HBAR Oscillator Structure With FBAR Isolation for Higher Q-Factor
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Solution Overview
Problem
High tone bulk acoustic resonators (HBARs) face challenges due to high acoustic loss in substrates, which affects their quality factor, and existing materials are difficult to process in large-scale fabrication, leading to adverse impacts on device performance.
Innovation Solution
A method involving a substrate with a selected thickness for a high tone bulk acoustic resonator (HBAR) combined with a film bulk acoustic resonator (FBAR) filter and acoustic isolators, using materials like single-crystal silicon and piezoelectric layers to optimize acoustic attenuation and reduce substrate thickness, thereby improving the Q-factor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a substrate material with low acoustic loss is used to improve the Q-factor of HBAR, then the quality factor is improved, but the material becomes difficult to process in large-scale fabrication
Solution Approach 1:
The patent changes the thickness parameter of the substrate to resolve the contradiction. By reducing the substrate thickness to a specific range (5-50 micrometers), the acoustic loss is reduced thereby improving the Q-factor, while still maintaining compatibility with standard fabrication processes. This parameter optimization allows achieving high performance without sacrificing manufacturability
Solution Approach 2:
The patent transitions from considering only material selection to incorporating thickness as a critical dimension. By controlling the substrate thickness in the micrometer range, the invention adds a dimensional parameter that simultaneously addresses both acoustic loss reduction and fabrication compatibility, resolving the contradiction between performance and manufacturability
2Reliability
If the substrate thickness is reduced to improve acoustic loss and Q-factor, then the quality factor is improved, but the mechanical strength and robustness of the device may be compromised
Solution Approach 1:
The patent optimizes the substrate thickness parameter to a specific range (5-50 micrometers) that balances acoustic performance and mechanical strength. This parameter selection reduces acoustic loss for improved Q-factor while maintaining sufficient mechanical robustness for handling and integration in wireless devices
Solution Approach 2:
The patent employs composite structures including piezoelectric layers, electrode layers, and acoustic isolation layers combined with the substrate. These composite materials and structures provide both the acoustic performance needed for high Q-factor and the mechanical strength required for device robustness, compensating for the reduced substrate thickness
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 approach enhances the quality factor of HBARs by reducing acoustic losses and facilitating processing, allowing for improved performance in wireless communications devices with reduced power consumption and increased robustness.
Implementation Method 1
The HBAR comprises a piezoelectric transducer disposed over a support substrate. In general, the piezoelectric transducer includes a piezoelectric layer disposed between metal electrode layers.
Implementation Method 2
the HBAR exhibits multiple resonances that are equally spaced, with the spacing being determined by the thickness of the substrate
Implementation Method 3
most of the acoustic energy of the HBAR is stored in the substrate
Implementation Method 4
the Q-factor of the HBAR is dominated by acoustic loss (e.g., attenuation) in the substrate
Data Source
AI summary
An oscillator comprises a substrate and a high tone bulk acoustic resonator (HBAR), which includes a portion of the substrate. The oscillator also comprises a film bulk acoustic resonator (FBAR) filter disposed over the substrate. The filter comprises a plurality of FBAR devices. The oscillator also comprises a plurality of acoustic isolators disposed in the substrate, wherein one of the isolators is disposed beneath each of the FBAR devices. A method of fabricating an oscillator is also disclosed.