Acoustic Wave Trench Layout for Transverse Mode Suppression

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Solution Overview

Problem

Existing acoustic wave devices face challenges in suppressing transverse modes without increasing device size or reducing electromechanical coupling coefficients, as current methods either decrease static capacitance or damage central regions during fabrication.

Innovation Solution

The method involves manufacturing an acoustic wave device with trench portions etched into the piezoelectric layer, overlapping with edge regions of interdigital transducer electrodes, which suppresses transverse modes without altering the duty factor in the central region, thus maintaining device size and integrity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If hammer head portions are added to suppress transverse modes, then transverse mode suppression is improved, but device size increases

Engineering Contradiction:

Improvetransverse mode suppressionVSAvoiddevice size

Core Design Contradiction:

ReliabilityVSArea of stationary object

Solution Approach 1:

The patent applies local quality by etching trench portions only in the edge regions of the piezoelectric layer, while leaving the central region intact. This localized modification creates the necessary piston mode distribution for transverse mode suppression without requiring device-wide structural changes, thus avoiding increase in overall device size.

Inventive Principle:

Principle #3Local quality

2Reliability

If duty factor in central region is reduced to achieve transverse mode suppression, then transverse mode suppression is improved, but static capacitance decreases

Engineering Contradiction:

Improvetransverse mode suppressionVSAvoidstatic capacitance

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The patent segments the piezoelectric layer by introducing trench portions only in the edge regions, separating the edge region modifications from the central region. This allows the central region to maintain its original duty factor and static capacitance characteristics while the edge regions provide the necessary acoustic velocity reduction for transverse mode suppression.

Inventive Principle:

Principle #1Segmentation

3Reliability

If mass loading strips are formed on edge regions, then transverse mode suppression is improved, but central region gets damaged during fabrication

Engineering Contradiction:

Improvetransverse mode suppressionVSAvoidcentral region integrity

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The patent extracts the transverse mode suppression function from the central region and relocates it to the edge regions through trench portions. This extraction allows the central region to remain undisturbed during fabrication, as all modifications are confined to the edge regions where the trenches are etched.

Inventive Principle:

Principle #2Taking out (Extraction)

4Reliability

If thicker passivation layer is used in central region, then transverse mode suppression is improved, but electromechanical coupling coefficient is reduced

Engineering Contradiction:

Improvetransverse mode suppressionVSAvoidelectromechanical coupling coefficient

Core Design Contradiction:

ReliabilityVSPower

Solution Approach 1:

The patent applies local quality by concentrating the transverse mode suppression mechanism in the edge regions through trench portions, rather than using a thicker passivation layer across the entire central region. This localized approach achieves the desired piston mode distribution without adding mass loading to the central region, thereby preserving the electromechanical coupling coefficient.

Inventive Principle:

Principle #3Local quality

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 effectively suppresses transverse modes while maintaining high electromechanical coupling coefficients and power durability, and is easier to fabricate without damaging the central region of the interdigital transducer electrodes.

Implementation Method 1

The trench portions 510 slow down the acoustic velocity at edge of the active region to set up piston mode distribution, and thus suppress the transverse modes.

Methodology Applied

Scientific EffectAcoustic velocity reduction: Speed of Sound

Implementation Method 2

An interdigital transducer electrode (IDT) 108 is disposed on top of the layer of piezoelectric material 106

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Data Source

PatentUS20230327630A1Method of manufacture of acoustic wave device with trench portions for transverse mode suppression

Publication Date: 2023.10.12 SKYWORKS SOLUTIONS INC

AI summary

A method of manufacturing an acoustic wave device is provided. The method of manufacturing the acoustic wave device comprises providing a layer of piezoelectric material, disposing a pair of interdigital transducer electrodes on an upper surface of the layer of piezoelectric material, each interdigital transducer electrode including a bus bar and a plurality of electrode fingers extending from the bus bar towards an edge region of the interdigital transducer electrode at the distal ends of the electrode fingers, and etching trench portions into the upper surface of the layer of piezoelectric material, the trench portions overlapping with the edge regions of the interdigital transducer electrodes. The formation of the trench portions through etching results in an easier fabrication, that is less likely to damage the interdigital transducer electrodes.