Bulk Acoustic Wave Resonator Frame Structure for Spurious Noise Suppression
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Solution Overview
Problem
Small bulk-acoustic wave resonators experience performance deterioration due to increased spurious noise and notch size, primarily because the border of the resonator leaks acoustic energy, affecting vibration form and performance.
Innovation Solution
A bulk-acoustic wave resonator design featuring a second electrode with a frame and trench at the edge of the active region, where the internal boundary line of the trench has a concave-convex shape, such as a sawtooth or wave crest, to suppress spurious noise and notch generation by controlling the angle of inclination and shape of the trench.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the resonator size is reduced, then the device becomes more compact and integrated, but spurious noise and notch size increase due to border effects
Solution Approach 1:
The resonator structure is segmented into multiple functional regions: a resonating region with electrodes and piezoelectric layer for acoustic wave generation, and a separate border region with the frame structure that does not participate in resonating. This segmentation isolates the harmful border effects from the resonating area, allowing small resonator size without proportional increase in spurious noise from borders.
Solution Approach 2:
The frame structure is designed with specific local properties: a first region with larger thickness than a second region, where the thicker first region is positioned to suppress spurious noises and notches while the thinner second region maintains resonating performance. This localized quality variation optimizes different regions for different functions.
2Object-generated harmful factors
If the border thickness is increased to suppress spurious noise, then spurious noise decreases, but the resonating area is reduced and device size increases
Solution Approach 1:
The frame structure employs varying thickness dynamically optimized for different functions: the first region has larger thickness specifically for suppressing spurious noises and notches, while the second region has smaller thickness to minimize space consumption. This dynamic thickness variation allows effective spurious noise suppression without proportional increase in overall device size.
3Ease of manufacture
If a simple rectangular frame is used, then manufacturing is easier, but spurious noise and notch suppression is insufficient
Solution Approach 1:
The frame structure extends into the thickness dimension with varying thickness profiles, creating a three-dimensional structure that provides superior spurious noise suppression compared to simple two-dimensional rectangular frames. The thickness variation in the vertical dimension enables enhanced acoustic energy confinement without significantly increasing planar footprint.
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 design effectively reduces waveform distortion and spurious noise, maintaining performance similar to larger resonators while preventing deterioration at anti-resonance frequencies.
Implementation Method 1
a piezoelectric layer at least partially disposed on an upper portion of the first electrode
Data Source
AI summary
A bulk-acoustic wave resonator includes: a first electrode; a piezoelectric layer at least partially disposed on an upper portion of the first electrode; and a second electrode disposed to cover at least a portion of the piezoelectric layer. The second electrode includes a frame disposed at an edge of an active region of the bulk-acoustic wave resonator, and the first electrode, the piezoelectric layer and the second electrode are disposed to overlap one another at the edge of the active region. The frame includes a wall disposed at the edge of the active region and a trench formed on an internal side of the wall. An internal boundary line of the trench has a concave-convex shape in a plane parallel to an upper surface of the frame.