BAW RF Filter Circuit Using AlScN Resonators Above 5 GHz

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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, such as aluminum nitride, grown on compatible crystalline substrates, with advanced transfer processes and structures to enhance the quality factor and electro-mechanical coupling for high-frequency bulk acoustic wave resonators, overcoming the limitations of polycrystalline film degradation.

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 fundamental material parameter from polycrystalline to single crystalline structure. This parameter change enables the resonators to maintain high quality factor at frequencies above 5 GHz by eliminating the thickness limitations that plague polycrystalline films, while the patent addresses manufacturing complexity through specialized growth and transfer processes

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent employs composite material structures by combining single crystalline piezoelectric thin films with compatible crystalline substrates. This composite approach allows the resonators to achieve superior acoustic performance at high frequencies while managing the complexity through integrated material systems designed for specific frequency ranges

Inventive Principle:

Principle #40Composite materials

2Reliability

If single crystalline or epitaxial piezoelectric thin films are used, then quality factor and electro-mechanical coupling improve for high-frequency operation, but manufacturing complexity and cost increase

Engineering Contradiction:

Improvequality factorVSAvoidmanufacturing process complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent applies preliminary action by pre-growing single crystalline or epitaxial piezoelectric thin films on compatible crystalline substrates before the resonator fabrication process. This preliminary crystal growth step ensures the material quality is established upfront, enabling high-frequency operation with improved quality factor while streamlining subsequent manufacturing steps

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent uses compatible crystalline substrates as intermediaries during the film growth process. These substrates serve as temporary carriers that facilitate the growth of high-quality single crystalline or epitaxial films, which can then be transferred to the final resonator structure, thereby managing manufacturing complexity through a controlled intermediate step

Inventive Principle:

Principle #24Intermediary (Mediator)

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 RF filters with improved performance and cost-efficiency, capable of operating at frequencies up to 5 GHz and beyond, meeting the demands of emerging data communication standards like 5G.

Implementation Method 1

bulk acoustic wave resonators using polycrystalline piezoelectric thin films

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Implementation Method 2

Acoustic wave resonator RF filter circuit

Methodology Applied

Scientific EffectPiezoelectric effect: Converse Piezoelectric Effect

Implementation Method 3

acoustic wave resonator

Methodology Applied

Scientific EffectResonance: Resonance

Data Source

PatentUS11646719B2Acoustic wave resonator RF filter circuit and system

Publication Date: 2023.05.09 AKOUSTIS TECHNOLOGIES CORP

AI summary

An RF filter system including a plurality of BAW resonators arranged in a circuit, the circuit including a serial configuration of resonators and a parallel shunt configuration of resonators, the circuit having a circuit response corresponding to the serial configuration and the parallel configuration of the plurality of bulk acoustic wave resonators including a transmission loss from a pass band having a bandwidth from 5.170 GHz to 5.835 GHz. Resonators include a support member with a multilayer reflector structure; a first electrode including tungsten; a piezoelectric film including aluminum scandium nitride; a second electrode including tungsten; and a passivation layer including silicon nitride. At least one resonator includes at least a portion of the first electrode located within a cavity region defined by a surface of the support member.