Bulk Acoustic Resonator Layer Stack for Frequency Sensitivity
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Solution Overview
Problem
Current bulk acoustic resonators face challenges in achieving high frequency sensitivity and robustness for applications in modern mobile devices, particularly in 5G communications, due to limitations in frequency control and chemical resistance, which affect their performance and reliability.
Innovation Solution
The design incorporates a substrate with a frequency control layer, a piezoelectric layer, electrodes, and a protective layer, where the frequency control layer covers a larger area than the protective layer, and includes materials like SiO2, Si3N4, and AlN, with specific thicknesses and material combinations to enhance frequency sensitivity and chemical resistance, and a metal layer with different materials for improved galvanic corrosion resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a frequency control layer is added to adjust resonant frequency, then frequency control capability is improved, but device structure becomes more complex
Solution Approach 1:
The frequency control function is segmented from the protective layer into a separate frequency control layer, allowing independent optimization of frequency control capability while maintaining protective functions in the protective layer. This segmentation enables precise frequency adjustment without compromising device protection.
Solution Approach 2:
The frequency control layer acts as an intermediary between the protective layer and the bulk acoustic resonator, providing frequency control capability while the protective layer maintains its protective function. This intermediary structure allows both functions to coexist without interference.
2Reliability
If protective layer thickness is increased to improve chemical resistance, then chemical resistance is improved, but frequency sensitivity deteriorates
Solution Approach 1:
The protective function and frequency control function are segmented into separate layers with different thickness optimizations. The protective layer can be thicker for chemical resistance without directly affecting frequency sensitivity, as the frequency control layer is specifically designed and positioned to control frequency characteristics.
Solution Approach 2:
Different layers are assigned different local qualities: the protective layer is optimized for chemical resistance with appropriate thickness and material properties, while the frequency control layer is optimized for frequency control with specific thickness and material characteristics. This local quality differentiation allows both requirements to be satisfied simultaneously.
3Measurement precision
If frequency control layer covers larger area than protective layer, then frequency sensitivity is improved, but device structure becomes more complex
Solution Approach 1:
The frequency control layer is designed with an asymmetric area configuration, covering a larger area than the protective layer. This asymmetric design allows the frequency control layer to effectively control the resonant frequency of the bulk acoustic resonator while the protective layer maintains its protective function in a smaller area.
4Reliability
If metal layer is added for galvanic corrosion resistance, then reliability is improved, but device complexity increases
Solution Approach 1:
The metal layer serves as an intermediary between the protective layer and the underlying structures, providing galvanic corrosion resistance. This intermediary layer protects against galvanic corrosion while allowing the protective layer to maintain its protective function without direct contact with potentially corrosive environments.
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 configuration improves the frequency sensitivity and chemical resistance of bulk acoustic resonators, leading to enhanced performance and reliability, particularly in high-frequency applications like 5G communications, by reducing notch and spurious effects and increasing trim uniformity.
Implementation Method 1
a piezoelectric layer disposed between the frequency control layer and the substrate
Implementation Method 2
a frequency control layer changing a resonant frequency or antiresonant frequency of the bulk acoustic resonator according to a thickness of the frequency control layer
Data Source
AI summary
A bulk acoustic resonator includes a substrate, a frequency control layer changing a resonant frequency or antiresonant frequency of the bulk acoustic resonator according to a thickness of the frequency control layer, a piezoelectric layer disposed between the frequency control layer and the substrate, a first electrode disposed between the piezoelectric layer and the substrate, a second electrode disposed between the piezoelectric layer and the frequency control layer, a metal layer connected to the first electrode or the second electrode, and a protective layer disposed between the second electrode and the frequency control layer, wherein the frequency control layer covers a larger area than that of the protective layer.