Piezoelectric Membrane Structure for Horizontal Polarization Alignment
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Solution Overview
Problem
Existing membrane structures with piezoelectric films oriented perpendicular to the substrate face challenges in aligning polarization directions other than perpendicular, which limits permittivity and withstand voltage characteristics, necessitating a solution to achieve horizontal polarization alignment.
Innovation Solution
A membrane structure comprising a Si or SOI substrate with a ZrO2 buffer film and a piezoelectric film, such as AlN, where the polarization direction is preferentially oriented parallel to the substrate, and optionally includes metal films like Pt or Mo, and SRO layers, with electrodes and a hollow structure to enhance acoustic wave generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the piezoelectric film is made with c-axis orientation perpendicular to the substrate, then it is easy to align the polarization direction perpendicular to the substrate, but the polarization direction cannot be aligned horizontally to improve permittivity and withstand voltage characteristics
Solution Approach 1:
The invention changes the crystal orientation parameter of the piezoelectric film from c-axis perpendicular orientation to a-axis horizontal orientation. This parameter change enables the polarization direction to be aligned horizontally parallel to the substrate surface, which improves permittivity and withstand voltage characteristics while maintaining manufacturability through controlled film deposition processes
Solution Approach 2:
The invention uses a composite structure consisting of a piezoelectric film layer and a buffer layer with specific crystal orientations. The buffer layer is configured to induce a-axis orientation in the piezoelectric film, creating a composite material system that achieves horizontal polarization alignment and enhanced electrical characteristics
2Ease of manufacture
If the piezoelectric film is made with c-axis orientation perpendicular to the substrate, then the polarization direction aligns perpendicular to the substrate, but the withstand voltage characteristics are limited
Solution Approach 1:
The invention changes the crystal orientation parameter from c-axis to a-axis orientation, which fundamentally alters the polarization direction from perpendicular to horizontal alignment. This parameter change simultaneously improves both the control of polarization direction and the withstand voltage characteristics by utilizing the anisotropic properties of the piezoelectric material in different crystal directions
3Device complexity
If the piezoelectric film is made with c-axis orientation perpendicular to the substrate, then the structure is simple to fabricate, but the permittivity characteristics are suboptimal
Solution Approach 1:
The invention modifies the crystal orientation parameter to achieve a-axis horizontal orientation, which improves permittivity characteristics. The fabrication complexity is managed through established thin-film deposition techniques that can control crystal orientation, balancing device performance with manufacturing feasibility
Solution Approach 2:
The invention introduces a buffer layer as an intermediary between the substrate and the piezoelectric film. This buffer layer serves as a mediator that induces and controls the a-axis orientation of the piezoelectric film, enabling horizontal polarization alignment and improved permittivity characteristics while maintaining a manageable fabrication 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 configuration allows for improved permittivity and withstand voltage characteristics by aligning the polarization direction horizontally, enabling efficient bulk and surface acoustic wave generation in electronic devices.
Implementation Method 1
a piezoelectric film formed on the buffer film, a polarization direction in the piezoelectric film being preferentially oriented parallel to the substrate
Data Source
AI summary
A membrane structure (10) includes: a substrate being a Si substrate or an SOI substrate; a buffer film containing ZrO2 and formed on the substrate; and a piezoelectric film (11) formed on the buffer film, a polarization direction in the piezoelectric film (11) being preferentially oriented parallel to the substrate.