Selective Micro Device Transfer Using Donor-Receiver Force Switching
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Solution Overview
Problem
Current methods for selectively transferring micro devices from a donor substrate to a receiver substrate lack precision and efficiency, often resulting in the transfer of unwanted devices due to uniform bonding forces, which hinders the formation of operational systems like LED displays or sensors.
Innovation Solution
A method involving the alignment of donor and receiver substrates, followed by the modulation of donor and receiver forces using techniques such as laser lift-off, heating, adhesive application, mechanical grip, or electrostatic attraction to selectively transfer micro devices, ensuring that only intended devices are transferred to the receiver substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If uniform bonding forces are applied to all micro devices, then the transfer process is simple, but unwanted devices are transferred along with intended devices
Solution Approach 1:
The patent applies local quality by creating spatially varying bonding forces across the donor substrate. Different regions of the substrate experience different force magnitudes, allowing selective transfer of micro devices from high-force regions while leaving devices in low-force regions on the donor substrate. This resolves the contradiction by maintaining process simplicity while achieving transfer selectivity through localized force modulation.
Solution Approach 2:
The patent implements dynamics by making the bonding force time-dependent and controllable during the transfer process. The force magnitude can be dynamically adjusted to different levels at different stages, enabling selective detachment of intended devices while maintaining attachment of unwanted devices. This dynamic control allows the system to transition from a static uniform force state to a controlled selective transfer state.
2Reliability
If strong bonding force is used to ensure device attachment, then device transfer reliability is high, but selectivity control becomes difficult
Solution Approach 1:
The patent applies segmentation by dividing the donor substrate into multiple regions with different bonding force characteristics. Each region can be independently controlled to have appropriate force strength for its intended function (transfer or retain). This segmentation allows the system to maintain strong bonding where needed for reliability while creating weaker bonding zones for selective release, managing the complexity through regional decomposition.
Solution Approach 2:
The patent implements parameter changes by varying the bonding force parameter across different spatial locations and time points during the transfer process. The force magnitude, direction, or duration can be changed to achieve selective device release. This parameter modulation enables the system to switch between strong bonding (for reliability) and weak bonding (for selectivity) states as needed.
3Productivity
If all micro devices are transferred to the receiver substrate, then the transfer efficiency is high, but the precision of selecting specific devices is lost
Solution Approach 1:
The patent applies periodic action by implementing cyclic force modulation during the transfer process. The bonding force is applied periodically or in pulses, allowing intended devices to be transferred during high-force phases while unwanted devices remain attached during low-force phases. This periodic variation in force enables selective transfer while maintaining high overall transfer efficiency through repeated transfer cycles.
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 allows for precise and selective transfer of micro devices, improving the assembly of complex systems by minimizing the transfer of non-intended devices and enhancing the integration of micro devices into receiver substrates, thereby increasing the efficiency and reliability of device integration.
Implementation Method 1
Some embodiments further comprise weakening the donor force using laser lift off.
Implementation Method 2
Some embodiments further comprise weakening the donor force by heating an area of the donor substrate.
Implementation Method 3
In some embodiments the receiver force is generated by electrostatic attraction between the selected micro devices and the receiver substrate.
Implementation Method 4
In some embodiments the receiver force is generated by mechanical grip.
Implementation Method 5
In some embodiments the receiver force is generated by an adhesive layer positioned between the selected micro devices and the receiver substrate.
Data Source
AI summary
A method of selectively transferring micro devices from a donor substrate to contact pads on a receiver substrate. Micro devices being attached to a donor substrate with a donor force. The donor substrate and receiver substrate are aligned and brought together so that selected micro devices meet corresponding contact pads. A receiver force is generated to hold selected micro devices to the contact pads on the receiver substrate. The donor force is weakened and the substrates are moved apart leaving selected micro devices on the receiver substrate. Several methods of generating the receiver force are disclosed, including adhesive, mechanical and electrostatic techniques.