Patterned BAW Resonator Layers for Spurious Mode Suppression

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Solution Overview

Problem

Bulk Acoustic Wave (BAW) resonators face performance issues at higher 5G frequencies due to scaling problems and significant increases in acoustic losses, limiting their effectiveness in filters and oscillators.

Innovation Solution

The development of bulk acoustic wave resonator structures with a piezoelectric resonant volume comprising alternating axis piezoelectric layers and multilayer metal acoustic reflector electrodes, including current spreading layers, to enhance acoustic isolation and reduce losses, allowing operation at higher frequencies.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If conventional BAW resonator structures are used, then fabrication is simpler, but acoustic losses increase significantly at higher 5G frequencies

Engineering Contradiction:

Improveacoustic lossesVSAvoidresonator structure complexity

Core Design Contradiction:

Loss of energyVSDevice complexity

Solution Approach 1:

The resonator is divided into multiple functional layers including piezoelectric layers, acoustic reflector layers, and current spreading layers. Each layer serves a specific function in reducing acoustic losses or managing electrical currents, thereby addressing the acoustic loss problem without creating a monolithic complex structure.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent employs composite material structures combining piezoelectric materials with acoustic reflector materials of different acoustic impedances. This composite approach creates acoustic isolation that reduces energy loss at interfaces while maintaining overall structural integrity and manageable complexity.

Inventive Principle:

Principle #40Composite materials

2Speed

If BAW resonators are scaled for higher frequencies, then operating frequency increases, but acoustic losses increase significantly

Engineering Contradiction:

Improveoperating frequencyVSAvoidacoustic losses

Core Design Contradiction:

SpeedVSLoss of energy

Solution Approach 1:

Acoustic reflector layers are strategically positioned at specific locations within the resonator structure where acoustic energy loss occurs. These localized interventions target high-loss regions without requiring a complete redesign of the entire resonator, enabling high-frequency operation with reduced losses.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

Acoustic reflector layers act as intermediary structures between different piezoelectric layers, preventing acoustic energy from leaking into adjacent layers. This mediation reduces acoustic losses and enables the resonator to operate at higher frequencies with improved efficiency.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Reliability

If acoustic isolation is increased through multilayer structures, then quality factor improves, but device complexity increases

Engineering Contradiction:

Improvequality factorVSAvoidlayer structure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

Multiple layers are merged into an integrated resonator structure where acoustic reflector layers, piezoelectric layers, and current spreading layers work together as a unified system. This merging achieves improved quality factor through enhanced acoustic isolation while managing complexity through integrated design.

Inventive Principle:

Principle #5Merging (Combining)

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 design improves the quality factor of bulk acoustic wave resonators, enabling better performance at higher frequencies by reducing acoustic absorption and increasing acoustic isolation, thus addressing the scaling and loss issues in BAW resonators.

Implementation Method 1

a piezoelectric resonant volume comprising alternating axis piezoelectric layers

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Implementation Method 2

multilayer metal acoustic reflector electrodes, including current spreading layers, to enhance acoustic isolation

Methodology Applied

Scientific EffectAcoustic reflection: Reflection

Implementation Method 3

piezoelectric resonant volume comprising alternating axis piezoelectric layers

Methodology Applied

Scientific EffectBulk acoustic wave generation: Resonance

Data Source

PatentUS20230216476A1Bulk acoustic wave (BAW) resonator, patterned layer structures, devices and systems

Publication Date: 2023.07.06 QXONIX INC

AI summary

Techniques for improving Bulk Acoustic Wave (BAW) reflector and resonator structures are disclosed, including filters, oscillators and systems that may include such devices. A Bulk Acoustic Wave (BAW) resonator of this disclosure may comprise a substrate and an active piezoelectric resonant volume. The active piezoelectric resonant volume of the Bulk Acoustic Wave (BAW) resonator may have a main resonant frequency. The active piezoelectric resonant volume of the Bulk Acoustic Wave (BAW) resonator may comprise first and second piezoelectric layers having respective piezoelectric axis that substantially oppose one another. A first patterned layer may be disposed within the active piezoelectric volume. This may, but need not facilitate suppression of spurious modes. The main resonant frequency of the Bulk Acoustic Wave (BAW) resonator may be in a super high frequency (SHF) band. The main resonant frequency of the Bulk Acoustic Wave (BAW) resonator may be in an extremely high frequency (EHF) band.