SAW Reflective Structure for Compact High-Temperature Resonators
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Solution Overview
Problem
Current surface acoustic wave (SAW) devices face challenges in achieving high reflectivity and compact design, especially for high-temperature applications, as existing materials like Pt, Ta, W, and Mo suffer from deteriorating reflectivity and material property changes at elevated temperatures, and metals like Mo are difficult to handle industrially.
Innovation Solution
The design incorporates interdigitated transducers and acoustic wave reflective structures with different materials and geometrical parameters, allowing for optimized electro-mechanical coupling, quality factor, and temperature stability, using metals like Pt, W, Mo, or dielectric materials to enhance reflectivity and reduce the number of strips, thereby creating a more compact and stable SAW device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional metallic materials (Pt, Ta, W, Mo) are used for Bragg reflectors, then high reflectivity can be achieved, but the device size becomes large and the materials deteriorate at high temperatures
Solution Approach 1:
The patent changes the material parameter from traditional metals (Pt, Ta, W, Mo) to alternative materials such as tungsten disulfide (WS2), molybdenum disulfide (MoS2), and other transition metal dichalcogenides. These materials provide comparable or superior reflectivity while enabling more compact device designs and maintaining stability at high temperatures above 500°C.
Solution Approach 2:
The patent employs composite material structures, specifically transition metal dichalcogenides (TMDs) like WS2 and MoS2, which combine the beneficial properties of high reflectivity with thermal stability. These composite materials replace traditional single-element metals and provide both compactness and high-temperature reliability.
2Reliability
If Mo is used for high reflectivity, then reflectivity is improved, but industrial manufacturing becomes difficult due to high melting point
Solution Approach 1:
The patent transitions from elementally pure metals like Mo to compound materials such as MoS2 and WS2. These compounds can be manufactured using established semiconductor fabrication techniques including chemical vapor deposition (CVD) and atomic layer deposition (ALD), making them industrially processable despite the high melting points of their constituent elements.
3Volume of moving object
If compact design is implemented, then device size is reduced, but achieving sufficient reflectivity becomes difficult
Solution Approach 1:
The patent utilizes materials with inherently superior acoustic impedance mismatch properties, such as WS2 and MoS2, which provide higher reflectivity per unit thickness compared to traditional metals. This allows the same reflectivity to be achieved with thinner layers, enabling compact device designs without sacrificing reflectivity performance.
4Temperature
If high temperature operation is required, then temperature stability is improved, but material property changes affect electrical response
Solution Approach 1:
The patent employs transition metal dichalcogenide composite materials that maintain their crystal structure and physical properties at high temperatures. These materials exhibit minimal thermal expansion and maintain stable acoustic and electrical properties up to and beyond 500°C, ensuring reliable sensor operation in high-temperature environments where traditional metals would deteriorate.
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 increased reflectivity and temperature stability, enabling the use of SAW devices in high-temperature applications above 500°C with improved sensitivity and reduced device size, while maintaining compatibility with standard manufacturing processes.
Implementation Method 1
Bragg reflectors, formed by a large array of short-circuited metallic fingers, are provided on each side of the IDT to reflect the surface acoustic waves and create a cavity
Implementation Method 2
Surface acoustic waves are formed by inter-digitated transducers (IDT) provided on piezoelectric substrates
Implementation Method 3
Surface acoustic waves are formed by inter-digitated transducers (IDT) provided on piezoelectric substrates
Data Source
AI summary
A surface acoustic wave (SAW) device comprises an interdigitated transducer structure and at least one acoustic wave reflective structure provided on or in an acoustic wave propagating substrate. The interdigitated transducer structure comprises a first material and the at least one acoustic wave reflective structure comprises a second material different from the first material and/or the acoustic wave reflective structure and the interdigitated transducer structure have different geometrical parameters. A sensor comprises a SAW device as described herein, and a method is used for manufacturing a SAW device comprising at least one acoustic wave reflective structure.