Micro Device Transfer Using Self-Curing Photo-Bonding
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Solution Overview
Problem
Existing methods for transferring micro devices from a donor substrate to a receiver substrate are complex, require intricate mechanical structures, and struggle with controlling spot size for localized heating or epoxy curing, especially as device size miniaturizes and density increases.
Innovation Solution
A method involving a cartridge substrate with bonding materials that uses light to cure the photo-sensitive layer between micro devices and the receiver substrate, utilizing sidewall reflectors to focus light for precise bonding, and employing a sacrificial release layer for efficient transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If localized heating or external light source is used for epoxy curing, then micro devices can be transferred from donor substrate to receiver substrate, but spot size control is difficult causing adjacent devices to cure and transfer undesiredly
Solution Approach 1:
The micro-LEDs themselves serve as the light source for curing the photo-sensitive layer. By activating the micro-LEDs, they emit light that cures the photo-sensitive layer in immediate proximity, enabling self-service bonding without external light sources. This eliminates the spot size control issue since the light source is inherently localized to each micro-LED's position.
Solution Approach 2:
A photo-sensitive layer is introduced as an intermediary material between the micro-LEDs and the receiver substrate. This layer is cured by light from the micro-LEDs to create a strong bond, mediating the transfer process and enabling precise localized bonding without affecting adjacent devices.
2Productivity
If mechanical, thermal, or electrostatic techniques are used to generate receiver force, then micro devices can be transferred, but complex mechanical structures are required
Solution Approach 1:
The patent replaces complex mechanical transfer structures with a photochemical bonding mechanism. Instead of using mechanical, thermal, or electrostatic techniques to generate receiver force, the system uses light-emitting micro-LEDs to cure a photo-sensitive layer, creating bonds through photochemical reactions. This substitution eliminates the need for intricate mechanical apparatus while maintaining transfer efficiency.
Solution Approach 2:
The invention changes the bonding mechanism from mechanical/thermal/electrostatic forces to photochemical bonding. By changing the parameter of how bonding force is generated (from physical forces to light-induced chemical reactions), the system achieves simple transfer without complex mechanical structures.
3Manufacturing precision
If external light source is used for curing, then epoxy photo curing can be achieved, but control over stigmation and spot size is limited especially when device size is miniaturized
Solution Approach 1:
Each micro-LED serves as its own light source for curing the photo-sensitive layer in its immediate vicinity. This self-service approach eliminates the need for external light sources and the associated stigmation control problems. The light emission is inherently aligned with the micro-LED position, providing automatic stigmation and precise spot size control matching the miniaturized device dimensions.
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
Enables efficient, precise, and simplified transfer of micro devices with minimal light leakage, reducing the need for complex mechanical structures and heat, while maintaining control over the bonding process.
Implementation Method 1
curing the photo-sensitive layer in between the selected set of micro devices and the system substrate by light emitted by the selected micro devices
Implementation Method 2
sidewall reflectors to reflect the light back toward the micro device
Data Source
AI summary
A method of selectively transferring micro devices from a donor substrate to contact pads on a receiver substrate. The method may comprise: providing a donor substrate comprising the plurality of micro devices, transferring the plurality of micro devices to an intermediate substrate, aligning a selected set of micro devices on the intermediate substrate proximal to the system substrate, providing a photo-sensitive layer between the selected set of micro devices and the system receiver; turning on the selected micro devices, curing the photo-sensitive layer in between the selected set of micro devices and the system substrate by light emitted by the selected micro devices; and bonding the selected set of micro devices to the corresponding contact pads on the system substrate.