SAW Capacitance Element Layout to Suppress Resonance
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Solution Overview
Problem
Existing acoustic wave devices face challenges in reducing resonance through the capacitance element, leading to a decrease in acoustic wave device characteristics, and the use of a separate conductive layer for the capacitance element increases manufacturing costs.
Innovation Solution
An acoustic wave device configuration featuring a piezoelectric substrate with an excitation electrode and a capacitance element connected in parallel, where an insulator is superimposed only on the capacitance element between the excitation electrode and the capacitance element, reducing resonance and eliminating the need for a separate conductive layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the capacitance element is provided on the piezoelectric substrate, then the capacitance element can be integrated with the excitation electrode, but the capacitance element excites acoustic waves and resonates, causing characteristics of the acoustic wave device to deteriorate
Solution Approach 1:
An insulator layer is introduced as an intermediary between the capacitance element and the piezoelectric substrate. This insulator prevents direct mechanical coupling, thereby suppressing acoustic wave excitation and resonance in the capacitance element while maintaining electrical connection and integration benefits.
2Reliability
If the capacitance element is separated from the piezoelectric substrate, then the Q value of the capacitance element is raised in high frequency band, but a separate conductive layer must be used and the structure becomes three-dimensional, increasing manufacturing cost
Solution Approach 1:
The insulator layer acts as a mediator that allows the capacitance element to be positioned above the piezoelectric substrate without direct contact, achieving acoustic isolation and high Q value while maintaining a planar two-dimensional structure that is compatible with standard manufacturing processes.
Solution Approach 2:
The capacitance element is positioned in the vertical dimension above the piezoelectric substrate rather than being laterally separated, achieving acoustic isolation while maintaining manufacturing simplicity through a planar structure.
3Object-generated harmful factors
If the electrode fingers in the capacitance element are inclined relative to the excitation electrode, then influence of reflection wave of SAW in the capacitance element is reduced, but the structure becomes more complex
Solution Approach 1:
The insulator layer serves as an intermediary that suppresses acoustic wave generation at the source, making additional complexity in electrode finger orientation unnecessary for reducing reflection wave influence.
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 effectively reduces resonance and insertion loss, while minimizing spurious emission and manufacturing costs, resulting in improved electrical characteristics and device performance.
Implementation Method 1
a capacitance element which is located on the major surface and is connected to the excitation electrode, and an insulator which is superimposed only on the capacitance element between the excitation electrode and the capacitance element
Data Source
AI summary
An SAW device includes a piezoelectric substrate, an IDT electrode on a first major surface of the piezoelectric substrate, a capacitance element which is located on the first major surface and is connected to the IDT electrode, and a cover which is superimposed only on the capacitance element between the IDT electrode and the capacitance element.