Compacting Roller for Ultrathin Die Bonding
Solution Overview
Problem
Ultrathin semiconductor wafers experience warping and void formation during the pick and place process due to vacuum forces, leading to delamination and incomplete bonding with substrates, which existing technologies struggle to address effectively without costly and complex bonders and stringent process control.
Innovation Solution
A method involving the use of a compacting roller with a soft surface layer to apply a controlled downward force on ultrathin dies before annealing, increasing the bonded area and reducing voids by promoting contact bonding between the die and substrate, utilizing a compacting roller with a Shore 00 hardness of 30-80 and applying forces up to 1.5 kg to ensure proper contact without damaging the wafers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If vacuum pick and place is used to handle ultrathin wafers, then automated assembly is achieved, but the vacuum forces cause warping and void formation leading to delamination
Solution Approach 1:
The patent applies preliminary action by performing the compacting step immediately after pick-and-place and before annealing. This timing ensures that voids are eliminated while the die is still relatively cool and manageable, preventing delamination before the bonding process is complete. The compacting roller is applied in the precise sequence needed to address vacuum-induced warping without compromising the subsequent annealing process.
Solution Approach 2:
The compacting roller serves as an intermediary tool between the pick-and-place process and annealing. It mediates the transition by applying controlled pressure to eliminate voids caused by vacuum handling, bridging the gap between automated assembly and thermal bonding without requiring complex modifications to either process.
2Manufacturing precision
If compacting force is applied to eliminate voids, then bonding area is increased, but excessive force may damage the ultrathin die
Solution Approach 1:
The patent applies parameter changes by carefully controlling the compacting force within a specific range (0.5-2.0 kgf) and adjusting the Shore 00 hardness of the roller surface (20-90). These parameter optimizations ensure sufficient pressure to eliminate voids and maximize bonding area while remaining below the threshold that would damage ultrathin die structures. The force and hardness parameters are tuned based on die thickness and material properties.
Solution Approach 2:
The compacting roller with its specific Shore 00 hardness range (20-90) provides localized quality control. The roller's surface properties are specifically engineered to distribute pressure evenly across the die surface, applying exactly the right amount of force locally to eliminate voids without concentrating stress that could cause die fracture. This local quality control is critical for handling ultrathin die where uniform pressure distribution is essential.
3Reliability
If soft surface layer with Shore 00 hardness of 30-80 is used, then contact bonding is promoted, but material selection becomes more constrained
Solution Approach 1:
The patent applies parameter changes by defining a specific Shore 00 hardness range (30-80) for the compacting roller surface layer. This parameter specification balances the need for sufficient softness to conform to die surface irregularities and promote contact bonding, while maintaining enough structural integrity to apply effective compacting force. The hardness parameter is optimized to work across different die materials and thicknesses within the ultrathin range.
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 approach enhances bonding yields by increasing the bonded area from 50% to nearly 100% of the interface, reducing voids and preventing delamination, while being cost-effective and reliable, and further strengthens the bond through annealing.
Implementation Method 1
compact the die to the substrate using a downward force on at least the die to increase a bonded area between the die and the upper surface of the substrate
Implementation Method 2
the compacting roller has a soft surface layer that engages with the die and the upper surface of the substrate, the soft surface layer has a Shore 00 hardness of greater than approximately 30 and less than approximately 80
Implementation Method 3
annealing of the die and substrate
Data Source
AI summary
Methods and apparatus for increasing a bonded area between an ultrathin die and a substrate. In some embodiments, the method may include cleaning the die and the substrate, placing the die on an upper surface of the substrate, compacting the die to the substrate using a downward force of at least one compacting roller on the die and the upper surface of the substrate to increase a bonded area between the die and the upper surface of the substrate, and annealing the die and the substrate. The compacting roller has a soft surface layer that engages with the die and the upper surface of the substrate. The soft surface layer has a Shore hardness of greater than approximately 30 and less than approximately 80. In some embodiments, the substrate and/or the compacting roller may rotate during contact with each other.