LiTaO3 Piezoelectric Bulk Wave Device with Optimized Euler Angles
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Solution Overview
Problem
Piezoelectric thin film devices using LiTaO3 struggle to achieve a high electromechanical coupling coefficient k2 for thickness shear mode, limiting their ability to provide a wide frequency band or adjustable range of band width.
Innovation Solution
A piezoelectric bulk wave device utilizing a LiTaO3 thin plate with specific Euler Angles (φ, θ, φ) where φ is 0° and θ is between 54° and 107°, combined with ion implantation techniques to form high concentration ion-implanted portions, allowing for precise thickness control and reduced thermal stress, thereby enhancing the electromechanical coupling coefficient k2.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a piezoelectric thin film device uses thickness shear mode of LiTaO3, then the device structure is simple and easy to manufacture, but the electromechanical coupling coefficient k2 cannot be made sufficiently high
Solution Approach 1:
The patent changes the Euler angle parameters of the LiTaO3 crystal, specifically setting φ to 0° and θ to between 54° and 107°, to achieve a high electromechanical coupling coefficient k2 of 12% or more while maintaining the thickness shear mode configuration
Solution Approach 2:
The patent performs preliminary ion implantation to create a high concentration ion-implanted portion before device fabrication, which enables precise thickness control and reduces thermal stress during subsequent manufacturing processes
2Adaptability or versatility
If the electromechanical coupling coefficient k2 is increased to achieve wider frequency band, then the frequency band width increases, but spurious modes and temperature coefficient of frequency increase
Solution Approach 1:
The patent optimizes the Euler angle parameters (φ=0°, θ=54°-107°) to achieve a balance where the electromechanical coupling coefficient k2 is high (12% or more) while the electromechanical coupling coefficient of the spurious thickness longitudinal vibration mode is suppressed to 3% or less
Solution Approach 2:
The patent creates a high concentration ion-implanted portion at a specific depth from the surface to achieve local thickness control, which reduces thermal stress and minimizes spurious modes while maintaining the desired frequency characteristics
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
The solution enables a piezoelectric bulk wave device with increased electromechanical coupling coefficient k2, resulting in a wider band width and improved frequency stability, while minimizing spurious modes and temperature coefficient of frequency.
Implementation Method 1
a piezoelectric bulk wave device that utilizes a bulk wave of thickness shear mode as a bulk wave
Implementation Method 2
ion implantation techniques to form high concentration ion-implanted portions
Data Source
AI summary
A piezoelectric bulk wave device that includes a piezoelectric thin plate that is made of LiTaO3, and first and second electrodes that are provided in contact with the piezoelectric thin plate. The piezoelectric bulk wave device utilizes the thickness shear mode of the piezoelectric thin plate made of LiTaO3, and of the Euler Angles (φ, θ, φ) of LiTaO3, φ is 0°, and θ is in the range of not less than 54° and not more than 107°.