BAW Resonator Piezoelectric Film Polarity Patterning for Spurious Mode Control
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Solution Overview
Problem
Existing BAW resonators face challenges in achieving optimal performance due to spurious modes and limited flexibility in electromechanical coupling, which affects filter design and size, particularly in high-frequency communication applications.
Innovation Solution
A piezoelectric film with polarity-patterned non-piezoelectric portions, comprising pillars and a mesh with opposite polar orientations, is integrated into the BAW resonator structure to control electromechanical coupling, allowing for varying coupling coefficients in different regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a uniform piezoelectric film is used in BAW resonators, then the structure is simple and easy to manufacture, but the electromechanical coupling is limited and spurious modes occur
Solution Approach 1:
The piezoelectric film is divided into regions with different polar orientations (first polar orientation in certain areas, second polar orientation in other areas). This local differentiation allows specific regions to have enhanced electromechanical coupling or suppressed spurious modes, while maintaining overall structural simplicity and manufacturability through a relatively straightforward fabrication process.
2Reliability
If the piezoelectric film is polarity patterned to reduce spurious modes and control coupling, then filter performance improves, but the manufacturing process becomes more complex
Solution Approach 1:
The piezoelectric film is segmented into distinct polar regions (first polar orientation and second polar orientation) to control electromechanical coupling and suppress spurious modes. This segmentation is achieved through a fabrication process that deposits piezoelectric material over metal islands, allowing different polar orientations in different areas while managing complexity through systematic processing steps.
3Manufacturing precision
If metal islands are self-assembled to define polarity regions, then manufacturing precision is improved, but the process requires additional control parameters
Solution Approach 1:
Metal islands are formed through self-assembly processes where the piezoelectric material spontaneously organizes around metal nuclei or islands during deposition. This self-service mechanism defines polarity regions with high precision without requiring complex external patterning steps, as the system naturally forms the desired structure through thermodynamic or kinetic driving forces inherent in the deposition process.
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 approach enhances the BAW resonator's performance by reducing spurious modes and enabling tailored electromechanical coupling, improving filter characteristics and reducing size, suitable for high-frequency communication devices.
Implementation Method 1
A piezoelectric film resides over the foundation structure and is formed from a piezoelectric material. The piezoelectric film has a non-piezoelectric portion over the first area and a piezoelectric portion over a second area of the top surface of the foundation structure.
Data Source
AI summary
This disclosure relates generally to a method of making a piezoelectric device. In some embodiments, a foundation structure is provided and a first metal is deposited over at least a first area of a top surface of the foundation structure to form a plurality of metal islands such that the plurality of metal islands self-assemble in a distributed manner over the at least the first area of the top surface of the foundation structure. Additionally, a piezoelectric material is deposited over the at least the first area of the top surface of the foundation structure to form a piezoelectric film over the at least the first area of the top surface of the foundation structure. The piezoelectric material is deposited over the first area of the top surface of the foundation structure to form the piezoelectric film and the piezoelectric film is polarity patterned into at least one non-piezoelectric portion.