Self-aligned wafer bonding via liquid surface tension
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Solution Overview
Problem
Conventional wafer bonding techniques face challenges in achieving high precision alignment, especially when both wafers are opaque, with alignment precision typically ranging from 5 to 10 micrometers, which is insufficient for modern feature scales, and there is a need for alignment within 100 nanometers or less.
Innovation Solution
A self-aligned wafer bonding technique utilizing liquid surface tension to align complementary hydrophilic areas of two wafers, where water droplets are used to separate the wafers and evaporate, allowing low-temperature eutectic metal alloy bonding once aligned.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional visual alignment techniques are used, then the bonding process can be performed with simple equipment, but the alignment precision deteriorates to 5-10 micrometers which is insufficient for modern feature scales
Solution Approach 1:
The patent introduces water droplets as an intermediary substance between the two wafers. The droplets create capillary forces that automatically pull the wafers into precise alignment when the hydrophilic features contact the liquid interface, achieving sub-100 nanometer alignment precision without complex alignment equipment
Solution Approach 2:
The alignment process is made self-aligning through the chemical properties of the wafer surfaces. The hydrophilic areas naturally attract the water droplets, and the capillary forces generated by the liquid automatically position the wafers relative to each other, eliminating the need for external alignment systems
2Adaptability or versatility
If both wafers are opaque, then the wafer bonding can be performed with standard materials, but the alignment precision deteriorates because visual alignment techniques cannot be effectively used
Solution Approach 1:
The patent replaces optical/mechanical alignment systems with a chemical-physical mechanism. Instead of using microscopes or mechanical positioning systems that require visual access, the invention uses capillary forces generated by water droplets interacting with hydrophilic surface features to achieve automatic alignment, which works equally well with opaque materials
Solution Approach 2:
The patent changes the surface energy parameters of the wafer surfaces by creating hydrophilic areas with specific chemical properties. This parameter change enables the surfaces to interact with water droplets in a controlled manner, generating the capillary forces necessary for precise alignment regardless of the bulk material's opacity
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 precise alignment of wafer features to within 100 nanometers or less and forms a strong bond using a low-temperature eutectic metal alloy, overcoming the limitations of conventional alignment techniques.
Implementation Method 1
self-alignment technique utilizing liquid surface tension to align complimentary hydrophilic areas of two wafers
Implementation Method 2
hydrophobic areas surrounding the hydrophilic areas
Implementation Method 3
Once aligned the liquid is evaporated and the wafers are bonded
Data Source
AI summary
A wafer article includes a substrate, two or more hydrophilic areas disposed on the substrate, hydrophobic areas surrounding the hydrophilic areas, and a eutectic bonding material disposed on the substrate. A wafer apparatus including two wafers having complimentary hydrophilic regions and eutectic bonding material is disclosed and a method of forming a bonded wafer articles is disclosed.