Piezoelectric Thin-Film Resonator Filter Design
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Solution Overview
Problem
Piezoelectric thin-film resonator filters face issues with lateral leakage of acoustic waves and electrostatic discharge (ESD) damage, requiring improved designs to reduce loss and enhance resistance.
Innovation Solution
The filter design incorporates multiple piezoelectric thin-film resonators with specific structural modifications, including first resonators with outer curved portions of the piezoelectric film extending beyond the electrode overlap region and second resonators where the outer curved portions coincide with or extend beyond the electrode overlap region, along with the use of ruthenium electrodes and AlN piezoelectric films, to minimize lateral leakage and enhance ESD resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the piezoelectric film is extended further out than the electrode overlap region, then lateral leakage of acoustic waves is reduced, but the resonator becomes more susceptible to ESD damage
Solution Approach 1:
The resonator structure is segmented into two types: first resonators with piezoelectric film extending beyond the electrode overlap region to reduce lateral leakage, and second resonators with piezoelectric film coinciding with the electrode overlap region to provide ESD protection. This segmentation allows each type to optimize for its specific function while working together in the filter assembly.
Solution Approach 2:
Different regions of the filter are assigned different resonator types based on local requirements. The first resonators are placed in positions where lateral leakage reduction is critical, while second resonators are positioned where ESD protection is prioritized, creating local quality variations throughout the filter structure.
2Reliability
If the piezoelectric film outer curved portion coincides with the electrode overlap region, then ESD resistance is improved, but lateral leakage increases
Solution Approach 1:
The resonator structure is segmented into two types: first resonators with piezoelectric film extending beyond the electrode overlap region to reduce lateral leakage, and second resonators with piezoelectric film coinciding with the electrode overlap region to provide ESD protection. This segmentation allows each type to optimize for its specific function while working together in the filter assembly.
Solution Approach 2:
Different regions of the filter are assigned different resonator types based on local requirements. The first resonators are placed in positions where lateral leakage reduction is critical, while second resonators are positioned where ESD protection is prioritized, creating local quality variations throughout the filter structure.
3Ease of manufacture
If all resonators use the same structure, then manufacturing is simplified, but performance cannot simultaneously optimize both lateral leakage reduction and ESD resistance
Solution Approach 1:
The resonator structure is segmented into two types: first resonators with piezoelectric film extending beyond the electrode overlap region to reduce lateral leakage, and second resonators with piezoelectric film coinciding with the electrode overlap region to provide ESD protection. This segmentation allows each type to optimize for its specific function while working together in the filter assembly.
Solution Approach 2:
Different regions of the filter are assigned different resonator types based on local requirements. The first resonators are placed in positions where lateral leakage reduction is critical, while second resonators are positioned where ESD protection is prioritized, creating local quality variations throughout the filter structure.
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 design effectively reduces lateral leakage and significantly improves resistance to ESD damage, with the first embodiment showing 20% fault rate at 200V and some filters resistant to 600V, compared to all-second-resonator filters which fail at 200V.
Implementation Method 1
piezoelectric thin-film resonators each having a substrate, a lower electrode formed on the substrate, a piezoelectric film formed on the lower electrode, and an upper electrode provided on the piezoelectric film so that the upper electrode and the lower electrode face each other across the piezoelectric film
Data Source
AI summary
A filter includes multiple piezoelectric thin-film resonators each having a substrate, a lower electrode formed on the substrate, a piezoelectric film formed on the lower electrode, and an upper electrode provided on the piezoelectric film so that the upper electrode and the lower electrode face each other across the piezoelectric film. The multiple piezoelectric thin-film resonators include a first resonator in which at least a part of an outer curved portion of the piezoelectric film of the first resonator is located further out than an outer curved portion of a region in which the upper electrode and the lower electrode face each other across the piezoelectric film. The multiple piezoelectric thin-film resonators includes a second resonator in which at least a part of an outer curved portion of the piezoelectric film of the second resonator substantially coincides with an outer curved portion of a region in which the upper electrode and the lower electrode face each other across the piezoelectric film or is further in than the outer curved portion of the region.