Curved Wafer Chuck Bonding to Minimize Air Bubbles in SoIC Packaging
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Solution Overview
Problem
The increasing complexity of integrated circuit packages, particularly System-on-Integrated-Chips (SoIC), poses challenges in efficiently bonding multiple component dies with different technologies and functions, leading to manufacturing inefficiencies and yield loss due to trapped air bubbles during the bonding process.
Innovation Solution
The use of a wafer chuck with a curved surface to warp the wafer and device dies into contact, followed by an annealing process to form dielectric-to-dielectric bonds, encapsulation, and redistribution lines, minimizing air bubble formation and enhancing bonding efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple component dies are integrated in the same package to achieve more functions, then the device functionality and system integration are improved, but the manufacturing complexity and difficulty of bonding increase
Solution Approach 1:
The bonding process is segmented into multiple controlled stages: initial contact at center point, gradual expansion of contact area, and final complete bonding. This segmentation allows complex multi-die packaging to be managed through systematic, repeatable steps rather than attempting to bond all dies simultaneously
Solution Approach 2:
The wafer surface is pre-treated with oxygen plasma to create a reactive surface that enhances bonding capability before the actual bonding process. Additionally, the bonding interface is prepared by ensuring proper alignment and initial contact conditions, which facilitates subsequent bonding of multiple component dies with different technologies
2Ease of manufacture
If conventional bonding processes are used to bond component dies, then the bonding process is simple to implement, but air bubbles are trapped during bonding leading to yield loss
Solution Approach 1:
The bonding process utilizes a curved trajectory approach where the wafer surface contacts the component dies progressively from a center point outward, similar to a spherical expansion pattern. This curved bonding front prevents air entrapment by ensuring air is continuously pushed outward rather than being trapped in pockets, while maintaining a relatively simple single-pass bonding operation
Solution Approach 2:
The natural tendency of air to be trapped during bonding is converted into a beneficial outward flow pattern. By controlling the bonding interface to expand from a center point, the air is systematically directed outward toward the edges where it can escape, transforming the potential harm of air entrapment into an efficient air evacuation mechanism
3Manufacturing precision
If the wafer surface is flat during bonding, then the alignment is easy to maintain, but air bubbles are trapped between the wafer and device dies
Solution Approach 1:
Instead of using a flat wafer surface, the bonding interface is designed to progress along a curved trajectory from the center point outward. This curvature ensures that the wafer surface maintains consistent alignment with the component dies while simultaneously preventing air bubble formation by directing air outward during the bonding progression
4Adaptability or versatility
If more component dies are bonded together, then the system integration and functionality are enhanced, but the manufacturing time and process complexity increase
Solution Approach 1:
Multiple component dies with different technologies and functions are bonded simultaneously in a single integrated process step rather than sequentially. The curved surface bonding method enables all dies to be bonded in one operation, merging what would otherwise be multiple separate bonding steps into a single efficient process
Solution Approach 2:
All component dies are positioned and pre-aligned on the wafer surface before the bonding process begins. This preliminary arrangement, combined with the curved bonding approach, allows multiple dies to be bonded simultaneously without requiring complex real-time adjustments during the bonding process, thereby maintaining high manufacturing efficiency
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 reduces the number of trapped air bubbles, improving the yield and manufacturing efficiency of integrated circuit packages by ensuring robust bonding between component dies.
Implementation Method 1
The wafer chuck may have a curved surface. The curved surface may have a frowning curve profile or a smiling curve profile.
Implementation Method 2
performing an annealing process to bond the first dielectric layer to the second dielectric layer
Data Source
AI summary
A method includes attaching a wafer to a wafer chuck having a curved surface. The method further includes placing a device die on the wafer, such that a first dielectric layer of the device die is in contact with a second dielectric layer of the wafer, and performing an annealing process to bond the first dielectric layer to the second dielectric layer. The method further includes encapsulating the device die with an encapsulating material, forming redistribution lines overlapping the encapsulating material and the device die, and sawing the encapsulating material to form a plurality of packages.