Multilayer SAW Substrate Structure for Transverse Mode Suppression

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Solution Overview

Problem

Existing acoustic wave filters, particularly surface acoustic wave (SAW) devices, suffer from strong transverse modes that hinder accuracy and stability of oscillators and sensors, and degrade filter performance by creating passband ripples and limiting rejection.

Innovation Solution

Implementing a multilayer piezoelectric substrate SAW device with a border region having a different velocity from the central active region, featuring structures like multi-hammer head, notch, trench, or multi-thickness steps to suppress transverse modes without significantly degrading k2 or Q.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional SAW devices are used, then device simplicity is maintained, but transverse modes are strong causing passband ripples and degraded filter performance

Engineering Contradiction:

Improvefilter performanceVSAvoiddevice structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The device is segmented into a central active region and a border region with different acoustic velocities. This segmentation allows the border region to suppress transverse modes while the central region maintains strong electromechanical coupling, resolving the contradiction between filter performance and structural simplicity.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the device are given different acoustic velocity properties - the central active region has one velocity while the border region has a different velocity. This local differentiation enables transverse mode suppression at the borders without affecting the performance of the central region.

Inventive Principle:

Principle #3Local quality

2Manufacturing precision

If border region structures are added to suppress transverse modes, then passband ripples are reduced and rejection is improved, but device complexity increases

Engineering Contradiction:

Improvepassband flatnessVSAvoiddevice structure

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The solution extends the device structure in the lateral dimension by adding a border region surrounding the central active region. This dimensional extension provides a mechanism for suppressing transverse modes through velocity differentiation without compromising the central region's performance.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

3Reliability

If the border region velocity is made different from the central region, then transverse modes are suppressed, but manufacturing complexity increases

Engineering Contradiction:

Improvemode suppressionVSAvoiddevice fabrication

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The acoustic velocity parameter is changed in the border region compared to the central active region. This parameter change can be achieved through material selection or structural design, enabling transverse mode suppression while maintaining compatibility with existing manufacturing processes.

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

The proposed structures effectively suppress transverse modes, enhancing the accuracy and stability of SAW devices by reducing passband ripples and improving rejection, while maintaining high k2 and Q values.

Implementation Method 1

a piezoelectric layer over the support substrate

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Implementation Method 2

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 EffectSurface acoustic wave generation: Surface Acoustic Wave

Data Source

PatentUS20250330145A1Multilayer piezoelectric substrate surface acoustic wave device with transverse mode suppression

Publication Date: 2025.10.23 SKYWORKS SOLUTIONS INC

AI summary

A multilayer piezoelectric substrate acoustic wave device including an active region having a center region and a border region is disclosed. The acoustic wave device can include a support substrate, a piezoelectric layer over the support substrate, and an interdigital transducer electrode in electrical communication with the piezoelectric layer. The piezoelectric layer has a trench in the border region. The interdigital transducer electrode includes a bus bar and a finger extending from the bus bar. The finger in the border region has a first portion with a first width, a second portion with a second width between the center region and the first portion, and a third portion with a third width between the center region and the second portion. The second width is narrower than the first width and the third width.