Direct Bonding Interface Using Cationic Solution at Low Temperature
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Solution Overview
Problem
Existing direct bonding methods face challenges in achieving high bonding energy at low temperatures, particularly below 400°C, while being compatible with various substrates and electronic components, and often require plasma treatment that can be costly and disruptive to device operation.
Innovation Solution
A method involving direct bonding between substrates with a cationic aqueous solution containing deionized water and cationic species from the first and/or second column of the periodic table, followed by a heat treatment between 20°C and 350°C, to enhance bonding energy without affecting mechanical strength or device integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If plasma treatment is used to increase bonding energy, then bonding energy increases quickly, but process cost and complexity increase
Solution Approach 1:
The patent replaces expensive and complex plasma treatment with a simple aqueous solution treatment using common salts (NaCl, KCl, CaCl2, etc.). The solution is inexpensive, easy to prepare, and can be disposed of after use, eliminating the need for complex plasma generation equipment and reducing process costs while achieving the same bonding energy enhancement.
Solution Approach 2:
The patent substitutes the plasma treatment mechanism (electromagnetic field-based) with a chemical solution-based mechanism. Instead of using plasma to modify surface properties, the patent uses cationic species in aqueous solution to achieve surface modification, thereby simplifying the equipment requirements and reducing process complexity.
2Strength
If plasma treatment is applied to increase bonding energy, then bonding energy reaches 5 J/m2, but substrate compatibility decreases
Solution Approach 1:
The patent uses inexpensive aqueous salt solutions that can be safely applied to various substrates without causing damage. These solutions are compatible with substrates containing electronic components, unlike plasma treatment which can generate uncontrolled oxide layers and interfacial charges that disrupt device operation.
Solution Approach 2:
The patent creates a chemically gentle environment using aqueous salt solutions that do not aggressively react with substrates. This inert-like environment allows safe treatment of sensitive substrates and devices, maintaining substrate compatibility while still achieving high bonding energy through cationic species adsorption.
3Strength
If high temperature heat treatment is used to increase bonding energy, then bonding energy increases, but thermal damage to devices occurs
Solution Approach 1:
The patent changes the bonding energy enhancement mechanism from thermal activation to chemical activation. By using cationic species adsorption at low temperatures (20-100°C) followed by mild heat treatment (up to 350°C), the patent achieves high bonding energy without subjecting devices to high temperatures that would cause thermal damage.
Solution Approach 2:
The patent introduces cationic species (Na+, K+, Ca2+, etc.) as intermediaries to facilitate bonding at low temperatures. These cationic species adsorb on substrate surfaces and create strong electrostatic interactions, enabling high bonding energy to be achieved without relying on high temperature thermal activation, thereby avoiding thermal damage to electronic components.
4Strength
If conventional cleaning methods are used to prepare surfaces, then adhesion energy reaches 140 mJ/m2, but process time and cost increase
Solution Approach 1:
The patent combines the cleaning function and bonding enhancement function into a single step. The aqueous salt solution both cleans the substrate surfaces and deposits cationic species that enhance bonding energy, eliminating the need for separate cleaning and bonding preparation steps, thereby reducing process time and complexity.
Solution Approach 2:
The aqueous salt solution serves multiple functions: it acts as a cleaning agent, a source of cationic species for surface modification, and a bonding enhancement medium. This multi-functional approach replaces multiple separate processes (cleaning, plasma treatment, bonding preparation) with a single versatile treatment, reducing overall process time and cost.
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 at low temperatures, compatible with diverse substrates and electronic components, maintaining mechanical strength and avoiding thermal damage to devices, with the process being cost-effective and applicable to numerous materials.
Implementation Method 1
arranging at least the direct bonding interface in a cationic aqueous solution comprising deionized water and cationic species derived from at least one element from the first and/or second column of the periodic table of elements
Implementation Method 2
cationic species derived from at least one element from the first and/or second column of the periodic table of elements
Implementation Method 3
the energy that allows the two surfaces to be deformed to bring them into contact at the atomic scale so that the Van der Waals forces can be implemented
Implementation Method 4
applying a heat treatment at a temperature between 20°C and 350°C so as to obtain the multilayer structure
Data Source
Figure 1~3
AI summary
A method for manufacturing a multilayer structure (100) by direct bonding between a first substrate (1) and a second substrate (2), the method comprising the steps of: a) supplying a first substrate (1) and a second substrate (2) comprising respectively a first bonding surface (3) and a second bonding surface (4), b) bringing the first bonding surface (3) and the second bonding surface (4) into contact so as to create a direct bonding interface (6) between the first substrate (1) and the second substrate (2), c) disposing of at least the direct bonding interface (6) in a cationic aqueous solution (8) comprising deionized water and cationic species from at least one element of the first and/or second column of the periodic table of elements, and d) applying a heat treatment at a temperature between 20°C and 350°C so as to obtain the multilayer structure (100).