Acoustic Wave Support Structure for Thin Substrate Strength
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Solution Overview
Problem
Thinning the support for a piezoelectric layer in acoustic wave devices often degrades their mechanical strength, which is a challenge in maintaining effective resonance characteristics and Q factor.
Innovation Solution
The acoustic wave device design includes a support structure with a first and second substrate, where the first substrate is made thinner while being supported on both sides by the second and third substrates, with hollows and sealing metal layers to prevent mechanical strength degradation, allowing for effective excitation of first-order thickness shear mode bulk waves without the need for reflectors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the support substrate is made thinner to reduce device size, then the device dimensions are reduced, but the mechanical strength of the support substrate is degraded
Solution Approach 1:
The support substrate is constructed as a composite structure combining a thin substrate layer with integrated reinforcing patterns (such as grid patterns, honeycomb structures, or triangular patterns) made of the same or different material. This composite design allows the overall structure to maintain high mechanical strength while keeping the substrate itself thin, thus reducing device size without sacrificing support strength.
Solution Approach 2:
The support substrate is divided into multiple segments or regions through the reinforcing patterns, creating a modular structure. This segmentation allows the thin substrate to be strengthened by the distributed reinforcing elements, which bear the mechanical loads while the thin substrate maintains its size-reduction benefit.
2Reliability
If the support substrate is made thinner to improve resonance characteristics, then the Q factor is improved, but the mechanical strength is degraded
Solution Approach 1:
The composite structure with reinforcing patterns provides the necessary mechanical strength to maintain high Q factor resonance characteristics. The thin substrate enables better resonance performance while the reinforcing patterns ensure the structure can sustain the mechanical stresses during vibration, preventing energy loss and maintaining reliability.
Solution Approach 2:
The reinforcing patterns are strategically placed in specific locations where mechanical strength is most needed, such as around the piezoelectric layer and in high-stress regions. This local reinforcement allows the majority of the substrate to remain thin for optimal resonance characteristics, while only adding material where mechanically necessary.
3Device complexity
If the support substrate is made thinner to reduce device complexity, then the structure is simplified, but the mechanical strength is degraded
Solution Approach 1:
The composite structure with integrated reinforcing patterns provides an elegant solution that does not significantly increase device complexity. The reinforcing patterns can be formed using standard semiconductor manufacturing processes (such as photolithography and etching), making the complex-looking structure actually quite straightforward to manufacture. This maintains simplicity in the manufacturing process while achieving the dual goals of thin substrate and high strength.
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 design enhances the mechanical strength of the support while maintaining good resonance characteristics and a high Q factor, even when the device is reduced in size, by preventing propagation loss and allowing for effective excitation of first-order thickness shear mode bulk waves.
Implementation Method 1
a piezoelectric layer adjacent to the first principal surface of the first substrate
Data Source
AI summary
An acoustic wave device includes a first substrate, a piezoelectric layer adjacent to a first principal surface of the first substrate, a functional electrode on the piezoelectric layer, a second substrate, and a third substrate. The second substrate is adjacent to the first principal surface of the first substrate and faces the first substrate, with a second hollow interposed therebetween. The third substrate is adjacent to a second principal surface of the first substrate and faces the first substrate, with a first hollow interposed therebetween. The acoustic wave device includes a first support portion between the first principal surface of the first substrate and the second substrate, and a second support portion between the first substrate and the third substrate.