Inclined-Crystal Acoustic Wave Structure for Lower Propagation Loss
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Solution Overview
Problem
Existing acoustic wave device manufacturing processes are complex and result in high propagation loss due to the difficulty in aligning the crystal axis of lithium niobate films perpendicular to the film, necessitating bulk monocrystal cutting.
Innovation Solution
The manufacturing process involves forming a piezoelectric layer with a second crystal axis aligned at an equal inclination angle to a first crystal axis of the support substrate, using a thin-film formation method to align rotational symmetries, thereby eliminating the need for bulk monocrystal cutting and reducing propagation loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a lithium niobate film is formed on a substrate using conventional film-formation technology, then the manufacturing process is simplified, but the crystal axis is oriented perpendicular to the film instead of being inclined, resulting in higher propagation loss
Solution Approach 1:
The patent changes the crystal orientation parameter by forming the piezoelectric layer with an inclined crystal axis (e.g., 36.2° inclination) rather than perpendicular orientation. This is achieved through specific film formation conditions that control crystal growth direction, allowing the c-axis to be inclined relative to the film normal while maintaining film-forming technology benefits
Solution Approach 2:
The patent uses a composite structure consisting of a support substrate, intermediate layers, and a piezoelectric layer with specific crystal orientation. The piezoelectric layer is formed as a thin film with controlled crystal axis inclination, combining the advantages of film formation simplicity with the performance benefits of inclined crystal orientation
2Loss of energy
If a bulk monocrystal of lithium niobate is cut into a plate shape to achieve inclined crystal axis orientation, then propagation loss is reduced, but the manufacturing process becomes complex and time-consuming
Solution Approach 1:
The patent extracts the essential requirement of inclined crystal axis orientation from the bulk monocrystal cutting process. Instead of cutting bulk material, the invention forms a thin piezoelectric layer with controlled crystal orientation using film formation technology, separating the crystal orientation control from the bulk material processing
Solution Approach 2:
The patent replaces the mechanical cutting process with a film formation process. Instead of mechanically cutting bulk monocrystals to achieve inclined orientation, the invention uses controlled deposition or growth methods to form thin films with the desired crystal axis inclination, substituting mechanical processing with a more precise and simpler film formation technique
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 simplifies the manufacturing process and reduces propagation loss by ensuring equal rotational symmetry between the piezoelectric and support substrates, enhancing piezoelectricity and improving frequency-temperature characteristics.
Implementation Method 1
piezoelectricity generated in a direction perpendicular to the film is higher when the c axis is oriented to a direction inclined from the direction perpendicular to the film
Data Source
AI summary
An acoustic wave device includes a support substrate including a first crystal axis, first and second intermediate layers, a piezoelectric layer including a second crystal axis, and a functional electrode on the piezoelectric layer. The support substrate, the first and second intermediate layers, and the piezoelectric layer are arranged in this order. The first crystal axis is inclined at a first inclination angle with respect to a direction normal to the support substrate. The second crystal axis is inclined at a second inclination angle with respect to a direction normal to the piezoelectric layer. The first and second inclination angles are equal to each other. Rotational symmetry of the piezoelectric layer with respect to the second crystal axis is equal to rotational symmetry of the support substrate with respect to the first crystal axis.