BAW Resonator Filter Layout for High-Q Rejection-Band Isolation

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Solution Overview

Problem

Current bulk acoustic wave resonators using polycrystalline piezoelectric thin films face degradation in quality at frequencies above 5 GHz due to thickness limitations, necessitating the development of high-quality single crystalline or epitaxial piezoelectric thin films for improved performance in RF filters.

Innovation Solution

The use of single crystalline or epitaxial piezoelectric thin films grown on compatible substrates, combined with advanced manufacturing processes such as thin film transfer and energy confinement structures, to enhance the quality factor and electro-mechanical coupling of bulk acoustic wave resonators for high-frequency applications.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If polycrystalline piezoelectric thin films are used in bulk acoustic wave resonators, then manufacturing is easier and cost is lower, but quality factor degrades at frequencies above 5 GHz due to thickness limitations

Engineering Contradiction:

Improvequality factorVSAvoidmanufacturing complexity

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent changes the material parameter from polycrystalline to single crystalline piezoelectric thin films, which fundamentally alters the quality factor characteristics at high frequencies while maintaining compatibility with existing thin film fabrication processes

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent employs composite material structures by integrating single crystalline piezoelectric layers with compatible substrate materials and electrode structures, optimizing both performance and manufacturability

Inventive Principle:

Principle #40Composite materials

2Reliability

If single crystalline or epitaxial piezoelectric thin films are used to improve quality factor at high frequencies, then performance above 5 GHz is enhanced, but manufacturing process complexity increases

Engineering Contradiction:

Improvequality factorVSAvoidmanufacturing process complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent uses compatible substrate materials as intermediaries to grow single crystalline or epitaxial piezoelectric thin films, enabling high-quality film formation through controlled crystal growth processes while maintaining manufacturing feasibility

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent performs preliminary substrate preparation and crystal orientation alignment before thin film deposition, ensuring that single crystalline or epitaxial films grow with proper orientation for optimal piezoelectric performance at high frequencies

Inventive Principle:

Principle #10Preliminary action

3Reliability

If thin film thickness is increased to maintain quality at higher frequencies using polycrystalline films, then manufacturing remains simple, but insertion loss increases and performance degrades

Engineering Contradiction:

Improveinsertion lossVSAvoidthin film thickness

Core Design Contradiction:

ReliabilityVSLength of stationary object

Solution Approach 1:

The patent changes the crystalline structure parameter from polycrystalline to single crystalline or epitaxial, which improves the quality factor and reduces insertion loss, allowing for optimized thin film thickness at high frequencies without the degradation associated with thicker polycrystalline films

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

This approach enables the production of high-quality bulk acoustic wave resonators with improved performance and cost-efficiency, capable of meeting the demands of contemporary data communication systems, particularly in 5.2 GHz Wi-Fi applications, by maintaining high Q factors and low insertion loss across a wide frequency range.

Implementation Method 1

bulk acoustic wave resonators using polycrystalline piezoelectric thin films

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Implementation Method 2

single crystalline or epitaxial piezoelectric thin films grown on compatible substrates

Methodology Applied

Scientific EffectEpitaxy: Epitaxy

Data Source

PatentUS11838005B2Bulk acoustic wave resonator filters including rejection-band resonators

Publication Date: 2023.12.05 AKOUSTIS TECHNOLOGIES CORP

AI summary

A BAW resonator filter can include a BAW resonator pass-band filter ladder, the BAW resonator pass-band filter ladder can be configured to pass frequency components of an input signal in a pass-band of frequencies received at an input node of the BAW resonator pass-band filter ladder to an output node of the BAW resonator pass-band filter ladder. A first rejection-band series resonator can be coupled in series between an input port of the BAW resonator pass-band filter ladder and the input node, the first rejection-band series resonator can have a first anti-resonant frequency peak in a rejection-band of frequencies that is less than the pass-band of frequencies. A second rejection-band series resonator can be coupled in series between an output port of the BAW resonator filter and the output node, the second rejection-band series resonator can have a second anti-resonant frequency peak in the rejection-band of frequencies.