Stacked Piezoelectric BAW Resonator for Spurious Harmonic Suppression

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Solution Overview

Problem

Bulk acoustic wave resonators often produce spurious harmonic signals in addition to the main acoustic wave, which degrade their performance by introducing discontinuities into admittance curves, decreasing quality factor, and reducing acoustic coupling factor.

Innovation Solution

A bulk acoustic wave resonator is designed with a piezoelectric film comprising multiple layers of piezoelectric material, where at least one layer has a different dopant concentration than another layer, and the layers are arranged asymmetrically with respect to thickness or doping concentration to suppress spurious harmonic signals.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If a single-layer piezoelectric film is used, then the device structure is simple, but spurious harmonic signals are generated that degrade performance

Engineering Contradiction:

Improvepiezoelectric film structureVSAvoidperformance degradation from spurious signals

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The piezoelectric film is segmented into multiple layers with different doping concentrations. This segmentation allows each layer to contribute differently to the acoustic wave propagation, enabling suppression of spurious harmonic signals while maintaining the overall piezoelectric function of the film.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the piezoelectric film are given different doping concentrations to create local variations in acoustic velocity. The first region has a different doping concentration than the second region, creating local quality differences that manipulate acoustic wave behavior to suppress harmonics.

Inventive Principle:

Principle #3Local quality

2Reliability

If multiple layers with different doping concentrations are used, then spurious harmonic signals are suppressed, but the device complexity increases

Engineering Contradiction:

Improvesuppression of spurious harmonic signalsVSAvoidmulti-layer piezoelectric structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The doping concentration parameter is changed across different layers of the piezoelectric film. By varying this parameter spatially, the acoustic velocity is modified in different regions, enabling harmonic suppression without fundamentally changing the overall device architecture or requiring additional complex components.

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 asymmetric arrangement of differently doped piezoelectric layers effectively suppresses spurious harmonic signals, improving the frequency response and performance of bulk acoustic wave resonators by reducing unwanted acoustic waves.

Implementation Method 1

a piezoelectric film having multiple layers of piezoelectric material

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Data Source

PatentUS12244292B2Bulk acoustic wave resonator with stacked piezoelectric layers

Publication Date: 2025.03.04 SKYWORKS GLOBAL PTE LTD

AI summary

A bulk acoustic resonator comprises a membrane including a piezoelectric film having multiple layers of piezoelectric material. At least one of the multiple layers of piezoelectric material has a different dopant concentration than another of the multiple layers of piezoelectric material.