Multi-Layer Piezoelectric Substrate for Boundary Wave Confinement

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Solution Overview

Problem

Boundary acoustic wave devices face challenges in confining acoustic waves and achieving thin device thickness, which affects their size and efficiency in radio frequency applications.

Innovation Solution

A multi-layer piezoelectric device with high velocity layers on opposing sides of a piezoelectric layer and a low velocity layer between them, generating a boundary acoustic wave that is concentrated at the interface, improving wave confinement and allowing for a thinner device structure.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If boundary acoustic wave devices are designed to confine acoustic waves, then acoustic energy concentration is improved, but device thickness increases

Engineering Contradiction:

Improveacoustic wave confinementVSAvoiddevice thickness

Core Design Contradiction:

ReliabilityVSLength of moving object

Solution Approach 1:

The device is segmented into multiple functional layers: piezoelectric layer, low acoustic velocity layer, and high acoustic velocity layers. This segmentation allows each layer to perform a specific function in confining acoustic waves, achieving effective confinement without requiring excessive overall thickness.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different layers are assigned different acoustic velocity properties: the low acoustic velocity layer (silicon dioxide) is positioned where acoustic energy concentration is needed, while high acoustic velocity layers (silicon) are positioned to reflect and confine waves. This local differentiation of material properties enables precise control of acoustic wave behavior at specific locations within the thin device structure.

Inventive Principle:

Principle #3Local quality

2Volume of moving object

If device thickness is reduced for compactness, then device size is improved, but acoustic wave confinement capability deteriorates

Engineering Contradiction:

Improvedevice sizeVSAvoidacoustic wave confinement

Core Design Contradiction:

Volume of moving objectVSReliability

Solution Approach 1:

The device employs a composite structure combining materials with different acoustic velocities: silicon dioxide (low velocity) and silicon (high velocity). This composite material approach enables effective acoustic wave confinement within a compact thickness by utilizing the contrasting acoustic properties of the different materials to trap and guide acoustic energy.

Inventive Principle:

Principle #40Composite materials

3Reliability

If high velocity layers are added to improve wave confinement, then acoustic energy concentration is improved, but device complexity increases

Engineering Contradiction:

Improveacoustic energy concentrationVSAvoidlayer structure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The high acoustic velocity silicon layers serve multiple functions: they act as acoustic wave reflectors to confine energy, provide mechanical support for the thin-film structure, and serve as electrical contact layers for the piezoelectric device. This multi-functionality reduces the need for additional separate components, thereby limiting the increase in device complexity.

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 solution effectively confines acoustic energy within the device, enabling a compact and efficient radio frequency module with improved temperature compensation and electromechanical coupling, reducing the overall size and radiation loss.

Implementation Method 1

an interdigital transducer electrode on the piezoelectric layer

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Implementation Method 2

high velocity layers on opposing sides of the piezoelectric layer and a low velocity layer positioned between the piezoelectric layer and a first high velocity layer... acoustic energy is concentrated at a boundary of the piezoelectric layer and the low velocity layer

Methodology Applied

Scientific EffectAcoustic wave confinement: Total Internal Reflection

Data Source

PatentUS11689178B2Acoustic wave device with multi-layer piezoelectric substrate

Publication Date: 2023.06.27 SKYWORKS SOLUTIONS INC

AI summary

Aspects of this disclosure relate to an acoustic wave device that includes high velocity layers on opposing sides of a piezoelectric layer. A low velocity layer can be positioned between the piezoelectric layer and one of the high velocity layers, in which the low velocity layer has a lower acoustic velocity than the high velocity layers. The acoustic wave device can be configured to generate a boundary acoustic wave such that acoustic energy is concentrated at a boundary of the piezoelectric layer and the low velocity layer.