Multilayer Piezoelectric Substrate for Stable SAW Resonators

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Acoustic wave devices, such as SAW resonators, face challenges with temperature stability, mechanical robustness, and spurious signal suppression, particularly at high power levels and in radio frequency applications, due to materials with low thermal conductivity and fragility.

Innovation Solution

A multilayer piezoelectric substrate is developed, incorporating a layer of piezoelectric material bonded with a second material having lower thermal expansion, higher thermal conductivity, and greater toughness, such as silicon, which improves temperature stability and mechanical robustness, and includes features like roughened surfaces and obstacles to reduce spurious signals.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If a single layer of piezoelectric material is used, then the device structure is simple, but the temperature stability and mechanical robustness are poor

Engineering Contradiction:

Improvestructure simplicityVSAvoidtemperature stability

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The patent applies composite materials by bonding a piezoelectric material layer to a second material layer with lower thermal expansion coefficient and higher mechanical strength. This composite structure resolves the contradiction by maintaining structural simplicity while significantly improving temperature stability and reliability through the synergistic properties of the two materials.

Inventive Principle:

Principle #40Composite materials

2Ease of manufacture

If a single layer of piezoelectric material is used, then the manufacturing process is simple, but the mechanical robustness and power durability are insufficient

Engineering Contradiction:

Improvemanufacturing simplicityVSAvoidmechanical robustness

Core Design Contradiction:

Ease of manufactureVSStrength

Solution Approach 1:

The composite structure combines a piezoelectric material layer with a second material layer exhibiting superior mechanical properties. This approach maintains ease of manufacture through standard bonding processes while dramatically enhancing mechanical robustness and power durability, enabling the device to withstand high power levels and harsh operating conditions.

Inventive Principle:

Principle #40Composite materials

3Power

If a piezoelectric material with high piezoelectric coefficient is used, then the acoustic wave generation efficiency is high, but the thermal conductivity is low leading to poor temperature stability

Engineering Contradiction:

Improveacoustic wave generation efficiencyVSAvoidtemperature stability

Core Design Contradiction:

PowerVSTemperature

Solution Approach 1:

The patent resolves this contradiction by creating a composite structure where the piezoelectric material layer generates acoustic waves efficiently while the bonded second material layer with higher thermal conductivity dissipates heat effectively. This composite approach maintains high acoustic wave generation efficiency while achieving superior temperature stability through enhanced heat management.

Inventive Principle:

Principle #40Composite materials

4Ease of manufacture

If smooth surfaces are used at material interfaces, then the bonding is simple, but spurious signals are generated due to acoustic wave reflections

Engineering Contradiction:

Improvebonding simplicityVSAvoidspurious signals

Core Design Contradiction:

Ease of manufactureVSObject-generated harmful factors

Solution Approach 1:

The patent applies surface roughening to the material interfaces, creating a non-smooth, curved surface profile. This curvature/roughness approach resolves the contradiction by maintaining relatively simple bonding processes while effectively suppressing spurious signals through scattering and reducing acoustic wave reflections at the interfaces.

Inventive Principle:

Principle #14Spheroidality (Curvature)

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 enhances the reliability and power durability of SAW resonators by stabilizing operating parameters against temperature changes and reducing spurious signals, leading to improved performance and increased battery life in electronic devices.

Implementation Method 1

the second material has a lower coefficient of thermal expansion than the piezoelectric material

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Implementation Method 2

the second material has a higher thermal conductivity than the piezoelectric material

Methodology Applied

Scientific EffectThermal conductivity: Conduction (thermal)

Implementation Method 3

a layer of piezoelectric material having a lower surface bonded to an upper surface of a layer of a second material different from the piezoelectric material

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Data Source

PatentUS11750172B2Multilayer piezoelectric substrate

Publication Date: 2023.09.05 SKYWORKS SOLUTIONS INC

AI summary

A surface acoustic wave (SAW) resonator comprises a plurality of interdigital transducer electrodes disposed on a multilayer piezoelectric substrate (MPS) including a layer of piezoelectric material having a lower surface bonded to an upper surface of a layer of a second material different from the piezoelectric material that improves the temperature stability and reliability of the SAW resonator, and a layer of dielectric material disposed on an upper surface of the interdigital transducer electrodes and MPS.