IDT Electrode Material Layout for Lower IMD in Acoustic Wave Filters

Solution Overview

Problem

Existing acoustic wave devices face challenges in sufficiently suppressing intermodulation distortion (IMD), which affects their filter characteristics.

Innovation Solution

The acoustic wave device incorporates a piezoelectric substrate with an interdigital transducer (IDT) electrode featuring a combination of two metals with different densities and Young's moduli, where the second metal has a higher density and Young's modulus, strategically placed in regions facing gaps between electrode fingers to reduce distortion.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If a uniform Al-Cu alloy IDT electrode is used, then the manufacturing process is simple, but intermodulation distortion (IMD) cannot be sufficiently suppressed

Engineering Contradiction:

Improvemanufacturing simplicityVSAvoidintermodulation distortion

Core Design Contradiction:

Ease of manufactureVSObject-affected harmful factors

Solution Approach 1:

The IDT electrode is divided into multiple regions along the acoustic wave propagation direction, with each region having a different metal composition ratio. Specifically, the electrode includes a first region with a first Al-Cu alloy ratio, a second region with a second Al-Cu alloy ratio, and optionally a third region with a third Al-Cu alloy ratio. This local variation in material composition allows different sections to contribute differently to suppressing intermodulation distortion while maintaining manufacturing feasibility through a systematic gradient structure.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The IDT electrode employs composite Al-Cu alloy materials with varying composition ratios across different regions. The electrode combines aluminum and copper in different proportions to create regions with distinct acoustic and electrical properties. This composite material approach enables the electrode to suppress intermodulation distortion by creating acoustic impedance variations that interfere with distortion signal generation, while still being manufacturable using standard alloy deposition techniques.

Inventive Principle:

Principle #40Composite materials

2Device complexity

If the IDT electrode is made of a single material, then the structure is simple, but filter characteristics cannot be sufficiently improved

Engineering Contradiction:

Improveelectrode structure complexityVSAvoidfilter characteristic performance

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The IDT electrode is divided into multiple regions along the acoustic wave propagation direction, with each region having a different metal composition ratio. Specifically, the electrode includes a first region with a first Al-Cu alloy ratio, a second region with a second Al-Cu alloy ratio, and optionally a third region with a third Al-Cu alloy ratio. This local variation in material composition allows different sections to contribute differently to suppressing intermodulation distortion while maintaining manufacturing feasibility through a systematic gradient structure.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The IDT electrode employs composite Al-Cu alloy materials with varying composition ratios across different regions. The electrode combines aluminum and copper in different proportions to create regions with distinct acoustic and electrical properties. This composite material approach enables the electrode to suppress intermodulation distortion by creating acoustic impedance variations that interfere with distortion signal generation, while still being manufacturable using standard alloy deposition techniques.

Inventive Principle:

Principle #40Composite materials

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 effectively reduces or prevents intermodulation distortion, enhancing the filter characteristics of the acoustic wave device.

Implementation Method 1

a piezoelectric substrate and an IDT electrode on the piezoelectric substrate

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Implementation Method 2

an interdigital transducer (IDT) electrode is provided on a LiTaO3 substrate

Methodology Applied

Scientific EffectSurface acoustic wave generation: Surface Acoustic Wave

Data Source

PatentUS11811388B2Acoustic wave device

Publication Date: 2023.11.07 MURATA MFG CO LTD

AI summary

An acoustic wave device includes a piezoelectric substrate and an IDT electrode on the piezoelectric substrate. The IDT electrode includes a first comb-shaped electrode including first electrode fingers and a second comb-shaped electrode including second electrode fingers. The IDT electrode includes a first portion in which a main electrode layer includes a first metal and a second portion in which a main electrode layer includes a second metal. The first electrode fingers and the second comb-shaped electrode include first facing portions facing each other with a gap in between, and the second electrode fingers and the first comb-shaped electrode include second facing portions facing each other with a gap in between. At least one of the first facing portions and second facing portions is the second portion, and a portion of the IDT electrode other than the second portion is the first portion.