Single-Crystal BAW Structure for High-Q Acoustic Resonance
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Solution Overview
Problem
The existing bulk acoustic wave (BAW) structures face challenges in achieving high Q values due to the difficulty in growing single crystal piezoelectric material layers, which affects the reliability of BAW filters, especially in portable electronic products where strict frequency specifications are required.
Innovation Solution
A BAW structure with a single crystal piezoelectric material layer, where the second electrode covers the entire surface of the layer and an acoustic reflector is disposed on one of the electrodes, is used, along with a manufacturing method involving a single crystal substrate and subsequent electrode formation to ensure direct contact and improved Q values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional manufacturing processes are used to form the piezoelectric material layer, then the manufacturing process is simpler, but the piezoelectric material layer cannot grow into a single crystal material, resulting in reduced Q value and affecting product reliability
Solution Approach 1:
The patent applies preliminary action by providing a single crystal substrate before forming the piezoelectric material layer. This pre-prepared substrate enables the piezoelectric layer to grow as a single crystal during the manufacturing process, thereby achieving high Q value without significantly complicating the overall manufacturing process. The single crystal substrate serves as a foundation that guides the crystal growth of the piezoelectric material layer.
2Reliability
If the second electrode area is increased to cover the entire surface of the piezoelectric material layer, then the electrical contact is improved, but the device size increases
Solution Approach 1:
The patent applies partial action by making the second electrode area equal to or slightly larger than the piezoelectric material layer area, rather than extending it unnecessarily far beyond the layer. This ensures complete electrical contact with the piezoelectric material for reliable electrical connection, while avoiding excessive electrode extension that would increase the overall device area. The electrode size is optimized to be just sufficient for complete contact.
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 enhances the Q value of the BAW structure, enabling more reliable and miniaturized BAW devices suitable for portable electronics, while allowing for flexible frequency applications by using BAW structures with different filtering effects.
Implementation Method 1
When an electric field is applied to the metal electrodes, the piezoelectric material layer generates an acoustic wave due to vibration
Implementation Method 2
the acoustic wave oscillates in the piezoelectric material layer to form a standing wave, so as to reduce energy loss
Implementation Method 3
an acoustic reflector is disposed on a surface of the first electrode
Data Source
AI summary
A bulk acoustic wave (BAW) structure includes a single crystal piezoelectric material layer, a first electrode, a second electrode and an acoustic reflector. The first and second electrodes are respectively located on a first surface and a second surface of the single crystal piezoelectric material layer. The area of the second electrode is greater than or equal to that of the second surface of the single crystal piezoelectric material layer, and the contact area of the single crystal piezoelectric material layer with the second electrode is equal to the area of the second surface of the single crystal piezoelectric material layer. The acoustic reflector is disposed on a surface of the first electrode.