Shear-Assisted Elastomeric Stamp Transfer Printing
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Solution Overview
Problem
Conventional vacuum grippers struggle with handling ultra-thin, fragile, or small semiconductor chips, and existing dry transfer printing techniques face challenges with high-throughput and accuracy, especially on low-tack surfaces and non-smooth substrates, due to unstable delamination rates and low transfer yields.
Innovation Solution
The method employs shear offset printing, which involves mechanical deformation of the transfer stamp to increase delamination rates and maintain a constant delamination rate, using a composite stamp with a deformable layer and a rigid backing, optimized with relief features and controlled air pressure to achieve high transfer yields and accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional vacuum grippers are used to handle semiconductor chips, then handling capability is provided, but they cannot economically handle ultra-thin, fragile, or too small chips
Solution Approach 1:
The patent replaces the mechanical vacuum suction system with a shear-assisted elastomeric stamp transfer system. The elastomeric stamp uses elastic deformation and shear stress to pick up and transfer semiconductor elements, eliminating the need for vacuum grippers and enabling handling of ultra-thin, fragile, or small chips that cannot be handled by conventional vacuum methods.
Solution Approach 2:
The patent changes the fundamental operating parameters from vacuum pressure to shear stress and elastic deformation. By controlling the shear offset distance and the degree of elastomeric deformation, the system achieves selective pickup and release of semiconductor elements, providing versatile handling capability while maintaining economic efficiency through a simpler mechanical system.
2Productivity
If dry transfer printing is used for massively parallel assembly, then assembly throughput is improved, but transfer yield and placement accuracy deteriorate due to unstable delamination rates
Solution Approach 1:
The patent implements feedback control of the delamination rate by dynamically adjusting the shear offset distance during the stamp withdrawal process. Sensors monitor the delamination progress and provide feedback to the control system, which adjusts the shear offset in real-time to maintain a constant delamination rate, ensuring both high transfer yield and precise placement accuracy while maintaining massively parallel assembly throughput.
Solution Approach 2:
The patent transforms the static delamination process into a dynamic controlled process by varying the shear offset distance as a function of time or withdrawal position. This dynamic adjustment allows the system to adapt to changing adhesion conditions during delamination, maintaining optimal transfer yield and placement accuracy throughout the entire transfer process while preserving high assembly throughput.
3Loss of time
If high delamination rates are used in transfer printing, then processing time is reduced, but transfer yield and accuracy are sacrificed
Solution Approach 1:
The patent employs dynamic control of the shear offset distance during stamp withdrawal to maintain a constant delamination rate regardless of the overall withdrawal speed. By adjusting the shear offset in real-time based on feedback from delamination monitoring, the system achieves high delamination rates that reduce processing time while simultaneously maintaining transfer yield and accuracy above 95%.
Solution Approach 2:
The patent changes the control parameter from fixed shear offset to dynamically varying shear offset as a function of delamination progress. This parameter change enables the system to operate at high delamination rates for reduced processing time while maintaining the precision and yield characteristics of slow, controlled delamination through real-time parameter adjustment.
4Force
If elastomeric stamp adhesion forces are increased by slowing delamination rate, then pickup capability is improved, but transfer time increases and throughput decreases
Solution Approach 1:
The patent uses feedback control to maintain optimal adhesion forces during the transfer process. By monitoring delamination progress and adjusting the shear offset in real-time, the system maintains sufficient adhesion forces for reliable pickup and transfer while operating at higher delamination rates that improve throughput, eliminating the need to slow down the process to maintain adhesion.
Solution Approach 2:
The patent transforms the static adhesion force requirement into a dynamic process where the shear offset is continuously adjusted to maintain optimal adhesion conditions throughout the transfer. This dynamic approach allows the system to achieve both strong effective adhesion for high transfer yield and high delamination rates for improved throughput, resolving the contradiction between force and productivity.
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 significantly increases transfer yields and delamination rates, achieving greater than 95% transfer efficiency and maintaining high accuracy, even on low-tack surfaces, while reducing processing time and improving printing efficiency.
Implementation Method 1
dry transfer printing tools rely on surface adhesion forces to control the pickup and release of the semiconductor devices
Implementation Method 2
The elastomeric stamp is offset a horizontal distance relative to the receiving surface, thereby generating a mechanical deformation in at least a portion of the pattern of relief features
Data Source
Figure 1A~1D
Figure 2A~2B
Figure 3
AI summary
Provided are methods and devices for transfer printing of semiconductor elements to a receiving surface. In an aspect, the printing is by conformal contact between an elastomeric stamp inked with the semiconductor elements and a receiving surface, and during stamp removal, a shear offset is applied between the stamp and the receiving surface. The shear-offset printing process achieves high printing transfer yields with good placement accuracy. Process parameter selection during transfer printing, including time varying stamp-backing pressure application and vertical displacement, yields substantially constant delamination rates with attendant transfer printing improvement.