IDT Mass-Loading Layout for Transverse Spurious Mode Suppression
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing elastic wave devices using piston mode face challenges in suppressing transverse mode spurious responses due to variations in film thickness during the manufacturing process, which affects the acoustic velocities in different regions of the intersection area.
Innovation Solution
The elastic wave device incorporates first, second, and third mass adding films with specific dimensions and densities on a piezoelectric substrate, where the second and third mass adding films cover entire edge regions, ensuring acoustic velocities in these regions are lower than in the center region, thereby reducing transverse mode spurious responses and improving excitation efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If titanium layers are embedded in the first and second edge regions to suppress transverse mode spurious responses, then transverse mode spurious responses are reduced, but film thickness variations increase in the intersection region
Solution Approach 1:
The intersection region is divided into three distinct regions (first edge region, center region, second edge region) with different mass adding film configurations. Each region has tailored acoustic velocity characteristics through selective placement of mass adding films, allowing independent optimization of spurious response suppression and manufacturing precision for each segment.
Solution Approach 2:
Different regions of the IDT electrode are given different local properties through selective mass adding film placement. The first and second edge regions have mass adding films to reduce acoustic velocity and suppress spurious responses, while the center region maintains different characteristics for optimal main mode operation. This local differentiation allows each region to perform its specific function while maintaining overall device performance.
2Object-generated harmful factors
If different processes are used for center region and edge regions to achieve different acoustic velocities, then transverse mode spurious responses are suppressed, but manufacturing complexity increases
Solution Approach 1:
The mass adding films for the first edge region, center region, and second edge region are combined into a single continuous film structure that can be formed by one deposition process. This unified approach allows different regional functions to be achieved through a single manufacturing step, reducing process complexity while maintaining the acoustic velocity differentiation needed for spurious response suppression.
Solution Approach 2:
The mass adding film structure serves multiple functions simultaneously: it suppresses transverse mode spurious responses in the edge regions, maintains proper acoustic velocity in the center region, and can be formed by a single manufacturing process. This multi-functionality reduces the need for separate processes while achieving all required acoustic velocity control objectives.
3Object-generated harmful factors
If mass adding films are placed in edge regions to reduce acoustic velocity, then transverse mode spurious responses are reduced, but excitation efficiency may be affected
Solution Approach 1:
The mass adding films are placed only in the first and second edge regions where spurious responses originate, while the center region maintains its original acoustic velocity characteristics for efficient excitation. This localized approach ensures that spurious response suppression does not compromise the excitation efficiency of the main operating mode, as the center region where most of the energy is concentrated remains unaffected.
Solution Approach 2:
The mass adding films in the edge regions convert the potentially harmful transverse mode spurious responses into beneficial acoustic velocity differentiation. By reducing acoustic velocity in the edge regions, the spurious responses are suppressed while the main mode operation in the center region continues with high efficiency, effectively turning a potential problem into a solution.
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 or prevents transverse mode spurious responses, enhances excitation efficiency, and allows for easier film formation using the lift-off method, thus improving productivity while minimizing the influence of film thickness variations.
Implementation Method 1
a first mass adding film that is provided on the first dielectric film, extends along the direction in which the first and second electrode fingers extend, and is provided in the center region, and overlaps with the plurality of first and second electrode fingers when seen from above, a second mass adding film that is provided on the first dielectric film and in the first edge region, and a portion of which overlaps with at least one of the first and second electrode fingers when seen from above, and a third mass adding film that is provided on the first dielectric film and in the second edge region, and a portion of which overlaps with at least one of the first and second electrode fingers when seen from above
Implementation Method 2
an elastic wave device includes a piezoelectric substrate, and an IDT electrode that is provided on the piezoelectric substrate
Data Source
AI summary
An elastic wave device includes first mass adding films provided on a first dielectric film to overlap with first and second electrodes fingers of an IDT electrode when seen from above, extend in a direction in which the first and second electrode fingers extend, and are provided in a center region, and second and third mass adding films that are provided on the first dielectric film and are provided in first and second edge regions, respectively, and a portion of which overlap with at least one of the first and second electrode fingers when seen from above. Dimensions of the second and third mass adding films along an elastic wave propagation direction are larger than a dimension of the first mass adding films along the elastic wave propagation direction.