Piezoelectric Resonator With Embedded Frame for High-Frequency Q
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Solution Overview
Problem
Existing piezoelectric thin film Bulk Acoustic Wave Resonators (BAWRs) face challenges at frequencies above 5 GHz due to reduced crystallinity, which affects their performance and quality factor.
Innovation Solution
The development of piezoelectric resonator devices with embedded energy confinement frames, utilizing a transfer process involving a sacrificial layer and epitaxial or single crystal piezoelectric films, enhances crystalline quality and electro-mechanical coupling for high-frequency applications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If piezoelectric thin films are used for BAWR applications, then devices can operate at frequencies from 1 to 3 GHz, but the crystallinity is reduced and performance deteriorates at frequencies around 5 GHz and above
Solution Approach 1:
The patent changes the crystalline structure parameter from polycrystalline to single crystal, and modifies the growth method parameters (temperature, pressure, composition control during epitaxial growth) to achieve high-quality single crystal piezoelectric films that maintain excellent crystallinity at high operating frequencies of 5 GHz and above
Solution Approach 2:
The patent employs composite material structures including single crystal piezoelectric films combined with specific substrate materials and electrode configurations, creating a multi-layer composite system that optimizes both high-frequency performance and crystalline quality
2Reliability
If standard piezoelectric thin film processes are used, then manufacturing is simpler, but acoustic wave control and quality factor are insufficient at high frequencies
Solution Approach 1:
The patent segments the fabrication process into distinct stages: substrate preparation, controlled epitaxial growth of single crystal piezoelectric layers, precise electrode deposition, and post-growth processing. This segmentation allows optimization of each stage independently to achieve high quality factor while managing overall process complexity
Solution Approach 2:
The patent introduces intermediate layers and buffer structures during the epitaxial growth process that facilitate controlled crystal growth and improve acoustic wave confinement, acting as intermediaries between the substrate and the piezoelectric film to enhance overall device performance
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 results in high-quality bulk acoustic wave resonators with improved performance and cost-efficiency, enabling superior acoustic wave control and increased quality factor at high frequencies.
Implementation Method 1
Bulk acoustic Wave Resonators (BAWR) incorporating piezoelectric thin films
Implementation Method 2
epitaxial or single crystal piezoelectric films
Data Source
AI summary
A piezoelectric resonator device can be formed to include a piezoelectric film including an active area configured to provide a thickness excited mode of vibration, a first electrode on a first surface of the piezoelectric film positioned to electromechanically couple to the active area, a second electrode on a second surface of the piezoelectric film, opposite the first surface, the second electrode positioned to electromechanically couple to the active area, an energy confinement frame extending on the piezoelectric film embedded in the first or second electrode, an inner side wall of the energy confinement frame facing toward the active area and extending around the active area to define a perimeter that separates the active area located inside the perimeter from an outer area located outside the perimeter adjacent to the active area, an outer side wall of the energy confinement frame facing toward the outer area and aligned to an outer side wall of the first or second electrode and a conformal low-impedance acoustic layer extending on the active area over the energy confinement frame to cover the outer side wall of the energy confinement frame, and onto the piezoelectric film in the outer area.