Acoustic Wave Layer Stack Using C56 Contrast to Suppress Spurious Modes
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing acoustic wave devices suffer from high-order mode spurious emissions, which deteriorate the characteristics of the main mode, leading to issues in frequency stability and filter performance.
Innovation Solution
The acoustic wave device incorporates a material layer with specific Euler angles and a piezoelectric body, where the elastic constant C56 of the material layer is greater than that of the piezoelectric body, and a thin piezoelectric body with a thickness equal to or smaller than 10λ, to effectively reduce or prevent high-order mode responses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a piezoelectric body is laminated on a silicon substrate with an SiO2 film, then the main mode energy is concentrated in the piezoelectric body, but high-order modes are also confined in the piezoelectric body causing spurious emissions
Solution Approach 1:
The patent segments the acoustic wave propagation path by introducing a specific material layer between the piezoelectric body and silicon substrate. This material layer has different elastic constants (specifically C56) than the piezoelectric body, creating distinct regions that guide different modes differently - main mode energy remains concentrated in the piezoelectric body while high-order modes are diverted into the material layer, preventing spurious emissions.
Solution Approach 2:
The patent applies local quality by selecting a material layer with specific local properties (elastic constant C56 relationship) at a specific location (between piezoelectric body and substrate). The material layer's C56 is designed to be greater than that of the piezoelectric body, creating a localized elastic property difference that selectively affects high-order modes without compromising main mode concentration.
2Object-generated harmful factors
If the piezoelectric body thickness is reduced to 10λ or less, then high-order mode responses are reduced, but manufacturing precision requirements increase
Solution Approach 1:
The material layer acts as an intermediary that relaxes the manufacturing precision requirement. By introducing this intermediate layer with specific elastic properties, the system can achieve high-order mode suppression through the combined thickness of piezoelectric body and material layer, rather than requiring extremely precise control of piezoelectric body thickness alone. The material layer provides an additional degree of freedom for mode control.
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 configuration significantly reduces high-order mode responses while maintaining the characteristics of the main mode, enhancing frequency stability and filter performance by confining the main mode and minimizing additional high-order mode generation.
Implementation Method 1
a piezoelectric body which includes first and second principal surfaces opposing each other, is laminated directly or indirectly on the material layer
Implementation Method 2
whose elastic constant at the Euler angles (φ2, θ2, ψ2) is represented by the Expression (1), and an interdigital transducer (IDT) electrode which is disposed on one of the first principal surface and the second principal surface of the piezoelectric body
Data Source
AI summary
An acoustic wave device includes a material layer with Euler angles and an elastic constant at the Euler angles represented by Expression 1, a piezoelectric body including opposing first and second principal surfaces, is laminated directly or indirectly on the material layer and has Euler angles, and whose elastic constant at the Euler angles is represented by the Expression 1 below, and an IDT electrode on at least one of first and second principal surfaces of the piezoelectric body, and in which a wave length determined by an electrode finger pitch is λ. A product of C56 and C56 has a positive value, and an absolute value of C56 of the material layer is greater than an absolute value of C56 of the piezoelectric body(C11C12C13C14C15C16C21C22C23C24C25C26C31C32C33C34C35C36C41C42C43C44C45C46C51C52C53C54C55C56C61C62C63C64C65C66).Expression1