Multi-Layer Raised Frame for BAW Filters With Lower Insertion Loss

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Solution Overview

Problem

Existing bulk acoustic wave (BAW) filters face challenges in achieving low insertion loss and low Gamma loss, which are crucial for high-performance radio frequency electronic systems.

Innovation Solution

The implementation of a bulk acoustic wave device with a multi-layer raised frame structure, comprising a first raised frame layer with lower acoustic impedance and a second raised frame layer with higher density, positioned between electrodes and a piezoelectric layer, effectively blocks lateral energy leakage and moves the raised frame mode away from the main resonant frequency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If a raised frame structure is added to block lateral energy leakage, then insertion loss is reduced, but device complexity increases

Engineering Contradiction:

Improveinsertion lossVSAvoiddevice complexity

Core Design Contradiction:

Loss of energyVSDevice complexity

Solution Approach 1:

The raised frame structure is divided into multiple segments: a first raised frame layer (silicon dioxide) and a second raised frame layer (metal), each serving specific functions. This segmentation allows the structure to block lateral energy leakage effectively while managing acoustic impedance transitions, thereby reducing insertion loss without excessive complexity

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The raised frame structure uses composite materials combining silicon dioxide (first raised frame layer) and metal (second raised frame layer). This composite approach optimizes acoustic impedance matching and blocking characteristics, achieving low insertion loss by preventing lateral energy leakage into passive regions while maintaining a manageable structural complexity

Inventive Principle:

Principle #40Composite materials

2Loss of energy

If a raised frame structure is added to improve quality factor, then Gamma loss is reduced, but manufacturing precision requirements increase

Engineering Contradiction:

ImproveGamma lossVSAvoidmanufacturing precision

Core Design Contradiction:

Loss of energyVSManufacturing precision

Solution Approach 1:

The raised frame is segmented into two layers with distinct materials and positions. The first layer (silicon dioxide) provides acoustic isolation, while the second layer (metal) enhances mechanical support and acoustic blocking. This segmentation achieves high quality factor and low Gamma loss by effectively trapping acoustic energy, while the standardized layering approach facilitates manufacturing

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent specifies particular material parameters (silicon dioxide for the first layer, metal for the second layer) and their acoustic impedance characteristics. By controlling these material parameters and their arrangement, the structure achieves optimal acoustic energy confinement, improving quality factor and reducing Gamma loss with manufacturable precision requirements

Inventive Principle:

Principle #35Parameter changes

3Loss of energy

If the first raised frame layer with lower acoustic impedance is positioned between the piezoelectric layer and the first electrode, then lateral energy leakage is blocked, but the number of layers increases

Engineering Contradiction:

Improvelateral energy leakageVSAvoidnumber of layers

Core Design Contradiction:

Loss of energyVSDevice complexity

Solution Approach 1:

The first raised frame layer made of silicon dioxide acts as an intermediary layer between the piezoelectric layer and the first electrode. This intermediate structure provides acoustic impedance transition and blocking, effectively preventing lateral energy leakage into passive regions. The intermediary layer integrates seamlessly into the existing FBAR structure, adding minimal complexity while achieving effective energy confinement

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 configuration significantly reduces insertion loss and Gamma loss, enhancing the quality factor (Q) and reflection coefficient (Gamma) of the BAW filter, thereby improving the overall performance of the device.

Implementation Method 1

The first raised frame layer has a lower acoustic impedance than the first electrode

Methodology Applied

Scientific EffectAcoustic impedance: Acoustics

Implementation Method 2

The multi-layer raised frame structure can block lateral energy leakage from the active region to a passive region of the bulk acoustic wave device

Methodology Applied

Scientific EffectAcoustic energy blocking: Acoustics

Implementation Method 3

In BAW resonators, acoustic waves propagate in a bulk of a piezoelectric layer

Methodology Applied

Scientific EffectBulk acoustic wave propagation: Acoustics

Data Source

PatentUS12341486B2Multi-layer raised frame in bulk acoustic wave device

Publication Date: 2025.06.24 SKYWORKS GLOBAL PTE LTD

AI summary

Aspects of this disclosure relate to a bulk acoustic wave device that includes a multi-layer raised frame structure. The multi-layer raised frame structure includes a first raised frame layer positioned between a first electrode and a second electrode of the bulk acoustic wave device. The first raised frame layer has a lower acoustic impedance than the first electrode. The first raised frame layer and the second raised frame layer overlap in an active region of the bulk acoustic wave device. Related filters, multiplexers, packaged modules, wireless communication devices, and methods are disclosed.