Siloxane Bond Conversion for Direct Material Layer Bonding
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Solution Overview
Problem
Direct bonding between material layers, such as silicon oxide layers, often results in insufficient bonding energy due to low surface energy, which is inadequate for certain applications, despite prior planarization and heat treatments, with typical bonding energies being less than 2 J/m2 after heat treatment at 200°C for 2 hours.
Innovation Solution
A method involving a forced diffusion step of chemical species with free electrons and labile protons into the first material layer to convert siloxane bonds into silanol bonds, increasing surface energy by at least 10 nm depth, using a heated liquid or humid atmosphere, to enhance bonding energy between the layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If direct bonding is performed between planarized oxide layers, then surface smoothness is improved, but bonding energy remains insufficient (less than 2 J/m2)
Solution Approach 1:
The patent applies preliminary chemical treatment to the oxide layer surfaces before bonding to increase surface energy. Specifically, the surfaces are treated with plasma or chemical solutions to generate hydroxyl groups, which significantly increase surface energy and enable strong bonding. This preliminary action addresses the insufficiency of bonding energy that occurs when only mechanical planarization is performed.
2Strength
If heat treatment is applied to increase bonding energy, then bonding strength is improved, but treatment time is excessive (2 hours at 200°C)
Solution Approach 1:
The patent performs preliminary surface activation through plasma treatment or chemical solution treatment before bonding. This preliminary action increases surface energy by generating hydroxyl groups on the oxide surfaces, which enables strong bonding to occur with minimal or no subsequent heat treatment, thereby dramatically reducing the excessive heat treatment time required by conventional methods.
Solution Approach 2:
The patent changes the chemical state of the oxide surface by introducing hydroxyl groups through plasma or chemical treatment. This parameter change in surface chemistry (from hydrophobic to hydrophilic surfaces) fundamentally alters the bonding characteristics, enabling strong bonding without requiring prolonged thermal treatment.
3Temperature
If PECVD oxide layers are used for direct bonding, then deposition temperature is reduced (380°C), but bonding energy becomes insufficient
Solution Approach 1:
The patent applies preliminary plasma treatment or chemical solution treatment to PECVD oxide layers before bonding. This treatment generates hydroxyl groups on the PECVD oxide surfaces, significantly increasing their surface energy. As a result, PECVD oxide layers can be strongly bonded at low temperatures without requiring high-temperature processing, thus maintaining the advantage of low deposition temperature while achieving sufficient 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 effectively increases the surface energy of the material layers to greater than 1 J/m2, achieving bonding energies of 2.5 J/m2 or more after heat treatment, suitable for industrial applications, by converting siloxane bonds into silanol bonds, thereby improving the interlocking strength between the layers.
Implementation Method 1
comprising at least one forced diffusion step, at least in the first material layer, of chemical species comprising at least one pair of free electrons and at least one labile proton
Implementation Method 2
converting at least one portion of the siloxane bonds into silanol bonds in at least one portion of the first material layer
Implementation Method 3
using a heated liquid or humid atmosphere
Implementation Method 4
Heat treatments may be carried out during or after bonding to increase the bonding energy between the joined surfaces
Implementation Method 5
electronic interactive forces of attraction between the atoms or molecules of both surfaces to be bonded are created, for example Van der Waals forces
Data Source
AI summary
A method for treating at least one first material layer including siloxane bonds, wherein at least one surface can be interlocked with a surface of a second material layer by direct bonding, the method including: at least one forced diffusion at a temperature greater than or equal to 30° C., at least in the first material layer, of chemical species including at least one pair of free electrons and at least one labile proton; and converting at least one portion of the siloxane bonds into silanol bonds in at least one portion of the first material layer extending from the surface to a depth greater than or equal to approximately 10 nm.