Engineered Piezoelectric Regions in BAW Resonators for Spurious Mode Control

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Solution Overview

Problem

Existing bulk acoustic wave (BAW) devices face challenges in achieving high quality factor (Q), suppressing spurious modes, and improving heat dissipation while meeting performance specifications.

Innovation Solution

The BAW device incorporates engineered regions in the piezoelectric layer with reduced piezoelectric coefficients, including concentrically arranged cylindrical and ring-shaped structures, a frame structure, and engineered frame regions to suppress unwanted modes and enhance heat dissipation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the piezoelectric layer is made uniformly active across the entire device area, then the acoustic wave generation is maximized, but spurious modes and standing waves are generated that degrade performance

Engineering Contradiction:

Improvequality factorVSAvoidspurious modes

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The piezoelectric layer is divided into distinct regions with different piezoelectric coefficients. The first region has a higher piezoelectric coefficient for strong acoustic wave generation, while the second region has a lower piezoelectric coefficient to suppress spurious modes and standing waves. This local differentiation allows each region to perform its specific function optimally.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The piezoelectric layer is segmented into multiple functional zones: a first region for primary acoustic wave generation with high piezoelectric activity, and second regions for suppressing unwanted modes with reduced piezoelectric activity. This segmentation enables independent optimization of each region's contribution to overall device performance.

Inventive Principle:

Principle #1Segmentation

2Reliability

If the piezoelectric layer is made uniformly active across the entire device area, then the acoustic wave generation is maximized, but heat dissipation becomes insufficient leading to reduced heat durability

Engineering Contradiction:

Improvequality factorVSAvoidheat dissipation

Core Design Contradiction:

ReliabilityVSTemperature

Solution Approach 1:

Different regions of the piezoelectric layer are assigned different piezoelectric coefficients based on their functional requirements. The first region maintains high piezoelectric activity for acoustic wave generation, while the second region has reduced piezoelectric activity, which reduces heat generation and improves local heat dissipation capability.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The piezoelectric coefficient is changed spatially across the piezoelectric layer. By reducing the piezoelectric coefficient in specific second regions, the acoustic wave generation in those areas is reduced, which directly reduces the heat generated by piezoelectric heating effects, thereby improving heat dissipation and heat durability.

Inventive Principle:

Principle #35Parameter changes

3Power

If the piezoelectric layer uses high piezoelectric coefficient throughout, then acoustic wave generation is maximized, but energy losses increase due to spurious mode excitation

Engineering Contradiction:

Improveacoustic wave generationVSAvoidenergy losses

Core Design Contradiction:

PowerVSLoss of energy

Solution Approach 1:

The piezoelectric layer is divided into regions with different piezoelectric coefficients. The first region uses high piezoelectric coefficient material for strong acoustic wave generation, while the second region uses low piezoelectric coefficient material to prevent excitation of spurious modes, thereby reducing energy losses.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The invention converts what would normally be a harmful effect (spurious mode excitation and energy loss) into a beneficial outcome by strategically placing low piezoelectric coefficient regions at locations where spurious modes tend to form. This suppresses the harmful effects while preserving the desired acoustic wave generation in the first region.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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 engineered regions improve heat durability and reduce maximum temperature, enhancing the quality factor (Q) and reducing energy losses, while maintaining desired performance specifications.

Implementation Method 1

a piezoelectric layer positioned between the first electrode and the second electrode

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Data Source

PatentUS20260045928A1Bulk acoustic wave device with engineered regions

Publication Date: 2026.02.12 SKYWORKS GLOBAL PTE LTD

AI summary

Aspects of this disclosure relate to a bulk acoustic wave that includes a piezoelectric layer positioned between electrodes. The piezoelectric layer includes a first region and a plurality of second regions. The plurality of second regions each have an effective piezoelectric coefficient with a lower magnitude than an effective piezoelectric coefficient of the first region. Related acoustic wave filters, multiplexers, radio frequency modules, radio frequency systems, wireless communication devices, methods of manufacture, and methods of filtering are disclosed.