LiNbO3 Boundary Wave Structure for Stoneley Wave Suppression
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Solution Overview
Problem
Elastic boundary wave devices face challenges in suppressing Stoneley waves, which degrade the frequency characteristics and increase production costs due to the need for hermetically sealed packages to prevent foreign material adherence, limiting device miniaturization.
Innovation Solution
The design incorporates a LiNbO3 substrate with a silicon oxide film and specific electrode parameters, including copper density ratio, wavelength, film thickness, and Y-cut angle, to suppress Stoneley waves by controlling the electromechanical coupling coefficient k2 within certain ranges, thereby reducing unwanted wave responses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If hermetically sealed package is used to prevent foreign material adherence, then reliability is improved, but device size increases and production cost increases
Solution Approach 1:
The patent extracts and eliminates the hermetically sealed package by depositing a silicon oxide film directly on the substrate surface. This removes the need for encapsulation while preventing foreign material adherence, thereby reducing device size and production cost while maintaining reliability.
Solution Approach 2:
The silicon oxide film acts as an intermediary layer between the substrate and the external environment. It provides protection against foreign material adherence without requiring a hermetic seal, thus resolving the contradiction between reliability and device size.
2Device complexity
If Stoneley wave suppression is not implemented, then device complexity is reduced, but frequency characteristics degrade
Solution Approach 1:
The patent changes the physical and chemical parameters of the substrate surface by depositing a silicon oxide film with specific thickness and properties. This modifies the acoustic impedance and suppresses Stoneley wave generation, improving frequency characteristics without significantly increasing device complexity.
Solution Approach 2:
The patent uses a composite structure consisting of the substrate and the silicon oxide film layer. This composite material approach suppresses Stoneley waves while maintaining relatively simple device structure, resolving the contradiction between device complexity and frequency characteristics.
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 minimizes Stoneley wave interference, improving frequency characteristics and allowing for smaller device sizes without increasing production costs, as the device can operate within specified parameter ranges to maintain k2 below a certain threshold.
Implementation Method 1
an elastic boundary wave device including: a LiNbO3 substrate; an electrode exciting an elastic wave and provided on the substrate; and a silicon oxide film provided on the substrate to cover the electrode, wherein parameters of the elastic boundary wave device have any one of ranges below... in which Stoneley wave can be suppressed
Implementation Method 2
an electrode exciting an elastic wave and provided on the substrate... SH of FIG. 1 represents a response of a wave having a main component of Shear Horizontal (SH) wave utilized in the elastic boundary wave device
Implementation Method 3
a LiNbO3 substrate... elastic waves concentrate and propagate along the substrate surface
Data Source
AI summary
An elastic boundary wave device includes a LiNbO3 substrate, an electrode exciting an elastic wave and provided on the substrate, and a silicon oxide film provided on the substrate to cover the electrode, and parameters of the elastic boundary wave device have any one of ranges, where “θ” is a rotation Y cut angle of the substrate, “a” is a ratio of copper density with respect to a density of a material used as the electrode, “λ” is a wavelength of the elastic wave excited by the electrode, “h” is a film thickness of the electrode, “H” is a thickness of the silicon oxide film.