Integrated BAW Capacitor Layout for Spurious Mode Suppression

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Solution Overview

Problem

Existing bulk acoustic wave (BAW) resonators face challenges in achieving high quality factor (Q) and suppressing spurious modes while meeting filter specifications for steep skirts and low insertion loss, particularly in radio frequency applications.

Innovation Solution

Incorporating a metal-insulator-metal capacitor in parallel with the BAW resonator, utilizing an engineered piezoelectric layer with reduced piezoelectric coefficient and a frame structure to suppress spurious modes, and integrating the capacitor seamlessly with the resonator to reduce energy losses.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a conventional BAW resonator structure is used, then the device is simple to manufacture, but the quality factor is insufficient and spurious modes cannot be suppressed

Engineering Contradiction:

Improvequality factorVSAvoidresonator structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The resonator structure is segmented into distinct functional regions: an acoustically active region with piezoelectric layer for resonance, and frame regions with engineered low piezoelectric coefficient material for spurious mode suppression. This segmentation allows independent optimization of quality factor and spurious mode rejection.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the resonator are assigned different material properties: the acoustically active region uses high piezoelectric coefficient material for strong resonance, while the frame regions use engineered low piezoelectric coefficient material to suppress frame and transverse modes locally without affecting the main resonance.

Inventive Principle:

Principle #3Local quality

2Reliability

If the piezoelectric layer is extended to improve capacitor integration, then the capacitance increases, but spurious modes are enhanced

Engineering Contradiction:

ImprovecapacitanceVSAvoidspurious modes

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The piezoelectric layer is engineered with spatially varying properties: full piezoelectric coefficient in the acoustically active region for resonance, and reduced piezoelectric coefficient in the frame regions where the capacitor is integrated. This allows capacitance enhancement without exciting spurious frame modes.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The extended piezoelectric layer that would normally generate harmful spurious modes is converted into a beneficial capacitor structure by reducing the piezoelectric coefficient in the extension regions. The same structural extension provides both capacitance and spurious mode suppression.

Inventive Principle:

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

3Reliability

If separate capacitor and resonator structures are used, then the components are easy to manufacture independently, but energy losses increase and performance deteriorates

Engineering Contradiction:

Improveenergy efficiencyVSAvoidintegrated structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The capacitor and resonator are merged into a single integrated structure sharing common electrodes and substrate. The capacitor plates are formed using extensions of the resonator electrodes, eliminating the need for separate capacitor structures and reducing interconnect losses.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The piezoelectric layer serves multiple functions: it provides the piezoelectric effect for resonance in the acoustically active region, and simultaneously serves as the dielectric layer for the capacitor in the frame regions. This multi-functionality reduces the number of layers and improves energy efficiency.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 integrated capacitor structure enhances BAW resonator performance by maintaining high quality factor and improving skirt performance and insertion loss, while reducing frame and transverse modes, thus optimizing filter characteristics.

Implementation Method 1

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

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Implementation Method 2

a metal-insulator-metal capacitor in parallel with the bulk acoustic wave resonator

Methodology Applied

Scientific EffectCapacitance: Capacitance

Data Source

PatentUS20260005673A1Bulk acoustic wave device with capacitor

Publication Date: 2026.01.01 SKYWORKS GLOBAL PTE LTD

AI summary

Aspects of this disclosure relate to a bulk acoustic wave resonator and an integrated capacitor. In certain embodiments, the integrated capacitor can be a metal-insulator-metal capacitor in parallel with the bulk acoustic wave resonator. The metal-insulator-metal capacitor can include a portion of a first electrode and a portion of a second electrode of the bulk acoustic wave resonator. At least part of the metal-insulator-metal capacitor is positioned laterally relative to an acoustic reflector of the bulk acoustic wave resonator. Other embodiments of capacitors integrated with a bulk acoustic wave resonator are disclosed. Related filters, multiplexers, radio frequency modules, radio frequency systems, wireless communication devices, and methods are disclosed.