SAW IDT Electrode Layout for Transverse Spurious Signal Suppression
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Solution Overview
Problem
Acoustic wave devices, such as SAW resonators, face challenges in suppressing transverse mode spurious signals, which interfere with their operation, especially when using tungsten layers in IDT electrodes, where previous configurations with high acoustic wave velocity materials in center regions become less effective.
Innovation Solution
The solution involves modifying the acoustic wave device by increasing the duty factor and thickness of IDT electrodes in edge regions, using high-density materials in edge regions, and incorporating dummy IDT electrodes with reduced widths in gap regions to reduce acoustic velocity and enhance the velocity difference between center and edge regions, thereby suppressing transverse mode spurious signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If high acoustic wave velocity materials are used in center regions, then operating frequency is maintained, but transverse mode spurious signals are not suppressed
Solution Approach 1:
The patent applies local quality by creating distinct regions with different properties: center regions maintain high acoustic velocity for frequency operation, while edge regions use low acoustic velocity materials to suppress spurious signals. This spatial differentiation of material properties resolves the contradiction between maintaining operating frequency and suppressing harmful signals.
Solution Approach 2:
The IDT electrode structure is segmented into center regions and edge regions with different duty factors. The center regions have lower duty factors to maintain acoustic velocity for frequency operation, while edge regions have higher duty factors to reduce acoustic velocity and suppress spurious signals, thereby resolving the technical contradiction.
2Object-generated harmful factors
If IDT electrode duty factor is increased in edge regions, then spurious signals are suppressed, but device complexity increases
Solution Approach 1:
Rather than uniformly complicating the entire IDT structure, the patent applies local quality by modifying only the edge regions with higher duty factors while keeping center regions simpler with lower duty factors. This localized modification suppresses spurious signals without unnecessarily increasing overall device complexity.
3Object-generated harmful factors
If acoustic wave velocity is reduced in edge regions, then spurious signals are suppressed, but quality factor decreases
Solution Approach 1:
The patent segments the acoustic wave propagation path into center regions where high velocity maintains quality factor, and edge regions where low velocity suppresses spurious signals. This segmentation allows both objectives to be achieved simultaneously by assigning different velocity characteristics to different spatial zones.
Solution Approach 2:
By applying local quality with region-specific acoustic velocity characteristics, the patent ensures that the quality factor is maintained in center regions through high velocity materials, while spurious signals are suppressed in edge regions through low velocity materials, resolving the apparent contradiction.
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 the strength of transverse mode spurious signals and improves the quality factor of the acoustic wave devices, maintaining operating frequency while reducing component size.
Implementation Method 1
a substrate including a piezoelectric material, interdigital transducer (IDT) electrodes disposed on an upper surface of the substrate
Implementation Method 2
Acoustic wave devices, for example, surface acoustic wave (SAW) and bulk acoustic wave (BAW) devices may be utilized as components of filters in radio frequency electronic systems
Data Source
AI summary
An acoustic wave device comprises a substrate including a piezoelectric material, interdigital transducer (IDT) electrodes disposed on an upper surface of the substrate. The IDT electrodes having gap regions, edge regions, and center regions. A duty factor of the IDT electrodes in the edge regions is greater than the duty factor of the IDT electrodes in the center regions. A first dielectric film is disposed above the IDT electrodes and an upper surface of the substrate. The first dielectric film has a greater thickness in portions of the center regions than in portions proximate the gap regions.