Gradient-Doped Piezoelectric Structure for Resonator Coupling Trade-Off
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Solution Overview
Problem
Piezoelectric resonators face a challenge in achieving a good trade-off between electromechanical coupling coefficient and quality factor, as high values of one often contradict the other, affecting the performance of filters in wireless communication devices.
Innovation Solution
A piezoelectric structure with a doping element concentration varying along its thickness direction, optimizing the electromechanical coupling coefficient and quality factor through a combination of first and second doping elements, such as Ti and B, to regulate the coupling coefficient and improve the figure of merit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the electromechanical coupling coefficient is increased to improve bandwidth, then the quality factor decreases due to increased edge energy loss
Solution Approach 1:
The patent applies local quality by creating a non-uniform doping concentration distribution within the piezoelectric layer. The doping concentration varies along the thickness direction, with different concentrations at different positions, allowing the electromechanical coupling coefficient to be optimized in the bulk while minimizing edge energy loss at the surfaces. This spatial variation in material properties resolves the contradiction between coupling coefficient and quality factor.
Solution Approach 2:
The patent changes the physical parameter of doping concentration along the thickness direction of the piezoelectric layer. By continuously or discontinuously varying the doping concentration from the center toward the edges, the electromechanical coupling coefficient is modulated to achieve optimal values throughout the layer, thereby improving the figure of merit without sacrificing quality factor.
2Ease of manufacture
If a uniform doping concentration is used throughout the piezoelectric layer, then the manufacturing process is simple, but the electromechanical coupling coefficient cannot be optimized along the thickness direction
Solution Approach 1:
Instead of uniform doping, the patent implements local quality variations by controlling doping concentration to differ at various positions along the thickness direction. This can be achieved through sequential doping processes or gradient doping techniques, where different doping levels are applied to different regions, optimizing the electromechanical coupling coefficient while maintaining manufacturing feasibility.
Solution Approach 2:
The patent employs preliminary action by pre-designing the doping concentration profile before manufacturing. The doping concentration distribution is planned and implemented in advance to achieve the desired electromechanical coupling coefficient variation, allowing optimization of device performance before final assembly and testing.
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 enables the manufacture of piezoelectric resonators with enhanced figure of merit, supporting high-frequency band and large bandwidth communication, while minimizing edge energy leakage and mechanical loss.
Implementation Method 1
Piezoelectric materials (ceramics, thin films, and crystals) have excellent capabilities of electromechanical conversion, and therefore are widely used in various fields, especially in the field of microelectronic devices and electronic devices. Mechanical resonance characteristics inherent to such piezoelectric materials help to realize conversion between acoustic signals (sound waves) and electrical signals.
Implementation Method 2
a piezoelectric layer doped with a first doping element at a first doping concentration. The first doping concentration varies along a thickness direction of the piezoelectric layer with at least two change rates. An electromechanical coupling coefficient of the piezoelectric layer varies along the thickness direction of the piezoelectric layer.
Data Source
AI summary
The present disclosure relates to a piezoelectric structure with an optimized electromechanical coupling coefficient, a method for manufacturing the piezoelectric structure, and a piezoelectric resonator including the piezoelectric structure. The piezoelectric structure according to the present disclosure may include a piezoelectric layer doped with a first doping element at a first doping concentration. The first doping concentration varies along a thickness direction of the piezoelectric layer with at least two change rates. An electromechanical coupling coefficient of the piezoelectric layer continuously varies along the thickness direction of the piezoelectric layer. According to the present disclosure, a piezoelectric structure with an electromechanical coupling coefficient varying continuously and/or cyclically along a thickness direction of a piezoelectric layer may be obtained without significant increase of extra process cost, and a figure of merit of a piezoelectric resonator including the piezoelectric structure is finally improved.