Composite Substrate Bonding with Controlled Oxide Surface Waviness
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Solution Overview
Problem
Existing composite substrates for surface acoustic wave devices lack durability during processing, leading to issues like peeling at the joining interface during grinding or polishing.
Innovation Solution
A method involving the formation of a silicon oxide layer on a piezoelectric substrate, followed by flattening treatment to achieve a surface waviness between 2 nm and 70 nm, and subsequent activation treatment by plasma irradiation before joining a support substrate, enhances the durability of the composite substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a composite substrate is formed by joining a piezoelectric substrate and a support substrate, then the device characteristics are improved, but the durability during processing deteriorates due to peeling at the joining interface
Solution Approach 1:
An intermediate layer is introduced between the piezoelectric substrate and the support substrate to act as a mediator that improves adhesion and prevents peeling during processing. This intermediate layer serves as a bonding interface that strengthens the joint while allowing the composite substrate to maintain its functional characteristics.
Solution Approach 2:
The surface of the piezoelectric substrate undergoes preliminary treatment (such as roughening or chemical treatment) before joining to enhance surface energy and adhesion. This preliminary action prepares the surface to better bond with the intermediate layer, preventing subsequent peeling during grinding or polishing operations.
2Device complexity
If the piezoelectric substrate is joined directly to the support substrate, then the structure is simple, but the durability during processing deteriorates
Solution Approach 1:
An intermediate layer is introduced between the piezoelectric substrate and the support substrate to act as a mediator that improves adhesion and prevents peeling during processing. This intermediate layer serves as a bonding interface that strengthens the joint while allowing the composite substrate to maintain its functional characteristics.
3Manufacturing precision
If the composite substrate undergoes grinding or polishing treatment, then the surface quality is improved, but peeling occurs at the joining interface
Solution Approach 1:
The intermediate layer is designed to have mechanical properties that cushion and distribute the stresses generated during grinding or polishing. This layer absorbs the mechanical shocks and prevents stress concentration at the joining interface, thereby preventing peeling while allowing surface quality improvement.
Solution Approach 2:
The intermediate layer acts as a protective mediator during mechanical processing, shielding the joining interface from the direct impact of grinding or polishing forces while still allowing the surface to be refined to high quality standards.
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 method results in a composite substrate with improved durability, reducing the occurrence of peeling during processing and ensuring strong joining between the piezoelectric and support substrates, thus enhancing the quality and reliability of the composite substrate.
Implementation Method 1
the activation treatment is performed by plasma irradiation
Data Source
AI summary
A method of producing a composite substrate includes: forming a first layer on a lower surface side of a piezoelectric substrate having an upper surface and a lower surface facing each other and having an electrode formed on the lower surface; performing flattening treatment to set a waviness of a surface of the first layer to more than 2 nm and 70 nm or less; and joining a support substrate to a first layer side of the piezoelectric substrate having the first layer formed thereon.