Acoustic Wave Layer Structure for Lower Insertion Loss and IMD

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Solution Overview

Problem

Acoustic wave devices with bonding layers suffer from increased insertion loss and degraded intermodulation distortion (IMD) characteristics due to conductance effects and stray electron generation.

Innovation Solution

Incorporating a low-resistivity layer with Al as a main component, positioned closer to the piezoelectric layer than the bonding layer, to reduce insertion loss and improve IMD by minimizing the effect of conductance and stray electron interference.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If a bonding layer is provided between low-acoustic-velocity films, then the multilayer substrate can be formed by bonding, but the Q value is degraded due to conductance effects and insertion loss increases

Engineering Contradiction:

Improvebonding capabilityVSAvoidinsertion loss

Core Design Contradiction:

Ease of manufactureVSLoss of energy

Solution Approach 1:

A low-resistivity layer is introduced as an intermediary between the bonding layer and the piezoelectric layer. This low-resistivity layer acts as a mediator to suppress conductance effects while maintaining the bonding function of the bonding layer, thereby reducing insertion loss without compromising manufacturing capability.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The structure is segmented by dividing the functional layers into distinct components: the bonding layer for manufacturing purposes and the low-resistivity layer for electrical performance. This segmentation allows each layer to perform its specific function optimally without interfering with the other.

Inventive Principle:

Principle #1Segmentation

2Ease of manufacture

If the bonding layer contacts the low-acoustic-velocity films, then the multilayer structure is formed, but stray electrons are easily generated and IMD characteristics are degraded

Engineering Contradiction:

Improvestructure formationVSAvoidstray electron generation

Core Design Contradiction:

Ease of manufactureVSObject-generated harmful factors

Solution Approach 1:

The low-resistivity layer serves as an intermediary barrier between the bonding layer and the low-acoustic-velocity films. This intermediary layer prevents direct contact that would generate stray electrons, while still allowing the bonding layer to perform its structural function.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The low-resistivity layer, which has inherently low resistance, is strategically positioned to convert potential harmful conductance effects into a beneficial shielding effect that traps and dissipates stray electrons before they can interfere with the piezoelectric layer and degrade IMD characteristics.

Inventive Principle:

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

3Loss of energy

If the low-resistivity layer is positioned closer to the piezoelectric layer than the bonding layer, then conductance effects are reduced and insertion loss decreases, but the layer structure becomes more complex

Engineering Contradiction:

Improveinsertion lossVSAvoidlayer structure

Core Design Contradiction:

Loss of energyVSDevice complexity

Solution Approach 1:

The low-resistivity layer is strategically positioned only in the region where it is most needed - closer to the piezoelectric layer than the bonding layer. This local placement optimizes the suppression of conductance effects and stray electron generation at the critical interface, while minimizing the overall structural complexity.

Inventive Principle:

Principle #3Local quality

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 effectively reduces or prevents the increase in insertion loss and enhances IMD performance by ensuring the low-resistivity layer's resistivity is lower than the bonding layer's, thereby reducing conductance effects and trapping stray electrons.

Implementation Method 1

a low-resistivity layer between the support substrate and the piezoelectric layer... A resistivity of the low-resistivity layer is lower than a resistivity of the bonding layer

Methodology Applied

Scientific EffectElectrical Resistance: Electrical Resistance

Implementation Method 2

when the bonding layer contacts the low-acoustic-velocity films stray electrons are easily generated... The low-resistivity layer is closer to the piezoelectric layer than the bonding layer... trapping stray electrons

Methodology Applied

Scientific EffectElectron trapping: Gettering

Implementation Method 3

a piezoelectric layer on the intermediate layer... An interdigital transducer (IDT) electrode is provided on the piezoelectric film

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Implementation Method 4

acoustic wave device includes a multilayer substrate including a high-acoustic-velocity support substrate, low-acoustic-velocity films, and a piezoelectric film

Methodology Applied

Scientific EffectSurface acoustic wave: Surface Acoustic Wave

Data Source

PatentUS20240048116A1Acoustic wave device

Publication Date: 2024.02.08 MURATA MFG CO LTD

AI summary

An acoustic wave device includes a support substrate, an intermediate layer on the support substrate, a piezoelectric layer on the intermediate layer, a bonding layer between the support substrate and the piezoelectric layer, a low-resistivity layer between the support substrate and the piezoelectric layer, and an IDT electrode on the piezoelectric layer and including a pair of busbars and first and second electrode fingers. The low-resistivity layer closer to the piezoelectric layer than the bonding layer and includes Al as a main component.