution Approach 1:

The multilayer electrode structure converts the potentially harmful transverse leakage into a controlled phenomenon. By carefully designing the density and thickness of the first layer, the device exploits the acoustic wave interactions to suppress transverse leakage while maintaining the beneficial electromechanical coupling of the low cut angle lithium niobate piezoelectric layer.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Reliability

If the first layer thickness is increased to suppress transverse leakage, then the quality factor is improved, but the device complexity increases

Engineering Contradiction:

Improvequality factorVSAvoidelectrode structure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The invention optimizes specific parameters of the multilayer electrode (density, thickness ratios, material composition) to achieve transverse leakage suppression and quality factor improvement. By carefully controlling these parameters within specific ranges, the device achieves enhanced performance without excessive complexity.

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 higher coupling factor and improved quality factor, reducing transverse leakage and enhancing the performance of the acoustic wave device, particularly in radio frequency applications.

Implementation Method 1

a piezoelectric layer configured such that a shear horizontal mode is a main mode of the acoustic wave device

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Implementation Method 2

an interdigital transducer electrode over the piezoelectric layer

Methodology Applied

Scientific EffectElectromechanical coupling: Piezoelectric Effect

Data Source

PatentUS12500570B2Shear horizontal mode acoustic wave device with multilayer interdigital transducer electrode

Publication Date: 2025.12.16 SKYWORKS SOLUTIONS INC

AI summary

An acoustic wave device is disclosed. The acoustic waved device can be a shear horizontal mode surface acoustic wave device. The acoustic wave device can include a piezoelectric layer, an interdigital transducer electrode over the piezoelectric layer, and a temperature compensation layer over the interdigital transducer electrode. The piezoelectric layer can be a lithium niobate layer with a cut angle in a range of −20° YX to 25° YX. The interdigital transducer electrode including a first layer and a second layer. The first layer affects acoustic properties of the acoustic wave device and the second layer affects electrical properties of the acoustic wave device. The second layer is positioned between the piezoelectric layer and the first layer such that a frequency response of the acoustic wave device includes a Rayleigh mode response at a frequency higher than a shear horizontal mode response.