Direct Bonding Edge Thinning for Defect Prevention
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Solution Overview
Problem
Direct bonding of substrates often results in defects at the edges due to adiabatic expansion caused by the bonding wave, particularly in hydrophilic bonding, which can be exacerbated by high overpressure and rapid wave propagation, and existing solutions require modifying atmospheric conditions that are not always feasible in standard bonding machines.
Innovation Solution
Thinning the edges of one substrate on a significant portion of its circumference to reduce rigidity and allow deformation during bonding, enabling the substrate to absorb the stress from the bonding wave without causing defects, while maintaining bonding at ambient temperature and pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If bonding is performed at ambient temperature and pressure in standard machines, then the bonding process is simple and accessible, but bonding defects appear at the edges due to adiabatic expansion from the bonding wave
Solution Approach 1:
The edge portions of the substrates are thinned in advance before the bonding operation. This preliminary action reduces the rigidity of the edges, allowing them to deform and absorb the stress from the bonding wave, thereby preventing edge defects while maintaining ambient temperature and pressure bonding conditions
2Reliability
If the edges of substrates are thinned, then edge defects are prevented by allowing substrate deformation, but additional manufacturing steps are required
Solution Approach 1:
The physical parameter of the substrate edges is changed by reducing their thickness. This parameter change modifies the mechanical properties of the edges, making them more compliant and capable of absorbing bonding wave stress, thereby preventing defects without requiring complex bonding process modifications
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 effectively prevents edge defects during direct bonding by allowing the substrate to deform and absorb stress, ensuring secure bonding without the need for altering atmospheric conditions, thus maintaining the integrity of the bonding process in standard machine environments.
Implementation Method 1
When the bonding wave comes at the edges of the substrates, an adiabatic expansion occurs and can cause the appearance of defects at the edges of the substrates... This discharge generates an overpressure of about two atmospheres at the bonding wavefront
Implementation Method 2
The molecular bonding is induced by all the electronic interaction attractive forces between the atoms or molecules of the two materials to be bonded (Van der Waals forces)
Implementation Method 3
In such a hydrophilic bonding, the silanol bonds (Si—OH) of surfaces and a water film present between both substrates enable hydrogen bonding interactions stronger than Van der Waals forces
Data Source
AI summary
A method for direct bonding between at least a first and a second substrate, each of the first and second substrates containing a first and a second main surface, the method including: a first thinning of the edges of the first substrate over at least one portion of the circumference of the first substrate, at the first main surface of the first substrate; and placing the second main surface of the first substrate in contact with the second main surface of the second substrate such that a bonding wave propagates between the first and second substrates, securing the first and second substrates to one another by direct bonding such that portions of the second main surface of the first substrate located below the thinned portions of the first main surface of the first substrate are secured to the second substrate.