Acoustic Wave IDT Edge Trenches for Transverse Mode Suppression
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing acoustic wave devices face challenges in effectively suppressing transverse modes without increasing device size, reducing static capacitance, or damaging central regions during fabrication.
Innovation Solution
Incorporating trench portions in the piezoelectric layer that overlap with the edge regions of interdigital transducer electrodes, where the electrode fingers have smaller widths in these regions, maintaining a duty factor of 0.5 in the central region, and forming trench portions through etching after IDT formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If hammer head portions are added to suppress transverse modes, then transverse mode suppression is improved, but device size increases
Solution Approach 1:
The patent applies local quality by creating hammer head portions only in the edge regions of the IDT, while maintaining a different structure in the central region. This localized modification suppresses transverse modes at the edges where they originate, without requiring global changes to the entire IDT structure, thereby limiting the increase in device size.
Solution Approach 2:
The IDT is segmented into different functional regions: a central region with uniform finger width and edge regions with hammer head portions. This segmentation allows each region to serve its specific purpose - the central region maintains high static capacitance while the edge regions provide transverse mode suppression, resolving the contradiction between suppression effectiveness and device size.
2Reliability
If duty factor in central region is reduced below 0.5 to achieve transverse mode suppression, then transverse mode suppression is improved, but static capacitance decreases
Solution Approach 1:
The patent maintains a duty factor of 0.5 in the central region to preserve static capacitance, while applying transverse mode suppression structures (hammer head portions) only in the edge regions. This local differentiation allows the central region to maintain high capacitance while the edge regions provide the necessary mode suppression.
Solution Approach 2:
The IDT is divided into central and edge regions with different structural characteristics. The central region maintains DF=0.5 for high static capacitance, while the edge regions incorporate hammer head portions for transverse mode suppression. This segmentation resolves the contradiction by assigning different functions to different regions.
3Reliability
If mass loading strips are formed on edge regions to suppress transverse modes, then transverse mode suppression is improved, but central region may be damaged during fabrication
Solution Approach 1:
The IDT electrodes are formed first, creating a protective structure over the central region of the piezoelectric layer. Subsequently, the hammer head portions are added to the edge regions. This preliminary formation of the IDT provides a protective mask during the fabrication of the suppression structures, preventing damage to the central region.
Solution Approach 2:
The IDT electrode structure serves as an intermediary protective layer during the fabrication process. When forming the hammer head portions in the edge regions, the existing IDT electrodes protect the central region from fabrication damage, while still allowing the suppression structures to be formed in the edge regions where needed.
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 suppresses transverse modes, maintains device size, prevents central region damage, and enhances electromechanical coupling coefficient and quality factor, resulting in improved performance.
Implementation Method 1
a layer of piezoelectric material, a pair of interdigital transducer electrodes disposed on an upper surface of the layer of piezoelectric material
Implementation Method 2
The hammer head portions 110 of the device of FIGS. 1A and 1B reduce the acoustic velocity in the edge regions E compared to the central region C. This velocity reduction creates a piston mode distribution to reduce transverse modes.
Data Source
AI summary
An acoustic wave device, a radio frequency filter and an electronics module are provided. The acoustic wave device, comprises a layer of piezoelectric material, a pair of interdigital transducer electrodes disposed on an upper surface of the layer of piezoelectric material, each interdigital transducer electrode including a bus bar and a plurality of electrode fingers extending from the bus bar through a central region of the interdigital transducer electrode towards an edge region of the interdigital transducer electrode, each of the plurality of electrode fingers having a width in a direction perpendicular to the extension of the electrode fingers that is smaller in the edge regions than in the central regions, and trench portions located in the upper surface of the layer of piezoelectric material, the trench portions overlapping with the edge regions of the interdigital transducer electrodes. The acoustic wave device provides effective suppression of transverse modes.