Strong Base Direct Bonding for Plasma-Free Hydrophilic Substrates
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Solution Overview
Problem
Existing direct bonding methods require plasma treatment, which can be incompatible with certain substrates, lengthen processing times, and increase costs, and may modify the surface, affecting the quality and electrical operation of future devices, while also requiring high annealing temperatures to achieve sufficient bonding energy.
Innovation Solution
A direct bonding method involving the application of a basic solution with strong base molecules and deionized water on hydrophilic surfaces, followed by drying to achieve a specific concentration of cations, allowing spontaneous bonding without plasma treatment and reducing the need for high annealing temperatures, thereby enhancing bonding energy without altering adhesion 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 modification occurs that may affect future devices
Solution Approach 1:
The patent introduces a basic solution (mediator) consisting of water and a basic substance as an intermediary between the substrate surfaces. This basic solution modifies the surface chemistry to enhance bonding energy without requiring plasma treatment, thereby maintaining substrate compatibility and avoiding unwanted surface modifications that would affect future device operation.
2Strength
If plasma treatment is used to increase bonding energy, then bonding energy increases rapidly, but processing time and costs increase
Solution Approach 1:
The patent replaces expensive and time-consuming plasma treatment with a simple, inexpensive basic solution that can be applied and removed quickly. The basic solution serves its purpose of enhancing bonding energy and then can be discarded, providing a cost-effective and time-efficient alternative to plasma processing.
3Strength
If high annealing temperatures are used to achieve sufficient bonding energy, then bonding energy increases, but substrate damage risk increases and temperature-sensitive substrates cannot be processed
Solution Approach 1:
The patent changes the chemical parameters of the bonding interface by introducing a basic solution, which modifies the surface chemistry and enables sufficient bonding energy to be achieved at lower annealing temperatures. This parameter change in the chemical environment allows temperature-sensitive substrates to be processed without damage while still achieving the required bonding strength.
4Strength
If conventional cleaning methods are used to remove contaminations, then adhesion energy increases, but additional processing steps and time are required
Solution Approach 1:
The patent merges the cleaning function and bonding enhancement function into a single step by using the basic solution. The basic solution both removes contaminations from the substrate surfaces and simultaneously prepares the surfaces for enhanced bonding, eliminating the need for separate cleaning and bonding preparation steps, thereby improving processing efficiency.
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 achieves immediate and resistant direct bonding with increased bonding energy, compatible with conventional microelectronics handling, and does not require specific handling or pressure, while maintaining low cycle times and costs, and is applicable to temperature-sensitive substrates.
Implementation Method 1
The adhesion 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 2
depositing on the first and/or on the second hydrophilic bonding surface a basic solution consisting of strong base molecules and deionized water
Data Source
AI summary
A direct bonding method between two substrates includes the steps of: providing a first substrate and a second substrate respectively including a first hydrophilic bonding surface and a second hydrophilic bonding surface; depositing on the first and/or on the second hydrophilic bonding surface a basic solution consisting of strong base molecules and deionized water; drying the first and/or the second hydrophilic bonding surface until a concentration with between approximately 109 atom/cm2 and 1015 atom/cm2 of cations resulting from the strong base molecules on the first and/or on the second hydrophilic bonding surface; contacting the first and the second hydrophilic bonding surface so as to obtain a spontaneous direct bonding and an assembly of the first substrate with the second substrate including a direct bonding interface.