Back-Side Dielectric Coating for Acoustic Resonator Frequency Tuning
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing RF filters face challenges in achieving precise control over resonance frequencies and spurious responses due to non-uniform dielectric coatings on interdigital transducers, particularly in shunt resonators, which affect the performance of acoustic wave resonators.
Innovation Solution
The implementation of a uniform dielectric coating on the back-side of piezoelectric plates, with varying thicknesses for shunt and series resonators, to achieve controlled resonance frequencies and improved manufacturing consistency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a dielectric coating is applied to the interdigital transducers, then the resonance frequency can be adjusted, but the coating becomes non-uniform which causes spurious responses and reduces manufacturing precision
Solution Approach 1:
The patent applies dielectric coating to the back-side of the piezoelectric plate rather than on the interdigital transducers themselves. This dimensional shift from front-side to back-side coating eliminates the non-uniformity problem while still achieving resonance frequency tuning through the added dielectric layer.
Solution Approach 2:
The patent uses selective thickness control of the back-side dielectric coating layer, where different regions have different thicknesses to achieve desired resonance characteristics. This localized variation in coating thickness allows precise frequency control without the uniformity issues of front-side coating.
2Measurement precision
If the dielectric coating thickness is increased to tune the resonance frequency, then the frequency accuracy improves, but the spurious responses increase due to coating non-uniformity
Solution Approach 1:
By moving the dielectric coating application to the back-side of the piezoelectric plate, the patent achieves better uniformity in the coating thickness. This dimensional change allows for more precise control of resonance frequency without the spurious responses that plague front-side coating approaches.
3Ease of manufacture
If conventional front-side dielectric coating is used, then the process is simple, but the non-uniform coating reduces reliability of resonator performance
Solution Approach 1:
The patent maintains manufacturing simplicity by using standard dielectric coating processes, but applies them to the back-side of the piezoelectric plate instead of the front-side. This dimensional shift preserves ease of manufacture while dramatically improving coating uniformity and thus resonator performance 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
This approach enhances the accuracy of resonance frequency tuning and reduces spurious responses, leading to improved performance and manufacturing efficiency of RF filters.
Implementation Method 1
at least one piezoelectric plate having opposing first and second surfaces and attached to the substrate
Implementation Method 2
the at least one second dielectric coating layer of the shunt resonator has a greater thickness than a thickness of the at least one second dielectric coating layer of the series resonator
Data Source
AI summary
A filter device is provided a substrate; a piezoelectric layer attached to the substrate; a conductor pattern on a first surface of the piezoelectric layer and including a plurality of interdigital transducers of a plurality of resonators that each have interleaved fingers at s respective diaphragm; a first dielectric layer over at least the interleaved fingers of the plurality of interdigital transducers and on the first surface of the piezoelectric layer; and a second dielectric layer on the second surface of the piezoelectric layer that is opposite the first surface. The second dielectric layer provides a more uniform dielectric coating on the second surface of the piezoelectric layer than a coating of the at least one first dielectric layer that is over the interleaved fingers.