Bulk Acoustic Wave Resonator Electrode Layout for Temperature Stability
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Solution Overview
Problem
Conventional bulk acoustic wave devices face challenges with temperature compensation layers that are difficult to manufacture thinly, leading to limited temperature compensation effects and degradation of coupling coefficients, especially when positioned between electrodes and piezoelectric layers.
Innovation Solution
The proposed solution involves separating the temperature compensation layer from the piezoelectric layer by positioning it between layers of the second electrode, thereby reducing electric field exposure and allowing for a thicker layer, which enhances manufacturing feasibility and improves temperature coefficient of frequency and coupling coefficient k2.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the temperature compensation layer is positioned between the electrode and the piezoelectric layer, then temperature compensation effect is improved, but the coupling coefficient is degraded and manufacturing becomes difficult
Solution Approach 1:
The temperature compensation layer is repositioned from the traditional location between the electrode and piezoelectric layer to a new dimension within the electrode structure itself (between the first and second layers of the second electrode). This spatial reconfiguration allows the layer to maintain its temperature compensation function while avoiding the manufacturing challenges and coupling coefficient degradation associated with positioning it directly against the piezoelectric layer.
2Ease of manufacture
If the temperature compensation layer is made thinner, then coupling coefficient is improved, but temperature compensation effect is limited
Solution Approach 1:
The first layer of the second electrode serves as an intermediary between the temperature compensation layer and the piezoelectric layer. This intermediate structure allows the temperature compensation layer to be made thicker (improving temperature compensation) while the first layer maintains the necessary electrical coupling and acoustic performance, effectively mediating between the conflicting requirements.
3Stability of the object's composition
If the temperature compensation layer is positioned between electrodes and piezoelectric layers, then temperature stability is improved, but electric field exposure degrades coupling coefficient
Solution Approach 1:
The second electrode is segmented into multiple layers (first layer and second layer), with the temperature compensation layer positioned between them. This segmentation allows the temperature compensation layer to be shielded from direct exposure to the full electric field by the first layer, while still maintaining temperature stability benefits. The segmented structure effectively reduces electric field exposure to the temperature compensation layer.
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 results in improved temperature stability and coupling efficiency, with a temperature coefficient closer to zero and higher coupling coefficients, while maintaining acoustic performance.
Implementation Method 1
A bulk acoustic wave resonator can include a set of metal electrodes deposited on opposite surfaces of a piezoelectric material, generating a bulk acoustic wave within the volume of the piezoelectric material. The interaction between the electrodes and the piezoelectric material results in the formation and propagation of a bulk acoustic wave.
Implementation Method 2
a temperature compensation layer between the first and second layers of the second electrode
Data Source
AI summary
A bulk acoustic wave device is disclosed. The bulk acoustic wave device can include a first electrode, a second electrode including a first layer and a second layer, a piezoelectric layer between the first and second electrodes, and a temperature compensation layer between the first and second layers of the second electrode.