Wafer Self-Alignment via Liquid Surface Tension
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Solution Overview
Problem
Existing stacked semiconductor device manufacturing processes are difficult to execute due to the need for precise alignment of wafers, which complicates the stacking process.
Innovation Solution
A method involving the formation of grooves on wafers to create demarcated areas, where a liquid is used to facilitate self-alignment under surface tension, followed by evaporation to secure the wafers in intimate contact, utilizing limiters to prevent shifting and connecting electrodes for stable bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional stacking processes are used to stack many devices at a time, then productivity is improved, but manufacturing precision deteriorates due to the difficulty of positioning wafers in accurate alignment
Solution Approach 1:
A liquid is introduced as an intermediary substance between the two wafers to enable self-alignment. The liquid fills the gaps and allows surface tension forces to act uniformly across the wafer surfaces, automatically positioning them in accurate alignment without requiring complex external positioning mechanisms.
Solution Approach 2:
The wafers perform self-alignment through the liquid medium. By placing the wafers facing each other with liquid in between, the system utilizes surface tension and capillary forces to automatically position the wafers in correct alignment without external intervention or complex positioning equipment.
2Manufacturing precision
If wafers are positioned with high alignment accuracy using conventional methods, then manufacturing precision is improved, but device complexity increases due to the difficulty of the positioning process
Solution Approach 1:
The liquid acts as a mediator that simplifies the positioning process. Instead of using complex mechanical positioning systems or precision alignment equipment, the liquid enables automatic alignment through physical forces, dramatically reducing process complexity while maintaining high precision.
Solution Approach 2:
The invention replaces complex mechanical positioning systems with a liquid-based self-alignment mechanism. Surface tension and capillary forces substitute for mechanical alignment tools, reducing the complexity of the positioning process while achieving accurate wafer alignment.
3Ease of operation
If a large quantity of liquid is supplied to demarcated areas, then ease of operation is improved, but manufacturing precision deteriorates due to liquid overflow affecting alignment
Solution Approach 1:
The demarcated areas on the wafer surfaces have specific local properties that control liquid distribution. The grooves and demarcated regions are designed to confine the liquid locally, ensuring it remains within specific boundaries and prevents overflow while maintaining sufficient liquid for self-alignment.
Solution Approach 2:
The invention controls the volume and distribution parameters of the liquid precisely. By adjusting the liquid quantity to match the specific geometry of the demarcated areas and utilizing capillary pressure relationships, the system maintains optimal liquid levels that enable self-alignment without causing overflow that would disrupt alignment.
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 simplifies the alignment and stacking of wafers by leveraging surface tension for self-alignment and evaporation for secure contact, reducing the complexity and difficulty of the process.
Implementation Method 1
bringing respective central positions of the facing demarcated areas of the wafers into self-alignment with each other under the surface tension of the liquid sandwiched between the facing demarcated areas
Implementation Method 2
charging the wafers that have been superposed one over the other into a decompression chamber, and evacuating the decompression chamber to reduce the pressure therein for evaporating the liquid
Implementation Method 3
evacuating the decompression chamber to reduce the pressure therein for evaporating the liquid
Data Source
AI summary
A stacked wafer assembly is made by forming a grid of grooves corresponding to projected dicing lines in a face side of each of two wafers, thereby forming demarcated areas on the face side of each of the two wafers. One of the wafers is installed with demarcated areas face upwardly, and thereafter liquid is supplied to the demarcated areas in a quantity just enough to stay on upper surfaces of the demarcated areas without overflowing. The other wafer is placed over the one wafer with demarcated areas of the other wafer facing the respective demarcated areas of the one wafer, thereby bringing respective central positions of the facing demarcated areas of the wafers into self-alignment with each other under the surface tension of the liquid sandwiched between the facing demarcated areas. The liquid is removed to bring the wafers into intimate contact with each other.