Elastic Wave Device Wiring Integrity via Dielectric Layer Angles

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Solution Overview

Problem

Existing band pass filters with surface acoustic wave elements on piezoelectric substrates face issues due to height differences between IDT electrodes, leading to potential breaks in wiring electrodes.

Innovation Solution

The design includes a piezoelectric substrate with a first and second IDT electrode separated by an elevation portion, where the second dielectric layer extends over the second IDT electrode, and the angles between the dielectric layer's side surfaces and the substrate's surface are smaller than those of the first dielectric layer, reducing the likelihood of wiring electrode breaks.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If the second IDT electrode is provided directly over the first IDT electrode without an insulative material layer, then the device structure is simplified, but the upper surfaces of the IDT electrodes have different heights causing elevation portions that may break wiring electrodes

Engineering Contradiction:

Improvedevice structureVSAvoidwiring electrode integrity

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

A second dielectric layer is introduced as an intermediary component between the first and second IDT electrodes. This layer fills the elevation portion created by the height difference and provides a flat upper surface for the wiring electrode, preventing breaks while maintaining the simplified direct-overlapping structure

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The second dielectric layer extends in the vertical dimension to fill the elevation portion and create a flat upper surface. By adding this vertical dimension solution, the wiring electrode can be laid flat without following the uneven terrain of the IDT electrode height differences

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Reliability

If the wiring electrode extends over the elevation portion to connect the IDT electrodes, then electrical connection is achieved, but the wiring electrode may break due to the elevation portion

Engineering Contradiction:

Improveelectrical connectionVSAvoidwiring electrode strength

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The second dielectric layer acts as a mediator that eliminates the elevation portion. By filling the height difference and providing a flat surface, it allows the wiring electrode to maintain full strength without being compromised by spanning over an elevation

Inventive Principle:

Principle #24Intermediary (Mediator)

3Reliability

If the angles between the second dielectric layer side surfaces and the substrate surface are smaller than those of the first dielectric layer, then wiring electrode breaks are prevented, but the dielectric layer thickness must be adjusted

Engineering Contradiction:

Improvewiring electrode integrityVSAvoiddielectric layer thickness control

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The angles of the second dielectric layer side surfaces are controlled to be smaller than those of the first dielectric layer. This parameter change in the geometric configuration prevents wiring electrode breaks by creating a more gradual transition, while the thickness is adjusted accordingly to maintain the flat upper surface

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

This configuration minimizes the occurrence of wiring electrode breaks and allows for adjustment of frequency band width and temperature characteristics by varying the dielectric layer thickness, enhancing the reliability and performance of elastic wave devices.

Implementation Method 1

a piezoelectric substrate that includes a principal surface; a first interdigital transducer (IDT) electrode that is provided over the principal surface of the piezoelectric substrate

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Data Source

PatentUS11387807B2Elastic wave device, high-frequency front end circuit, and communication device

Publication Date: 2022.07.12 MURATA MFG CO LTD

AI summary

An elastic wave device includes first and second IDT electrodes provided over a principal surface of a piezoelectric substrate. The first IDT electrode is provided directly on a principal surface of the piezoelectric substrate and the second IDT electrode is provided over the principal surface with a first dielectric layer interposed therebetween. A second dielectric layer extends to upper portions of the first and second IDT electrodes. A wiring electrode passes over the second dielectric layer and extends to the upper portions of the first and second IDT electrodes. Respective angles between first and second side surfaces of the second dielectric layer and the principal surface of the piezoelectric substrate are smaller than an angle between a side surface of the first dielectric layer and the principal surface of the piezoelectric substrate.