IDT Edge Dielectric Layout for Transverse Mode Suppression
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional acoustic wave devices face challenges in suppressing transverse modes due to high acoustic velocities when SiO2 films are used between IDT electrodes and piezoelectric layers, making it difficult to establish a piston mode.
Innovation Solution
Incorporating dielectric films made of hafnium oxide, niobium oxide, or tungsten oxide between the piezoelectric substrate and electrode fingers in the edge regions, along with specific thickness and material configurations to reduce acoustic velocity and establish a piston mode, thereby preventing transverse modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If an SiO2 film is provided between the IDT electrode and the piezoelectric layer, then the device structure is simple and easy to manufacture, but the acoustic velocity becomes high and the piston mode cannot be established
Solution Approach 1:
The patent applies local quality by providing dielectric films only in the edge regions of the IDT electrode, not in the central region. This creates different acoustic velocity characteristics in different areas: the edge regions have low acoustic velocity due to the dielectric films, while the central region maintains high acoustic velocity for efficient acoustic wave generation. This spatial differentiation resolves the contradiction by allowing the piston mode to be established in the central region while suppressing transverse modes through the low-acoustic-velocity edge regions.
Solution Approach 2:
The patent uses composite material structures by combining different dielectric materials (such as SiO2, Si3N4, Ta2O5) with specific acoustic velocities and impedances. The dielectric films in the edge regions are made from materials selected to provide low acoustic velocity, creating a composite structure that optimizes both the piston mode in the center and transverse mode suppression at the edges, thereby resolving the contradiction between ease of manufacture and acoustic velocity control.
2Ease of manufacture
If an SiO2 film is provided between the IDT electrode and the piezoelectric layer, then the manufacturing process is simplified, but transverse mode spurious cannot be suppressed
Solution Approach 1:
The patent implements local quality by strategically placing dielectric films only in the edge regions where transverse modes originate, while leaving the central region free of dielectric films to maintain piston mode operation. This localized approach suppresses transverse mode spurious through the low-acoustic-velocity edge regions without interfering with the central piston mode, thereby improving reliability while maintaining manufacturing simplicity.
Solution Approach 2:
The patent converts the potentially harmful transverse modes into a beneficial configuration by using the edge regions specifically designed with low-acoustic-velocity dielectric films. These edge regions, which could otherwise be sources of spurious transverse modes, are transformed into active suppression elements that reflect and dampen transverse mode vibrations, turning a problem into a solution while keeping the overall structure manufacturable.
3Reliability
If dielectric films are added to reduce acoustic velocity in edge regions, then the piston mode is enhanced and transverse mode is suppressed, but the device structure becomes more complex
Solution Approach 1:
The patent minimizes device complexity by applying the dielectric film structure only locally in the edge regions rather than throughout the entire electrode area. This selective placement reduces the number of fabrication steps and material layers required compared to a full-coverage dielectric structure, while still achieving the piston mode enhancement and transverse mode suppression needed for improved reliability.
Solution Approach 2:
The patent uses segmentation by dividing the IDT electrode structure into distinct functional zones: a central region without dielectric films for piston mode generation, and edge regions with dielectric films for transverse mode suppression. This segmentation allows each region to be optimized independently and simplifies the overall fabrication process by treating different areas with different structural requirements, thereby reducing device complexity while maintaining reliability.
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
The solution effectively reduces or prevents transverse modes by creating low-acoustic-velocity edge regions, ensuring the establishment of a piston mode and enhancing the acoustic wave device's performance.
Implementation Method 1
an acoustic velocity becomes high. Accordingly, even in a case where an SiO2 film is provided between an IDT electrode and a piezoelectric layer, a piston mode is difficult to be established, and it is difficult to suppress transverse-mode spurious
Implementation Method 2
an Interdigital Transducer (IDT) electrode on the piezoelectric substrate and including a plurality of electrode fingers
Data Source
AI summary
An acoustic wave device includes a piezoelectric substrate and an IDT electrode on the piezoelectric substrate and including electrode fingers. A portion where adjacent electrode fingers of the IDT electrode overlap each other in an acoustic wave propagation direction is an intersecting region. The intersecting region includes a central region located in a central portion in a direction in which the electrode fingers extend and first and second edge regions on both sides of the central region in the direction in which the electrode fingers extend. The acoustic wave device further includes dielectric films between the piezoelectric substrate and the electrode fingers in the first and second edge regions. The dielectric films include at least one of hafnium oxide, niobium oxide, tungsten oxide, or cerium oxide.