Multi-Layer SAW Filter Electrodes for Lower Side Leakage

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Solution Overview

Problem

Existing acoustic wave filters face challenges in reducing side leakage and mass loading in the gap region of interdigital transducer electrodes, which affects the performance and compactness of surface acoustic wave resonators.

Innovation Solution

The solution involves using a multi-layer interdigital transducer electrode with a first layer of a denser material and a second layer of a less dense material, where the thickness of the first layer in the gap region is smaller than in the center region, reducing mass loading and minimizing side leakage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If a uniform thickness interdigital transducer electrode is used, then the manufacturing process is simple, but mass loading in the gap region increases causing performance degradation

Engineering Contradiction:

Improveelectrode fabrication simplicityVSAvoidfilter performance

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent applies local quality by varying the thickness of the first electrode layer across different regions of the interdigital transducer. The first layer has a greater thickness in the center region than in the gap region, creating localized thickness variations that reduce mass loading in critical areas while maintaining overall structural integrity and electrical functionality.

Inventive Principle:

Principle #3Local quality

2Reliability

If a multi-layer electrode structure with varying thickness is used, then mass loading and side leakage are reduced, but the device complexity increases

Engineering Contradiction:

Improvefilter performanceVSAvoidelectrode structure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent employs composite materials by constructing the interdigital transducer electrode from multiple layers with different materials and thicknesses. The first electrode layer uses a denser material with greater thickness in the center region, while the second electrode layer uses a less dense material with greater thickness in the gap region, creating a composite structure that optimizes both acoustic performance and electrical properties.

Inventive Principle:

Principle #40Composite materials

3Object-generated harmful factors

If the first layer thickness in gap region is reduced, then side leakage is minimized, but the electrical properties may be impacted

Engineering Contradiction:

Improveside leakageVSAvoidelectrical properties

Core Design Contradiction:

Object-generated harmful factorsVSReliability

Solution Approach 1:

The patent resolves the conflict between reducing side leakage and maintaining electrical properties by using a composite two-layer electrode structure. The first layer with denser material has reduced thickness in the gap region to minimize side leakage, while the second layer with less dense material has increased thickness in the gap region to compensate and maintain proper electrical properties, achieving both goals simultaneously.

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 enhances the performance of acoustic wave filters by reducing mass loading and side leakage, allowing for more compact and efficient designs without significantly impacting electrical properties.

Implementation Method 1

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 on which the interdigital transductor electrode is disposed.

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Implementation Method 2

An interdigital transducer electrode is disposed over the piezoelectric layer, the interdigital transducer electrode being thicker in a center region of the interdigital transducer electrode than in a gap region of the interdigital transducer electrode to thereby reduce a mass loading of the interdigital transducer electrode in the gap region.

Methodology Applied

Scientific EffectMass loading reduction:

Data Source

PatentUS12368431B2Acoustic wave filter with multiple acoustic wave devices on a subtrate

Publication Date: 2025.07.22 SKYWORKS SOLUTIONS INC

AI summary

An acoustic wave filter includes a piezoelectric layer. A first acoustic wave device includes a portion of the piezoelectric layer and a first multi-layer interdigital transducer electrode disposed over the first portion of the piezoelectric layer. Additional acoustic wave devices are coupled to the first acoustic wave device, the additional acoustic wave devices including a second portion of the piezoelectric layer and a plurality of multi-layer interdigital transducer electrodes disposed over the second portion of the piezoelectric layer. At least one of the plurality of multi-layer interdigital transducer electrodes includes a layer that is thinner than a corresponding layer of the same material of the first multi-layer interdigital transducer electrode of the first acoustic wave device.