Acoustic Wave Filter Stack for Spurious Suppression and Adhesion
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Solution Overview
Problem
The intermediate layer with pores in acoustic wave devices tends to peel off from the support substrate due to reduced adhesion, leading to performance issues and spurious emissions.
Innovation Solution
A multi-layer structure is introduced, with a first intermediate layer having pores, a second intermediate layer with a lower Q factor, and a third intermediate layer with higher porosity, all between the support substrate and the piezoelectric layer, to enhance adhesion and reduce spurious responses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If an intermediate layer with pores is provided between the support substrate and the piezoelectric layer to reduce spurious responses, then the spurious responses are attenuated, but the intermediate layer peels off from the support substrate due to reduced adhesion
Solution Approach 1:
The intermediate layer is divided into three distinct layers (first, second, and third intermediate layers) with different porosity characteristics. The first intermediate layer has moderate porosity for spurious response attenuation, the second intermediate layer has high porosity for enhanced adhesion to the piezoelectric layer, and the third intermediate layer has low porosity for enhanced adhesion to the support substrate. This segmentation allows each layer to optimize its function without compromising adhesion.
Solution Approach 2:
Different regions of the intermediate layer structure are assigned different porosity qualities tailored to their specific functions. The first intermediate layer maintains moderate porosity for spurious response attenuation, while the second and third intermediate layers have adjusted porosity (higher and lower respectively) to optimize adhesion at their respective interfaces. This local quality adjustment ensures that adhesion requirements are met at critical interfaces while maintaining the overall spurious response attenuation function.
2Reliability
If the porosity of the intermediate layer is increased to improve adhesion, then the adhesion is enhanced, but the spurious response attenuation capability is reduced
Solution Approach 1:
The intermediate layer is segmented into three layers with different porosity levels. The first intermediate layer maintains moderate porosity for spurious response attenuation, while the second and third intermediate layers have adjusted porosity specifically for adhesion enhancement at their interfaces. This segmentation allows porosity to be optimized for adhesion without compromising the spurious response attenuation function of the first intermediate layer.
Solution Approach 2:
Porosity is locally adjusted in different intermediate layers to meet specific functional requirements. The second intermediate layer has higher porosity to improve adhesion to the piezoelectric layer, while the third intermediate layer has lower porosity to improve adhesion to the support substrate. The first intermediate layer maintains moderate porosity for spurious response attenuation. This local quality differentiation resolves the contradiction by applying different porosity characteristics where needed.
3Object-generated harmful factors
If a single intermediate layer with moderate porosity is used for spurious response attenuation, then the spurious responses are reduced, but the adhesion to both support substrate and piezoelectric layer is insufficient
Solution Approach 1:
The single intermediate layer is segmented into three separate intermediate layers, each with optimized porosity for its specific function. The first intermediate layer handles spurious response attenuation, while the second and third intermediate layers specifically address adhesion at the piezoelectric layer interface and support substrate interface respectively. This segmentation allows simultaneous optimization of both adhesion interfaces and spurious response attenuation.
Solution Approach 2:
Different porosity qualities are assigned to different intermediate layers to meet local requirements. The first intermediate layer has moderate porosity for spurious response attenuation, the second intermediate layer has higher porosity for adhesion to the piezoelectric layer, and the third intermediate layer has lower porosity for adhesion to the support substrate. This local quality optimization ensures both interfaces have sufficient adhesion while maintaining spurious response attenuation capability.
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 improves the adhesion between the intermediate layers and the support substrate, preventing peeling and effectively attenuating spurious responses, thereby enhancing the overall performance of the acoustic wave device.
Implementation Method 1
a second intermediate layer provided between the support substrate and the first intermediate layer, the second intermediate layer having a porosity higher than a porosity of the first intermediate layer
Implementation Method 2
the second intermediate layer having a porosity higher than a porosity of the first intermediate layer
Implementation Method 3
a third intermediate layer provided between the support substrate and the second intermediate layer, the third intermediate layer having a porosity lower than the porosity of the second intermediate layer
Implementation Method 4
a piezoelectric layer provided on the support substrate
Data Source
AI summary
An acoustic wave device includes a support substrate, a piezoelectric layer provided on the support substrate, at least one pair of comb-shaped electrodes provided on the piezoelectric layer, the at least one pair of comb-shaped electrodes including a plurality of electrode fingers, a first intermediate layer provided between the support substrate and the piezoelectric layer, a second intermediate layer provided between the support substrate and the first intermediate layer, the second intermediate layer having a porosity higher than a porosity of the first intermediate layer, and a third intermediate layer provided between the support substrate and the second intermediate layer, the third intermediate layer having a porosity lower than the porosity of the second intermediate layer.