Multilayer Cavity Resonator Structure for Piezoelectric Stress Control
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Solution Overview
Problem
The manufacturing of high-performance resonators with aboveground cavities faces challenges due to large morphological changes and stress-related defects in the piezoelectric layer, leading to energy leakage and mechanical breakage, particularly in high-frequency devices.
Innovation Solution
A resonator design featuring a multilayer cavity with a gradually decreasing width away from the substrate, incorporating a first cavity surrounding a second cavity, and a release channel with reduced height to minimize stress changes in the piezoelectric layer, along with a method involving sacrificial layers and controlled etching to form the cavity structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If the side of the aboveground cavity has a large inclination angle to ensure cavity height, then the cavity height is maintained, but the piezoelectric layer experiences large morphological changes and stress concentration leading to cracks and defects
Solution Approach 1:
The cavity structure is divided into multiple layers with different width dimensions. The multilayer cavity includes a first cavity layer and a second cavity layer, where each layer has a specific width that gradually decreases from bottom to top. This segmentation allows the cavity height to be maintained while reducing the inclination angle of each individual layer, thereby minimizing stress concentration in the piezoelectric layer.
Solution Approach 2:
The width parameter of the cavity is changed across different layers. The first cavity layer has a first width and the second cavity layer has a second width that is smaller than the first width. This parameter change creates a gradual transition in cavity dimensions, reducing the inclination angle and minimizing morphological changes in the piezoelectric layer while maintaining the required cavity height.
2Area of stationary object
If the release hole is defined on the periphery of the resonator to ensure active region area, then the active region area is maximized, but the cavity must protrude outward causing sudden stress change and mechanical breakage
Solution Approach 1:
The cavity structure is segmented into multiple layers with progressively decreasing widths. This segmentation allows the cavity to maintain its height and functional volume while reducing the need for outward protrusion. The gradual width reduction distributes stress more evenly across the piezoelectric layer, preventing sudden stress changes and mechanical breakage at protruded regions.
Solution Approach 2:
Instead of solving the release hole placement problem in the horizontal plane (periphery vs. center), the solution transitions to the vertical dimension by creating a multilayer cavity structure. The width reduction occurs in the vertical direction across layers, allowing the release hole to be positioned optimally while maintaining both active region area and structural reliability.
3Reliability
If the cavity width is reduced to minimize stress changes, then stress distribution is improved, but the cavity height may be compromised
Solution Approach 1:
The cavity is divided into multiple layers where the width reduction is distributed across layers rather than applied uniformly. The first cavity layer maintains a larger width to support cavity height, while the second cavity layer has a smaller width to reduce stress. This segmentation allows both cavity height and improved stress distribution to be achieved simultaneously.
Solution Approach 2:
The cavity width parameter is changed across different layers while maintaining the cavity height parameter. The first width (larger) and second width (smaller) are applied to different layers, creating a gradient structure that improves stress distribution without compromising the overall cavity height required for resonator functionality.
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 reduces stress changes in the piezoelectric layer, enhancing its performance and mechanical stability, while allowing for miniaturization and improved reliability of the resonator, particularly in high-frequency applications.
Implementation Method 1
a piezoelectric layer arranged between the bottom electrode and the top electrode
Implementation Method 2
An acoustic reflection structure is arranged below the bottom electrode to prevent the energy from leaking to the substrate, so that the energy is stored in the resonator
Data Source
AI summary
A resonator is provided. The resonator includes a substrate, a bottom electrode, a piezoelectric layer and a top electrode. The bottom electrode is arranged between the substrate and the piezoelectric layer, the piezoelectric layer is arranged between the bottom electrode and the top electrode, and a multilayer cavity is arranged between the bottom electrode and the substrate. The multilayer cavity has a width gradually decreased in a direction away from the substrate, so that the change in shapes of the bottom electrode and the piezoelectric layer subsequently arranged on the multilayer cavity at a boundary of each layer of the multilayer cavity is reduced, thus reducing the change in stress due to a large change in shape. A filter, an electronic device and a method for manufacturing a resonator are further provided.