SAW Acoustic Layer Stack for Higher Q and Lower Energy Leakage

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Solution Overview

Problem

Existing surface acoustic wave (SAW) devices face challenges in achieving high Q performance due to the high viscosity of low sound velocity layers, which leads to energy leakage and reduced device efficiency.

Innovation Solution

The proposed SAW device incorporates a structure with multiple low sound velocity layers, where the second low sound velocity layer is formed using Physical Vapor Deposition (PVD) to have a higher sound velocity and lower viscosity compared to the first low sound velocity layer formed by Chemical Vapor Deposition (CVD).

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If a single low sound velocity layer is used in the SAW device structure, then the device can be manufactured with simpler process, but the Q performance deteriorates due to high viscosity and energy leakage

Engineering Contradiction:

Improvemanufacturing simplicityVSAvoidQ performance

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The single low sound velocity layer is segmented into multiple layers with different sound velocities. The patent uses a first low sound velocity layer (SiO2) and a second low sound velocity layer (Si3N4) with different acoustic properties, where the second layer has higher sound velocity to reduce energy leakage and improve Q performance while maintaining manufacturing feasibility

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent employs composite material structure by combining different materials (SiO2 and Si3N4) with complementary properties in the low sound velocity layers. This composite approach allows optimization of both Q performance through reduced viscosity and energy leakage, and manufacturing ease through compatibility with existing CVD and PVD processes

Inventive Principle:

Principle #40Composite materials

2Ease of manufacture

If CVD process is used to manufacture the low sound velocity layer, then the manufacturing cost is reduced, but the viscosity increases leading to energy leakage

Engineering Contradiction:

Improvemanufacturing costVSAvoidenergy leakage

Core Design Contradiction:

Ease of manufactureVSLoss of energy

Solution Approach 1:

Different deposition methods are applied to different layers based on their specific functional requirements. The first low sound velocity layer uses CVD for cost-effective manufacturing, while the second low sound velocity layer uses PVD to achieve lower viscosity and reduced energy leakage, optimizing both cost and performance locally

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent changes the deposition method parameter from CVD to PVD for the second low sound velocity layer, which fundamentally alters the material properties by reducing viscosity. This parameter change directly addresses energy leakage while maintaining manufacturing feasibility through PVD technology

Inventive Principle:

Principle #35Parameter changes

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 enhances the Q performance of the SAW device by reducing energy leakage and improving resonance frequency, while also increasing the bonding strength and reliability of the device.

Implementation Method 1

the second low sound velocity layer formed using Physical Vapor Deposition (PVD) to have a higher sound velocity and lower viscosity compared to the first low sound velocity layer formed by Chemical Vapor Deposition (CVD)

Methodology Applied

Scientific EffectPhysical Vapor Deposition: Physical Vapour Deposition

Implementation Method 2

the first low sound velocity layer formed by Chemical Vapor Deposition (CVD)

Methodology Applied

Scientific EffectChemical Vapor Deposition: Chemical Vapour Deposition

Implementation Method 3

a piezoelectric plate formed on the second low sound velocity layer; and a plurality of IDT electrode fingers formed on the piezoelectric plate

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Data Source

PatentUS20250030397A1Surface acoustic wave device having improved q performance and method of manufacturing the same

Publication Date: 2025.01.23 WISOL CO LTD

AI summary

A Surface Acoustic Wave (SAW) device having improved Q performance and high reliability of a bonding unit and a method of manufacturing the same are provided. The surface acoustic wave device includes a support substrate; a high sound velocity layer formed on the support substrate; a first low sound velocity layer formed on the high sound velocity layer; a second low sound velocity layer formed on the first low sound velocity layer; a piezoelectric plate formed on the second low sound velocity layer; and a plurality of IDT electrode fingers formed on the piezoelectric plate, and the sound velocity of the first low sound velocity layer and the sound velocity of the second low sound velocity layer are different from each other.