Bulk Acoustic Resonator Cavity Structure Without Release Holes
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Solution Overview
Problem
Conventional bulk acoustic resonator manufacturing processes damage the stress uniformity of the piezoelectric layer due to the creation of release holes, leading to weakened resonator performance.
Innovation Solution
A cavity structure for bulk acoustic resonators featuring criss-crossed release channels around the resonators, which allows for the release of sacrificial material without damaging the piezoelectric layer, and a manufacturing process that includes forming a support layer with a release channel and groove to facilitate stress uniformity and efficient release.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a release hole is manufactured on the electrode layer and piezoelectric layer to release the sacrificial layer, then the cavity can be released, but the stress uniformity of the piezoelectric layer is damaged
Solution Approach 1:
The patent transitions from vertical release holes (through the piezoelectric layer) to lateral release channels (in the support layer), changing the dimensional approach to cavity release. This allows sacrificial material removal without penetrating the piezoelectric layer, preserving stress uniformity while achieving cavity release.
Solution Approach 2:
The support layer acts as an intermediary structure that contains the release channels. By routing release paths through the support layer rather than directly through the piezoelectric layer, the patent mediates between the need for cavity release and the requirement to maintain piezoelectric layer integrity.
2Ease of manufacture
If a release hole is manufactured in the periphery of the inner side of the cavity, then the cavity can be released, but the peripheral piezoelectric layer structure is damaged
Solution Approach 1:
The support layer serves as a protective intermediary that houses the release channels. This allows cavity release functionality to be implemented without the release paths intersecting or damaging the peripheral piezoelectric layer structure.
Solution Approach 2:
The patent segments the release function from the piezoelectric layer by placing release channels exclusively in the support layer. This separation ensures that cavity release operations do not compromise the integrity of the piezoelectric layer structure.
3Strength
If SiN is used as the support layer material, then structural support is provided, but high selection ratio materials are required for the sacrificial layer and wet release process damages the piezoelectric layer
Solution Approach 1:
The support layer with lateral release channels acts as an intermediary system that enables alternative release methodologies. By providing dedicated release pathways in the support layer, the patent facilitates the use of release methods that do not require aggressive wet etching that would damage the piezoelectric layer.
Solution Approach 2:
The patent changes the release approach parameters by using lateral channels in the support layer rather than vertical holes through the piezoelectric layer. This parameter change enables milder release processes that are less harmful to the piezoelectric layer while maintaining effective cavity release.
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 maintains stress uniformity of the piezoelectric layer, enhancing resonator performance by eliminating the need for release holes and simplifying the manufacturing process, thereby improving the efficiency and stability of the resonator.
Implementation Method 1
The piezoelectric layer can realize the conversion of electrical energy and mechanical energy. When an electric field is applied to the upper and lower electrodes, the piezoelectric layer converts the electrical energy into the mechanical energy, which macroscopically exists in a form of sound waves.
Implementation Method 2
The oscillated sound waves excite radio frequency signals, and thus the mechanical energy is converted into the electrical energy.
Data Source
AI summary
A cavity structure of a bulk acoustic resonator and a manufacturing process. The cavity structure comprises a substrate and a cavity formed on the substrate, a support layer is arranged on the substrate to form the cavity in a surrounding manner, a release channel in communication with the cavity is formed above the substrate in a same layer with the cavity, and the release channel extends, in parallel to the substrate, in a peripheral area of the cavity. There is no need to manufacture a release hole, which simplifies the manufacturing process of the resonator, thereby avoiding weakening the performance of the resonator due to damage to the structure of the piezoelectric layer around the electrode layer when manufacturing the release hole.