Piezoelectric Substrate Reforming Regions for Bulk Wave Attenuation
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Solution Overview
Problem
Acoustic wave devices using surface acoustic waves on piezoelectric substrates face degradation due to bulk wave reflections from the lower surface, which can be mitigated by surface modifications but compromise the substrate's strength.
Innovation Solution
The acoustic wave device incorporates reforming regions within the piezoelectric substrate, formed by laser irradiation, to attenuate bulk waves without compromising the substrate's strength by keeping these regions internal and aligned under the Interdigital Transducer (IDT).
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If protrusions and recesses or a reforming layer is located on the lower surface of the piezoelectric substrate to inhibit bulk wave reflection, then the acoustic wave device characteristics are improved, but the strength of the piezoelectric substrate decreases
Solution Approach 1:
The reforming regions are positioned in the thickness direction (depth dimension) of the piezoelectric substrate rather than on the lower surface. This dimensional relocation allows the reforming regions to effectively interact with bulk waves propagating through the substrate while maintaining the integrity and strength of the substrate's lower surface.
Solution Approach 2:
The reforming regions are nested within the bulk of the piezoelectric substrate, specifically positioned under the IDT. This nesting approach allows the reforming regions to be embedded inside the substrate material, enabling bulk wave attenuation without compromising the external surface structure and overall substrate strength.
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 inhibits bulk wave reflections, enhancing filter characteristics while maintaining the substrate's strength and reducing the risk of chipping or cracking.
Implementation Method 1
forming reforming regions only inside the piezoelectric substrate so that the reforming regions are arranged at intervals under the IDT by irradiating the piezoelectric substrate with a laser beam from a lower surface side of the piezoelectric substrate
Implementation Method 2
uses a surface acoustic wave propagating through the upper surface of the piezoelectric substrate
Implementation Method 3
a bulk wave propagating through the inside of the piezoelectric substrate is generated in addition to the surface acoustic wave when the IDT excites the surface acoustic wave
Implementation Method 4
to inhibit the bulk wave from being reflected by the lower surface of the piezoelectric substrate and reaching the upper surface
Data Source
AI summary
An acoustic wave device includes: a piezoelectric substrate; an IDT that is formed on the piezoelectric substrate and includes a pair of comb-shaped electrodes facing each other, each of the pair of comb-shaped electrodes including an grating electrode that excites an acoustic wave and a bus bar to which the grating electrode is connected; and reforming regions that are located only inside the piezoelectric substrate and arranged at intervals under the IDT, and in which a material of the piezoelectric substrate is reformed.