Bulk Acoustic Wave Sensor Delay Layer for Higher Q Resonance
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Solution Overview
Problem
Conventional bulk acoustic wave sensors face challenges in achieving high quality-factor resonators due to the difficulty and expense of manufacturing uniformly thick substrates required for delay layers, which affects their sensitivity and accuracy in mass sensing applications.
Innovation Solution
A bulk acoustic wave sensor design incorporating an overmoded resonating structure with a delay layer of high Q factor material placed adjacent to the base resonator, either between the electrodes or on top, enhancing the Q factor and allowing for flexible trade-offs between quality factor and coupling efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional bulk acoustic wave sensor uses a substrate as the delay layer, then the Q factor can be improved, but the manufacturing precision and cost increase due to the requirement of very uniform substrate thickness
Solution Approach 1:
The delay layer is segmented from the substrate and implemented as a separate thin-film layer deposited on the substrate. This allows the delay layer to be manufactured independently with standard thin-film deposition techniques, eliminating the need for the entire substrate to have uniform thickness. The delay layer can be precisely controlled in thickness while the substrate serves only as a mechanical support.
Solution Approach 2:
An acoustic mirror layer is introduced as an intermediary between the substrate and the delay layer. This acoustic mirror reflects acoustic waves back into the delay layer, enabling the delay layer to function effectively even when it is not directly attached to the substrate. This mediator allows the system to achieve high Q factor without requiring uniform substrate thickness.
2Reliability
If the substrate is used for the delay layer, then the Q factor is enhanced, but the device complexity and manufacturing cost increase
Solution Approach 1:
The delay layer is segmented from the substrate and implemented as a separate thin-film layer deposited on the substrate. This allows the delay layer to be manufactured independently with standard thin-film deposition techniques, eliminating the need for the entire substrate to have uniform thickness. The delay layer can be precisely controlled in thickness while the substrate serves only as a mechanical support.
Solution Approach 2:
The invention changes the manufacturing parameters from requiring uniform substrate thickness to using standard thin-film deposition parameters. The delay layer thickness is controlled through deposition process parameters (time, temperature, pressure) rather than substrate machining parameters, which are typically more expensive and less precise.
3Measurement precision
If a delay layer is added to enhance Q factor, then the sensing capability is improved, but the device structure becomes more complex
Solution Approach 1:
The acoustic mirror layer serves multiple functions: it reflects acoustic waves to enhance the Q factor of the delay layer, provides a defined boundary for the resonating structure, and can be integrated with the electrode structure. This multi-functionality reduces the need for additional components and simplifies the overall device structure despite the added functionality.
Solution Approach 2:
The delay layer and acoustic mirror layer are nested within the existing resonator structure, with the delay layer positioned between the substrate and the base resonator. This nested configuration allows the Q-enhancing elements to be integrated into the existing device footprint without requiring additional lateral space or complex external components.
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 proposed design boosts the Q factor of the resonator, improving sensing capabilities, particularly for sensitive applications, while being fabricated using standard thin-film deposition techniques, eliminating the need for precise substrate thickness control.
Implementation Method 1
a base resonator having a piezoelectric layer, a first electrode disposed on a first surface of the piezoelectric layer, a second electrode disposed on a second surface of the piezoelectric layer
Implementation Method 2
a delay layer disposed between a bottom electrode and an acoustic mirror, a delay layer disposed on a top electrode, or both. The one or more delay layers may be formed of high Q factor material
Implementation Method 3
an acoustic mirror layer adjacent to the base resonator or the acoustic delay layer
Data Source
AI summary
A bulk acoustic wave sensor includes a delay layer. The sensor includes an acoustic mirror and a base resonator. The base resonator includes a piezoelectric layer and two electrodes. One or more delay layers are disposed adjacent to the base resonator. A delay layer may be disposed between the base resonator and the acoustic mirror, a delay layer may be disposed on the base resonator opposite to the acoustic mirror, or both. Each delay section is formed of high quality-factor material. The sensor may define a resonant frequency, and the thickness of each delay section may be an integer multiple of half-wavelengths of the resonant frequency.