Direct Bonding Interface Using Cationic Solution at Low Thermal Budget
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Solution Overview
Problem
Existing direct bonding methods face challenges such as the need for plasma treatment, which can be incompatible with certain substrates, increase costs, and affect surface quality, leading to potential electrical disruption and high thermal budgets.
Innovation Solution
A method involving direct bonding between substrates using a cationic aqueous solution comprising deionized water and cationic species from the first and/or second column of the periodic table, followed by a heat treatment at low temperatures (20° C. to 350° C.) to achieve high bonding energy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If plasma treatment is used to increase bonding energy, then bonding energy increases rapidly, but substrate compatibility decreases and surface quality is affected
Solution Approach 1:
The patent introduces a cationic aqueous solution as an intermediary substance between the bonding surfaces. This solution contains cations (such as Na+, K+, Ca2+, Mg2+) that mediate the bonding process by forming ionic bridges between negatively charged surface groups on opposing substrates, thereby achieving high bonding energy without direct plasma exposure to the substrates.
Solution Approach 2:
The patent replaces the plasma treatment mechanism (which involves complex physical and chemical processes including ion bombardment and surface modification) with a simpler chemical solution-based approach. The cationic solution works through ionic interactions and chemical bonding rather than high-energy plasma physics, making the process more compatible with sensitive substrates.
2Strength
If plasma treatment is used to increase bonding energy, then bonding energy increases, but treatment time and cost increase
Solution Approach 1:
The patent employs a simple aqueous cationic solution that can be easily prepared, applied, and disposed of or reused. Unlike plasma treatment which requires complex equipment setup, maintenance, and operation, the chemical solution approach uses inexpensive reagents and simple application methods, significantly reducing both time and cost overhead.
3Strength
If plasma treatment is used to increase bonding energy, then bonding energy increases, but thermal budget increases
Solution Approach 1:
The patent replaces thermal plasma processes with a chemical solution process that operates at or near ambient temperature. The cationic aqueous solution achieves bonding through ionic interactions and chemical affinity rather than thermal energy, thereby eliminating the need for high thermal budgets while still achieving high bonding energy.
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 high bonding energy without affecting adhesion energy, is compatible with various substrates and electronic components, and reduces thermal budgets, while maintaining mechanical strength and applicability to diverse materials.
Implementation Method 1
depositing at least the direct bonding interface in a cationic aqueous solution comprising deionized water and cationic species from at least one element of the first and/or second column of the periodic table of elements
Implementation Method 2
applying a heat treatment at a temperature comprised between 20° C. and 350° C. so as to obtain the multilayer structure
Implementation Method 3
direct bonding is spontaneous bonding between two surfaces without adding material to the interface between the bonded surfaces... so that the Van der Waals forces can be implemented
Data Source
AI summary
A method for manufacturing a multilayer structure by direct bonding between a first substrate and a second substrate, the method including the steps of: providing a first substrate and a second substrate respectively including a first bonding surface and a second bonding surface, contacting the first bonding surface and the second bonding surface so as to create a direct bonding interface between the first substrate and the second substrate, placing at least the direct bonding interface in a cationic aqueous solution including deionized water and cationic species originating from at least one element of the first and/or of the second column of the periodic table of elements, and applying a heat treatment at a temperature comprised between 20° C. and 350° C. so as to obtain the multilayer structure.