SiO2 Substrate Joining Under Controlled Vacuum to Reduce Voids
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Solution Overview
Problem
Existing methods for manufacturing substrates with SiO2 thin films and piezoelectric thin films face issues with void formation due to excessive or deficient moisture at the joint interface, leading to inadequate joint strength.
Innovation Solution
A method involving plasma activation of SiO2 surfaces, followed by joining at a vacuum of 1 mbar to 400 mbar and subsequent heating to covalently bond hydroxy groups, effectively managing moisture to reduce voids and enhance joint strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If plasma activation is performed and bonding is performed with moisture present, then joint strength can be improved through covalent bond formation via OH groups, but voids are generated after heating due to excessive moisture
Solution Approach 1:
The patent applies parameter changes by precisely controlling the moisture content at the joint interface through vacuum degree control during the joining step. By adjusting the vacuum degree to a specific range (1 to 400 mbar), the moisture content is optimized to provide sufficient OH groups for covalent bond formation while preventing excessive moisture that would form voids during heating. This parameter optimization resolves the contradiction between joint strength and void formation.
2Manufacturing precision
If moisture at the joint interface is reduced to prevent void formation, then voids are reduced, but joint strength becomes deficient due to insufficient OH groups for covalent bonding
Solution Approach 1:
The patent resolves this contradiction by establishing an optimal vacuum degree range (1 to 400 mbar) that balances moisture content. This parameter setting ensures sufficient OH groups are present for strong covalent bonding while preventing excessive moisture accumulation that would create voids. The controlled vacuum environment allows precise moisture management to simultaneously achieve both goals.
3Manufacturing precision
If joining is performed at high vacuum to remove moisture, then void formation is reduced, but joint strength is compromised due to insufficient moisture for OH group generation
Solution Approach 1:
The patent addresses this contradiction by defining a specific vacuum degree range (1 to 400 mbar) that prevents the over-removal of moisture. This controlled vacuum level maintains sufficient moisture for OH group generation and covalent bonding while still removing enough moisture to prevent excessive void formation during heating. The parameter optimization balances both requirements.
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 effectively reduces void formation and enhances joint strength by controlling moisture levels during the bonding process, resulting in a robust joined body.
Implementation Method 1
an activating step of activating respective surfaces of a first substrate and a second substrate having the surfaces each including SiO2 as a main component by a plasma
Implementation Method 2
a heating step of heating the joined first SiO2 layer and second SiO2 layer joined with each other, and removing water generated at a joint surface thereof
Data Source
AI summary
A method for manufacturing a joined body, includes: an activating step of activating respective surfaces of a first substrate and a second substrate having the surfaces each including SiO2 as a main component by a plasma; a joining step of joining the activated surfaces of the first substrate and the second substrate at a degree of vacuum of 1 mbar or more and 400 mbar or less; and a heating step of heating the first substrate and the second substrate joined with each other. As a result of this, the manufacturing method and the joining method of a joined body capable of combining the reduction of generation of voids and the joint strength are provided.