Zig-Zag Electrode BAW Resonator Spurious Mode Control
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Solution Overview
Problem
Bulk acoustic wave (BAW) resonators and filters are susceptible to unwanted lateral wave propagation, which degrades their quality factor (Q) and leads to unreliable frequency response due to spurious resonance modes, especially with conventional rectangular electrodes.
Innovation Solution
Designing BAW resonators with patterned edges, such as zig-zag or non-parallel curved edges, and using a pulse function to create a closed-loop contour line that defines the electrode perimeter, which helps in attenuating spurious modes and improving the Q factor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional rectangular electrodes are used in BAW resonators, then the device structure is simple and easy to manufacture, but lateral wave propagation increases causing reduced Q factor and spurious resonance modes
Solution Approach 1:
The patent applies asymmetry by changing the electrode geometry from conventional rectangular shapes to irregular polygonal shapes with non-parallel sides and non-equal angles. This asymmetric design disrupts the symmetry of lateral wave propagation paths, causing waves to travel different distances and arrive at different times, thereby reducing coherent spurious modes and improving Q factor while maintaining manufacturing feasibility through standard photolithography processes
Solution Approach 2:
The patent employs curvature principles by designing electrode edges with rounded corners and curved segments rather than sharp直角. The irregular polygonal shape incorporates curved boundaries that scatter lateral waves more effectively, reducing their coherence and preventing the formation of strong spurious resonance modes, thus improving frequency response reliability
2Reliability
If peripheral rings are added to rectangular electrodes to reduce lateral waves, then the Q factor improves, but the device complexity and manufacturing steps increase
Solution Approach 1:
The patent merges the functions of the electrode pattern and the lateral wave suppression structure into a single integrated irregular polygonal electrode design. Instead of adding separate peripheral rings or acoustic absorbers as additional components, the wave-suppressing geometry is built into the electrode itself through its irregular shape, reducing device complexity while achieving improved Q factor
Solution Approach 2:
The irregular polygonal electrode serves multiple functions simultaneously: it provides the necessary electrical connection as an electrode while its specific geometric shape inherently suppresses lateral wave propagation. This multi-functional design eliminates the need for separate wave-suppression components, reducing overall device complexity while maintaining high Q factor
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
The solution results in a higher Q factor and smoother frequency response, reducing unwanted lateral wave propagation and achieving improved performance comparable to polygonal-shaped electrodes without the need for additional components like border rings.
Implementation Method 1
The launch wave 503 of electrode 501 is launched and reflected back in a parallel manner as shown by reflected wave 505
Implementation Method 2
The peripheral ring 509 is provided as an acoustic absorber to change acoustic boundary conditions
Data Source
AI summary
Method of designing a BAW resonator and filter and the resulting devices are provided. Embodiments include patterning a bottom electrode of a resonator, patterning a top electrode of the resonator, and intersecting area of the resonator, wherein the effective area includes a closed-loop contour line including a pulse function pattern with predefined amplitude, period and a number of repetitions of pulses along the closed-loop contour line.