Acoustic Wave Membrane Structure for Flat Piezoelectric Films
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing acoustic wave devices face issues with undulation on the support layer surface due to sacrificial layer removal, leading to variations in the thickness of the piezoelectric thin film, which can cause unnecessary wave generation and deteriorate frequency characteristics.
Innovation Solution
The introduction of a spacer layer made of a different material, located in areas other than the cavity portion, helps in reducing undulation and thickness variations of the piezoelectric layer by providing a stable surface for bonding and etching processes, thereby minimizing the generation of unnecessary bulk waves and maintaining frequency stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If the support layer is flattened after bonding the support substrate, then the surface should be flat, but undulation occurs due to the influence of the support substrate's high rigidity
Solution Approach 1:
The patent applies preliminary action by performing flattening treatment on the support layer before bonding it to the piezoelectric substrate. This pre-flattening step ensures that the support layer surface is sufficiently flat before the bonding process, preventing undulation from occurring during or after bonding due to the support substrate's rigidity. The flattening treatment is conducted in advance to establish the proper surface geometry before subsequent processing steps.
2Productivity
If the piezoelectric thin film thickness is reduced to form a piezoelectric substrate, then device integration is improved, but thickness variation occurs leading to unnecessary wave generation
Solution Approach 1:
The patent introduces an intermediary layer between the support layer and the piezoelectric substrate. This intermediary layer acts as a mediator that compensates for thickness variations in the piezoelectric thin film. By providing this intermediate buffering layer, the system can accommodate variations in piezoelectric film thickness without directly transmitting these variations to the final device structure, thereby preventing unnecessary wave generation while maintaining integration efficiency.
3Adaptability or versatility
If a sacrificial layer is removed to form a hollow space, then device functionality is improved, but surface undulation and thickness variation are caused
Solution Approach 1:
The patent applies preliminary anti-action by providing a reinforcing structure in the support layer at the location where the hollow space will be formed. This reinforcing structure is prepared in advance to counteract the surface undulation that would otherwise occur when the sacrificial layer is removed. By pre-establishing this counteracting structure, the patent prevents the harmful surface deformation before the hollow space formation process completes, thereby maintaining surface flatness while preserving device functionality.
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 effectively reduces thickness variations in the piezoelectric layer, preventing the generation of unnecessary bulk waves and improving the frequency characteristics of the acoustic wave device.
Implementation Method 1
a piezoelectric layer (14) on the intermediate layer (15)
Data Source
AI summary
An acoustic wave device includes a support including support substrate and an intermediate layer on the support substrate, a piezoelectric layer on the intermediate layer, and an IDT electrode on the piezoelectric layer. A cavity portion is provided in the support. The piezoelectric layer includes a membrane portion overlapping the cavity portion in a plan view. At least a portion of the IDT electrode is in the membrane portion. A spacer layer is in the support and made of a material different from materials of the piezoelectric layer and the intermediate layer. The spacer layer is located in a portion other than the cavity portion.