BAW Resonator Thick Electrodes for Q Factor and Alignment Stability
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Solution Overview
Problem
Conventional RF technologies face limitations in achieving high performance bulk acoustic wave resonators for frequencies above 5 GHz due to the degradation of polycrystalline piezoelectric films, and challenges in manufacturing single crystal piezoelectric thin films for improved resonator devices.
Innovation Solution
An anti-symmetrical configuration for bulk acoustic wave resonator devices with partial mass-loaded structures on both electrodes, using materials like molybdenum, ruthenium, and aluminum-copper, to achieve a symmetric acoustic impedance profile and lower electrical resistance, enhancing the Q factor and compatibility with arbitrary resonator shapes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If polycrystalline piezoelectric thin films are used for BAW resonators, then manufacturing is easier and costs are lower, but the quality degrades quickly as thickness decreases below 0.5 um, limiting operation to frequencies up to 3 GHz
Solution Approach 1:
The patent changes the crystalline structure parameter of the piezoelectric film from polycrystalline to single crystal, and adjusts the thickness parameter to very thin dimensions (0.4 um or less), enabling operation at frequencies of 5 GHz and above while maintaining high film quality
2Reliability
If single crystal piezoelectric thin films are used for improved crystalline quality and high piezoelectric performance at very thin thicknesses, then resonator performance improves for frequencies around 5 GHz and above, but challenges arise in manufacturing and transferring these films
Solution Approach 1:
The patent introduces a transfer substrate as an intermediate carrier, enabling the single crystal piezoelectric film to be grown on a compatible substrate and then transferred to the final BAW resonator device, thus solving the manufacturing challenge of handling very thin single crystal films
3Adaptability or versatility
If conventional RF technology is used, then current applications are supported, but limitations exist that are problematic for future high-frequency requirements and may lead to drawbacks
Solution Approach 1:
The patent changes the operating frequency parameter to 5 GHz and above by using single crystal piezoelectric films with superior crystalline quality and high piezoelectric performance, enabling future high-frequency applications while maintaining compatibility with conventional RF technology architectures
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 anti-symmetrical configuration improves the Q factor by reducing misalignment issues and achieving lower electrical resistance, while being compatible with conventional manufacturing methods and materials, thus addressing the limitations of existing technologies for high-frequency resonators.
Implementation Method 1
a piezoelectric layer (220) formed overlying a substrate member (210). A front-side electrode (230) is formed overlying the piezoelectric layer (220), while a back-side electrode (240) is formed underlying the piezoelectric layer (220)
Data Source
AI summary
A resonator circuit device. This device can include a piezoelectric layer having a front-side electrode and a back-side electrode spatially configured on opposite sides of the piezoelectric layer. Each electrode has a connection region and a resonator region. Each electrode also includes a partial mass-loaded structure configured within a vicinity of its connection region. The front-side electrode and the back-side electrode are spatially configured in an anti-symmetrical manner with the resonator regions of both electrodes at least partially overlapping and the first and second connection regions on opposing sides. This configuration provides a symmetric acoustic impedance profile for improved Q factor and can reduce the issues of misalignment or unbalanced boundary conditions associated with conventional single mass-loaded perimeter configurations.