Direct Substrate Bonding With Humidity-Controlled Annealing
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Solution Overview
Problem
Existing bonding processes by direct adhesion of substrates result in inhomogeneous adhesion energy, particularly at the edges, leading to substrate detachment and defects during thin film transfer using Smart Cut™ technology.
Innovation Solution
A method involving bonding substrates at a controlled relative humidity level and subsequent thermal annealing under an atmosphere with maintained or increased humidity, ensuring homogeneous adhesion energy by preventing water diffusion at the bonding interface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If direct adhesion bonding is performed without controlled humidity management during thermal annealing, then the bonding process is simple, but the adhesion energy becomes inhomogeneous leading to substrate detachment and defects
Solution Approach 1:
The invention changes the humidity parameter of the gaseous atmosphere during thermal annealing to prevent water diffusion from the bonding interface. By maintaining or increasing relative humidity (φ2 ≥ φ1) during the annealing process, the water concentration gradient is eliminated, preventing water migration from the interface to the edges and thus maintaining homogeneous adhesion energy throughout the bonded substrates.
Solution Approach 2:
The invention uses a controlled gaseous atmosphere with specific humidity characteristics to create an environment that prevents unwanted water diffusion. The atmosphere acts as a controlled medium that maintains equilibrium water concentration at the bonding interface, preventing the formation of low adhesion energy zones at the substrate edges.
2Reliability
If thermal annealing is performed in a dry atmosphere to remove moisture, then water is eliminated from the system, but water diffuses out of the bonding interface creating inhomogeneous adhesion energy
Solution Approach 1:
Instead of treating water as a harmful contaminant to be completely removed, the invention converts the presence of water into a beneficial factor by controlling its humidity in the atmosphere. The controlled humidity environment prevents water diffusion from the interface by maintaining equilibrium, thus the water that would otherwise cause detachment is transformed into a medium that ensures homogeneous adhesion energy distribution.
3Productivity
If conventional direct bonding is performed without humidity control, then the process is fast and simple, but substrate detachment occurs during fracturing due to inhomogeneous adhesion
Solution Approach 1:
The invention modifies the humidity parameter of the processing atmosphere during thermal annealing to achieve homogeneous adhesion energy. By controlling the relative humidity to be φ2 ≥ φ1, the process maintains water concentration equilibrium at the bonding interface, preventing edge effects and ensuring uniform adhesion throughout the substrate, thereby eliminating detachment during subsequent fracturing operations.
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
Significantly improves adhesion energy homogeneity, reducing substrate detachment and defects during thin film transfer.
Implementation Method 1
preventing the water present at the bonding interface, at the edge of the substrate, from diffusing out of the bonding interface
Implementation Method 2
applying a thermal annealing to the bonded first and second substrates, at a thermal annealing temperature between 100°C and 700°C
Implementation Method 3
The adhesion comes mainly from the van der Waals forces resulting from the electronic interaction between the atoms or molecules of two surfaces
Data Source
Figure 1~2
Figure 3a~3e
AI summary
This bonding process by direct adhesion of a first substrate (1) to a second substrate (2) comprises the following successive steps: a) preparing the first and second substrates (1, 2), each comprising a first surface (10, 20) and a second opposite surface (11, 21); b) bonding the first substrate (1) to the second substrate (2) by direct adhesion between the first surfaces (10, 20) of the first and second substrates (1, 2), step b) being carried out under a first gaseous atmosphere having a first relative humidity, denoted ϕ1; c) applying thermal annealing to the bonded first and second substrates (1, 2), at a thermal annealing temperature between 20°C and 700°C, step c) being carried out under a second gaseous atmosphere (3) having a second humidity, denoted ϕ2, satisfying ϕ2 ≥ ϕ1.