Guided Wave Piezoelectric Layer Thinning for Frequency Tuning

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Solution Overview

Problem

Existing MEMS guided wave devices face challenges in manufacturing efficiency and utility due to limitations in accessing exposed portions of piezoelectric layers, difficulty in adjusting properties like frequency and coupling coefficient, and integration of functional structures without interfering with electrodes such as IDTs.

Innovation Solution

A MEMS guided wave device design where electrodes are arranged below the piezoelectric layer, allowing for transduction of lateral acoustic waves, with a slow wave propagation layer and guided wave confinement structures to confine the waves, enabling adjustments and additions to the piezoelectric layer for enhanced utility.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If electrodes are arranged above the piezoelectric layer (conventional IDT configuration), then transduction of lateral acoustic waves is achieved, but access to exposed portions of the piezoelectric layer is limited and manufacturing efficiency is reduced

Engineering Contradiction:

Improvemanufacturing efficiencyVSAvoidaccess difficulty to piezoelectric layer

Core Design Contradiction:

Ease of manufactureVSDevice complexity

Solution Approach 1:

The patent inverts the conventional electrode arrangement by placing electrodes below the piezoelectric layer rather than above it. This inversion allows the top surface of the piezoelectric layer to remain exposed and accessible for additional functional structures, while still achieving effective transduction of lateral acoustic waves through the piezoelectric material.

Inventive Principle:

Principle #13The other way round (Inversion)

2Power

If the piezoelectric layer thickness is increased, then power handling capability is improved, but frequency adjustment flexibility is reduced

Engineering Contradiction:

Improvepower handling capabilityVSAvoidfrequency adjustment flexibility

Core Design Contradiction:

PowerVSAdaptability or versatility

Solution Approach 1:

The patent applies local quality by creating regions of different piezoelectric layer thicknesses within the same device structure. Some regions have thicker piezoelectric layers for enhanced power handling, while other regions have thinner layers for frequency tuning and adjustment, allowing both requirements to be satisfied simultaneously in different spatial locations.

Inventive Principle:

Principle #3Local quality

3Adaptability or versatility

If functional structures are integrated into the piezoelectric layer, then device utility is enhanced, but interference with electrodes such as IDTs occurs

Engineering Contradiction:

Improvedevice utilityVSAvoidelectrode interference

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

By inverting the electrode configuration to place electrodes below the piezoelectric layer, the patent eliminates spatial conflict between electrodes and functional structures that would be integrated on or above the piezoelectric layer. This allows functional structures to be added to the exposed top surface without interfering with electrode operation.

Inventive Principle:

Principle #13The other way round (Inversion)

4Reliability

If guided wave confinement structures are added, then acoustic wave confinement is improved, but device complexity increases

Engineering Contradiction:

Improveacoustic wave confinementVSAvoidstructure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent merges the guided wave confinement structures with the existing device architecture by integrating them into the substrate or underlying layers. This combining approach provides effective acoustic wave confinement while minimizing additional structural complexity and maintaining compatibility with the inverted electrode configuration.

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 enhances manufacturing efficiency and allows for the production of devices with adjustable properties and integrated functional structures, improving the utility and performance of MEMS guided wave devices.

Implementation Method 1

Piezoelectric materials acquire a charge when compressed, twisted, or distorted. This property provides a transducer effect between electrical and mechanical oscillations or vibrations.

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Implementation Method 2

Confinement may be provided on at least one surface, such as by reflection at a solid/air interface, or by way of an acoustic mirror (e.g., a stack of layers referred to as a Bragg mirror) capable of reflecting acoustic waves.

Methodology Applied

Scientific EffectAcoustic wave reflection: Reflection

Data Source

PatentUS10530329B2Guided wave devices with selectively thinned piezoelectric layers

Publication Date: 2020.01.07 QORVO US INC

AI summary

A micro-electrical-mechanical system (MEMS) guided wave device includes a plurality of electrodes arranged below a piezoelectric layer (e.g., either embedded in a slow wave propagation layer or supported by a suspended portion of the piezoelectric layer) and configured for transduction of a lateral acoustic wave in the piezoelectric layer. The piezoelectric layer permits one or more additions or modifications to be made thereto, such as trimming (thinning) of selective areas, addition of loading materials, sandwiching of piezoelectric layer regions between electrodes to yield capacitive elements or non-linear elastic convolvers, addition of sensing materials, and addition of functional layers providing mixed domain signal processing utility.