Ceramic Multilayer SAW Substrate for Spurious Mode Suppression

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Acoustic wave devices, particularly those with polycrystalline spinel substrates, face issues with spurious responses due to back reflections from high impedance support substrates, leading to degraded frequency response and performance.

Innovation Solution

Incorporating a polycrystalline spinel layer as a ceramic substrate with a single crystal support substrate and a piezoelectric layer, which scatters back reflections and enhances thermal dissipation, using direct bonding without intervening adhesives to improve structural integrity and reduce spurious modes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If a high impedance support substrate is used, then the acoustic wave device can be manufactured, but spurious responses occur due to back reflections leading to degraded frequency response

Engineering Contradiction:

ImprovemanufacturabilityVSAvoidfrequency response

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent converts the harmful back reflections from the support substrate into beneficial scattering of spurious modes. By introducing a ceramic layer with specific acoustic impedance between the piezoelectric layer and the high impedance support substrate, the structure transforms the problematic reflections into useful scattering that suppresses spurious responses while maintaining manufacturability

Inventive Principle:

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

Solution Approach 2:

The patent introduces a ceramic layer as an intermediary between the piezoelectric layer and the support substrate. This intermediate layer with controlled acoustic impedance acts as a mediator that prevents direct interaction between the acoustic wave and the high impedance support substrate, thereby eliminating back reflections while preserving the structural support function

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If the piezoelectric layer is made thicker to improve performance, then the acoustic wave generation is enhanced, but the chip temperature increases due to reduced thermal dissipation

Engineering Contradiction:

Improveacoustic wave generationVSAvoidchip temperature

Core Design Contradiction:

ReliabilityVSTemperature

Solution Approach 1:

The patent employs a composite structure consisting of the piezoelectric layer, ceramic layer, and support substrate with different thermal and acoustic properties. This composite material approach allows the thick piezoelectric layer to generate strong acoustic waves while the ceramic layer and support substrate provide enhanced thermal dissipation pathways, preventing excessive temperature rise

Inventive Principle:

Principle #40Composite materials

3Ease of manufacture

If adhesive layers are used to bond the ceramic layer to the support substrate, then the bonding is easier to achieve, but the structural integrity is reduced and spurious modes are generated

Engineering Contradiction:

Improvebonding processVSAvoidstructural integrity

Core Design Contradiction:

Ease of manufactureVSStrength

Solution Approach 1:

The patent removes the adhesive layer from the structure, achieving direct bonding between the ceramic layer and the support substrate. This extraction of the adhesive intermediary eliminates the source of spurious modes generated at adhesive interfaces while maintaining strong structural integrity through direct material contact

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent enables the ceramic layer and support substrate to bond directly to each other without requiring an adhesive intermediary. The surfaces of these layers are prepared to facilitate self-bonding through direct contact, achieving both strong structural integrity and elimination of adhesive-related spurious modes

Inventive Principle:

Principle #25Self-service

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 suppresses spurious modes and improves thermal dissipation, maintaining frequency stability and reducing chip temperature, thereby enhancing the performance of acoustic wave devices.

Implementation Method 1

the ceramic layer is arranged to scatter back reflections of the acoustic wave

Methodology Applied

Scientific EffectScattering: Scattering

Implementation Method 2

The support substrate has a higher thermal conductivity than the ceramic layer

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Implementation Method 3

A surface acoustic wave resonator can include an interdigital transductor electrode on a piezoelectric substrate. The surface acoustic wave resonator can generate a surface acoustic wave on a surface of the piezoelectric layer

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Data Source

PatentUS12500568B2Acoustic wave device with multi-layer substrate including ceramic

Publication Date: 2025.12.16 SKYWORKS SOLUTIONS INC

AI summary

An acoustic wave device is disclosed. The acoustic wave device includes a support layer, a ceramic layer positioned over the support layer, a piezoelectric layer positioned over the ceramic layer, and an interdigital transducer electrode positioned over the piezoelectric layer. The support layer has a higher thermal conductivity than the ceramic layer. The ceramic layer can be a polycrystalline spinel layer. The acoustic wave device can be a surface acoustic wave device configured to generate a surface acoustic wave.