Composite Piezoelectric Substrate Bonding for Crack-Resistant SAW Devices

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Existing composite substrates for surface acoustic wave devices face issues with temperature stability due to high thermal expansion coefficients, leading to crack generation and spurious noise, while using silicon as a support wafer for improved temperature characteristics is challenging.

Innovation Solution

A manufacturing method involving chemical or dry etching to remove damaged layers, followed by surface activation treatment and bonding with an intervening layer, and optionally ion implantation, to create a composite substrate with improved thermal shock resistance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If organic EL display devices use low-molecular-weight organic compounds, then device fabrication is simplified, but display quality deteriorates due to poor film-forming properties and short device lifetime

Engineering Contradiction:

Improvedevice fabricationVSAvoiddevice lifetime

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent changes the molecular weight parameter of organic compounds from low-molecular-weight to high-molecular-weight, which fundamentally alters the film-forming properties and device lifetime while maintaining ease of fabrication through solution processing

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent uses composite materials by combining high-molecular-weight organic compounds with specific solvents and additives to achieve both good film-forming properties and long device lifetime, resolving the contradiction between ease of manufacture and reliability

Inventive Principle:

Principle #40Composite materials

2Ease of manufacture

If organic EL display devices use low-molecular-weight organic compounds, then device fabrication is simplified, but display quality deteriorates due to poor film-forming properties

Engineering Contradiction:

Improvedevice fabricationVSAvoidfilm-forming properties

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The patent changes the molecular weight parameter from low to high, which directly improves film-forming properties while maintaining solution processability and ease of fabrication

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent applies local quality by optimizing the specific high-molecular-weight compound selection and solvent system to achieve uniform film formation in critical areas while maintaining overall fabrication simplicity

Inventive Principle:

Principle #3Local quality

3Productivity

If conventional solution is used to remove solvent from organic EL layer, then production time is reduced, but display quality deteriorates due to residual solvent affecting device lifetime

Engineering Contradiction:

Improveproduction timeVSAvoiddevice lifetime

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent introduces a specific solvent system as an intermediary that enables complete solvent removal during fabrication, eliminating residual solvent effects while maintaining efficient production timing

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent performs preliminary solvent selection and optimization before device fabrication, ensuring complete solvent removal capability is built into the process design, which prevents lifetime issues without adding production time

Inventive Principle:

Principle #10Preliminary action

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 method effectively suppresses crack generation and enhances temperature characteristics, maintaining filter performance and reducing spurious noise.

Implementation Method 1

where a damaged layer on a piezoelectric material substrate is removed by etching with an etching solution

Methodology Applied

Scientific EffectChemical etching:

Implementation Method 2

the piezoelectric material substrate and the support substrate are bonded to each other with an intervening layer in between

Methodology Applied

Scientific EffectBonding:

Implementation Method 3

ion implantation, to create a composite substrate with improved thermal shock resistance

Methodology Applied

Scientific EffectIon implantation: Ion Implantation

Data Source

PatentEP4144897B1Method for manufacturing composite substrate and composite substrate

Publication Date: 2025.08.20 SHIN ETSU CHEMICAL CO LTD

Figure 1~2
Figure 3
Figure 4

AI summary

A composite substrate capable of improving temperature characteristics while suppressing crack generation and a method for manufacturing such a composite substrate is provided. The method for manufacturing composite substrates in accordance with the present invention comprises: a step of preparing a piezoelectric material substrate having a rough surface; a step of removing the damaged layer by etching the rough surface of the piezoelectric material substrate using a chemical process; a step of depositing an intervening layer on the rough surface of the piezoelectric material substrate from which the damaged layer has been removed; a step of flattening the surface of the deposited intervening layer; a step of bonding the piezoelectric material substrate to a support substrate having a lower thermal expansion coefficient than the piezoelectric material, with the deposited intervening layer in between; and a step of thinning the piezoelectric material substrate after bonding. Lithium tantalate (LT) or lithium niobate (LN) are suitable as the piezoelectric material.