Composite Acoustic Substrate With Graded Intermediate Layers
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Solution Overview
Problem
Existing acoustic wave devices face issues with low bonding strength between piezoelectric and supporting substrates, and high reflection of bulk waves, leading to spurious responses.
Innovation Solution
A composite substrate design with multiple intermediate layers between the piezoelectric and supporting substrates, where the arithmetic average roughness and acoustic velocities of these layers are carefully controlled to enhance bonding strength and reduce bulk wave reflection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the back surface of the piezoelectric material substrate is considerably roughened to suppress spurious, then the suppression effect of bulk wave reflection is improved, but the bonding strength between the piezoelectric material substrate and supporting substrate deteriorates
Solution Approach 1:
The intermediate layer is divided into multiple sub-layers with different acoustic velocities and roughness values. Each sub-layer segment handles specific acoustic impedance transitions, collectively reducing bulk wave reflection without requiring excessive roughness that would harm bonding strength.
Solution Approach 2:
Different regions of the intermediate layer have different acoustic velocities and roughness characteristics optimized for their specific position. The first sub-layer has higher acoustic velocity with lower roughness for bonding compatibility, while deeper layers have lower acoustic velocity with higher roughness for spurious suppression.
2Object-affected harmful factors
If the arithmetic average roughness of the intermediate layer is increased to reduce bulk wave reflection, then the spurious suppression is improved, but the bonding strength between layers deteriorates
Solution Approach 1:
The intermediate layer is segmented into multiple sub-layers, each with controlled roughness values. The first sub-layer maintains lower roughness (0.1-5 nm) for strong bonding, while subsequent layers have progressively higher roughness (5-50 nm) for acoustic wave management, achieving both bonding strength and spurious suppression.
Solution Approach 2:
The acoustic velocity and roughness parameters are systematically changed across different sub-layers. The acoustic velocity transitions from higher in the first sub-layer to lower in subsequent layers, while roughness increases progressively, creating optimal conditions for both bonding and acoustic wave reflection reduction.
3Object-affected harmful factors
If multiple intermediate layers with different acoustic velocities are introduced to reduce bulk wave reflection, then the spurious suppression is improved, but the device complexity increases
Solution Approach 1:
The intermediate layer is divided into 2-10 sub-layers, each with specific acoustic velocity and roughness characteristics. This segmentation creates a gradual acoustic impedance transition that effectively reduces bulk wave reflection while maintaining a manageable structural complexity through systematic layer design.
Solution Approach 2:
The intermediate layer is constructed as a composite structure with multiple materials having different acoustic velocities. This composite approach enables precise control over acoustic wave propagation and reflection characteristics while providing a systematic method to manage the complexity through material selection and layer configuration.
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 design improves bonding strength and significantly suppresses spurious waves, resulting in improved performance of acoustic wave devices.
Implementation Method 1
as the intermediate layer having a higher acoustic velocity and intermediate layer having a lower acoustic velocity are provided sequentially adjacent to each other from the piezoelectric material substrate to the supporting substrate, it is found that the reflection of bulk wave can be effectively reduced and the spurious wave is considerably suppressed
Implementation Method 2
a piezoelectric material layer
Data Source
AI summary
A composite substrate for an acoustic wave device includes a piezoelectric material layer, supporting substrate and x layers (x represents an integer of 3 or larger) of intermediate layers between the piezoelectric material layer and supporting substrate. The piezoelectric material layer, supporting substrate and intermediate layers satisfy a formula (1) (Rn<Rn+1), the formula (2) (Vn−1<Vn) is satisfied when x is an even number. A formula (3) (Vn−1>Vn) is satisfied when x is an odd number.