Common Glass Substrate Acoustic Wave Resonators With Spinel BAW
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Solution Overview
Problem
Current bulk acoustic wave resonators face challenges in achieving high-quality factor (Q) values and maintaining RF performance due to issues like energy leakage and mobilized electrons at the oxide-silicon interface, which affect their characteristics and manufacturing processes.
Innovation Solution
The use of a spinel substrate, such as a polycrystalline magnesium aluminate, for bulk acoustic wave resonators, which reduces tangent loss, enhances mechanical strength, and simplifies processing by forming a sacrificial layer directly over the substrate, thereby minimizing etching and eliminating mobilized electrons and holes, and allowing for better RF characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If high-resistivity silicon substrates are used for bulk acoustic wave resonators, then manufacturing process complexity is reduced, but substrate resistivity decreases and quality factor values deteriorate due to mobilized electrons and holes at the oxide-silicon interface
Solution Approach 1:
The patent changes the substrate material parameter from silicon to spinel (magnesium aluminate), which fundamentally alters the electrical properties at the interface. This material substitution eliminates the mobilization of electrons and holes that occurs at oxide-silicon interfaces, thereby maintaining high substrate resistivity and achieving superior quality factor values while remaining manufacturable
Solution Approach 2:
The patent employs a sacrificial layer approach where a temporary layer is deposited on the spinel substrate, patterned, and then removed to create the desired resonator structure. This copying methodology simplifies the manufacturing process by enabling standard photolithography and etching techniques to be used on the spinel substrate
2Reliability
If spinel substrates are used for bulk acoustic wave resonators, then quality factor values and mechanical strength are improved, but manufacturing process complexity increases due to additional processing steps
Solution Approach 1:
The patent applies preliminary action by depositing a sacrificial layer directly onto the spinel substrate before proceeding with resonator fabrication. This pre-deposited layer serves as a template that guides subsequent patterning and etching steps, simplifying the overall manufacturing process despite the novel substrate material
Solution Approach 2:
The sacrificial layer acts as an intermediary element between the spinel substrate and the final resonator structure. It enables the transfer of patterns from photomasks to the substrate through standard fabrication techniques, bridging the gap between the novel spinel material and conventional manufacturing processes
3Ease of manufacture
If oxide-silicon interfaces are used in bulk acoustic wave resonators, then manufacturing is simplified, but energy loss increases due to mobilized electrons and holes affecting RF performance
Solution Approach 1:
The patent changes the interface material parameter by replacing silicon with spinel substrate. This fundamental material substitution eliminates the formation of oxide-silicon interfaces and the associated mobilization of electrons and holes, thereby reducing energy loss and achieving lower tangent loss values while maintaining manufacturing feasibility
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 spinel substrate-based bulk acoustic wave resonators exhibit improved RF performance, mechanical strength, and reduced substrate resistivity, enabling better processability and quality factor values compared to high-resistivity silicon substrates, while allowing for the implementation of both BAW and SAW resonators on a common substrate.
Implementation Method 1
The ceramic substrate is a polycrystalline ceramic substrate
Implementation Method 2
Acoustic waves propagate in a bulk of a piezoelectric layer
Implementation Method 3
a SAW filter can include an interdigital transductor electrode on a piezoelectric substrate and can generate a surface acoustic wave on a surface of the piezoelectric layer
Data Source
AI summary
An acoustic wave component is disclosed. The acoustic wave component can include a bulk acoustic wave resonator and a surface acoustic wave device. The bulk acoustic wave resonator can include a first portion of a glass substrate, a first piezoelectric layer positioned on the glass substrate, and electrodes positioned on opposing sides of the first piezoelectric layer. The surface acoustic wave device can include a second portion of the glass substrate, a second piezoelectric layer positioned on the glass substrate, and an interdigital transducer electrode on the second piezoelectric layer.