DBAR Electrode Edge Alignment for Rp and kt2 Tradeoffs
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Solution Overview
Problem
There is a tradeoff between parallel resistance (Rp) and electromechanical coupling coefficient (kt2) in acoustic resonators, making it challenging to achieve optimal values for different applications, as increasing one typically decreases the other.
Innovation Solution
The alignment of electrode edges in Double Bulk Acoustic Resonator (DBAR) structures, such as the Δ, ∇, Ξ, and Θ configurations, is optimized to enhance either Rp or kt2, allowing for tailored performance in various applications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the resonator structure is optimized to increase parallel resistance (Rp), then the quality factor improves, but the electromechanical coupling coefficient (kt2) decreases
Solution Approach 1:
The patent divides the resonator into two separate resonator structures (first and second resonators) with different electrode edge alignments. The first resonator is optimized for high parallel resistance with its specific alignment configuration, while the second resonator is optimized for high electromechanical coupling coefficient with its different alignment configuration. This segmentation allows both conflicting performance parameters to be optimized in separate devices.
Solution Approach 2:
The patent applies different local quality characteristics to different parts of the resonator structure by varying the electrode edge alignments. The first resonator uses a first alignment configuration that creates specific local stress distributions and acoustic field patterns optimized for high Rp, while the second resonator uses a second alignment configuration that creates different local patterns optimized for high kt2. Each local structure is tailored to its specific performance goal.
2Productivity
If the electrode edge alignment is changed to enhance electromechanical coupling coefficient (kt2), then the coupling efficiency improves, but the parallel resistance (Rp) decreases
Solution Approach 1:
The patent segments the resonator system into two distinct resonator structures, each with electrode edge alignments specifically configured to optimize for either electromechanical coupling coefficient or parallel resistance. This allows the second resonator to achieve high kt2 through its alignment configuration while the first resonator maintains high Rp through its different alignment, resolving the tradeoff through system-level segmentation.
Solution Approach 2:
The patent inverts the conventional approach by creating two separate resonator structures with opposite or different alignment configurations rather than trying to optimize a single structure for both parameters. The first resonator uses alignment optimized for Rp while the second uses alignment optimized for kt2, effectively inverting the optimization priority to resolve the contradiction.
3Adaptability or versatility
If a single resonator structure is used, then the device complexity is low, but it cannot simultaneously achieve optimal values for both parallel resistance (Rp) and electromechanical coupling coefficient (kt2)
Solution Approach 1:
The patent divides the acoustic resonator system into multiple resonator structures (first and second resonators) with different electrode edge alignments. Each resonator is specialized for a specific performance parameter, allowing the system to achieve optimal values for both parallel resistance and electromechanical coupling coefficient simultaneously, despite the increased structural complexity.
Solution Approach 2:
The patent creates a multi-functional resonator system where the first resonator handles the function of providing high parallel resistance while the second resonator handles the function of providing high electromechanical coupling coefficient. This universal approach allows the overall system to fulfill multiple performance requirements that a single resonator cannot satisfy alone.
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
These configurations effectively increase parallel resistance or electromechanical coupling coefficient, enabling improved performance in RF and microwave devices by suppressing spurious lateral modes and optimizing resonator efficiency.
Implementation Method 1
In response to this electrical field, the reciprocal or inverse piezoelectric effect causes acoustic resonator 10 to mechanically expand or contract depending on the polarization of the piezoelectric material
Implementation Method 2
As the electrical field varies over time, an acoustic wave is generated in piezoelectric layer 12, and the acoustic wave propagates through acoustic resonator 10
Implementation Method 3
For longitudinal waves, where a thickness d of piezoelectric layer 12 and of the top and bottom electrodes equals an odd (1, 3, 5 . . . ) integer multiple of half the wavelength λ of the acoustic waves, resonance states and/or acoustic resonance vibrations will occur
Data Source
AI summary
An acoustic resonator comprises a substrate having a trench with lateral boundaries, a first electrode formed on the substrate over the trench and having lateral edges that are laterally offset from the lateral boundaries of the trench by a first distance, a first piezoelectric layer formed on the first electrode, a second electrode formed on the first piezoelectric layer and having edges that are laterally aligned inside the lateral boundaries of the trench, a second piezoelectric layer located on the second electrode, and a third electrode located on the second piezoelectric layer and having edges that are laterally offset from the edges of the second electrode.