Substrate Bonding via Thermal Deformation and Surface Activation
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Solution Overview
Problem
Large-sized microchips face bonding challenges due to substrate warpage and undulation, leading to defective bonds, air bubbles, and stress concentration, which hinder the production of microchips with multiple measurement units and varied structures.
Innovation Solution
A method of bonding substrates where one substrate is deformed to conform to the shape of the other by heating above its deformable temperature but below the other's, ensuring close contact and high adhesion, using surface activation techniques like ultraviolet irradiation or plasma treatment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If adhesive bonding is used to bond two substrates, then bonding strength is improved, but the adhesive may seep into the minute flow path causing clogging, narrowing, or uneven diameter
Solution Approach 1:
The adhesive is completely removed from the bonding process. Instead of using adhesive bonding, the patent employs direct substrate-to-substrate bonding through surface activation (plasma treatment or UV irradiation) followed by thermal fusion, eliminating the risk of adhesive contamination in the flow path entirely
Solution Approach 2:
The patent introduces an intermediary bonding mechanism involving plasma-treated or UV-activated surfaces that create strong adhesion without requiring traditional adhesives. The activated surfaces form a bonding interface that achieves strong bonding while maintaining flow path integrity
2Strength
If thermal fusion bonding is used at high temperature, then bonding strength is improved, but the flow path may be crushed or deformed at the heating step
Solution Approach 1:
The patent changes the bonding parameters by using lower temperatures (below the glass transition temperature of the substrate) combined with surface activation. This alternative parameter combination achieves strong bonding without the high temperatures that would deform the flow path
Solution Approach 2:
The patent performs preliminary surface activation (plasma treatment or UV irradiation) before bonding to enhance adhesion. This preliminary action allows subsequent bonding to proceed at lower temperatures, preventing flow path deformation while maintaining bonding strength
3Reliability
If vacuum ultraviolet irradiation or plasma treatment is used to activate bonding surfaces, then bonding reliability is improved, but the process complexity increases
Solution Approach 1:
The patent employs atmospheric pressure plasma treatment that can be performed in ambient conditions without requiring vacuum systems. The plasma treatment self-activates the substrate surfaces in situ, eliminating the need for separate vacuum ultraviolet irradiation equipment and simplifying the overall process
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 method achieves reliable high-adhesion bonding of substrates with warpage or undulation, enabling the production of large-sized microchips with consistent flow paths and multiple measurement structures.
Implementation Method 1
irradiating vacuum ultraviolet rays to each of the bonding surfaces of two substrates, or converting a process gas into plasma under atmospheric pressure or in the vicinity thereof and bringing the plasma-converted process gas into contact with the surface of the substrate, thereby activating the bonding surface of each substrate
Implementation Method 2
a deforming step of deforming the bonding surface of the second substrate to conform to a shape of the bonding surface of the first substrate, and the deforming step is performed by heating a stacked body of the first substrate and the second substrate obtained in the stacking step at a temperature not lower than the deformable temperature of the second substrate
Data Source
AI summary
The present invention has as its object the provision of a method of bonding substrates, which can bond two substrates, at least one of which has warpage and undulation of a bonding surface, in a high adhesion state and a method of producing a microchip.In the method of bonding substrates according to the present invention, the first substrate is formed of a material having a deformable temperature at which the substrate deforms and which is higher than a deformable temperature of the second substrate, the method includes: a surface activation step of activating each of bonding surfaces of the first substrate and the second substrate; a stacking step of stacking the first substrate and the second substrate so that the respective bonding surfaces thereof are in contact with each other; and a deforming step of deforming the bonding surface of the second substrate to conform to a shape of the bonding surface of the first substrate, and the deforming step is performed by heating the stacked body of the first substrate and the second substrate obtained in the stacking step at a temperature not lower than the deformable temperature of the second substrate and lower than the deformable temperature of the first substrate.