Micro-LED Transfer With Pitch Scaling and Localized Release
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Solution Overview
Problem
The high fabrication cost of micro-LED displays is due to the complex semiconductor processes required for growing small micro-LEDs, and the challenge of localized detachment and attachment of micro-LEDs during the transfer process is not efficiently addressed.
Innovation Solution
A method involving pitch scaling and localized release mechanisms, such as using a release layer activated by light or mechanical deflection, to selectively transfer micro-LEDs from a growth substrate to a back-plane substrate, allowing reuse of the growth substrate for multiple displays.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If micro-LEDs are grown on a growth substrate in a high-density array, then the quantity of micro-LEDs produced increases, but the complexity of selectively transferring individual micro-LEDs to specific pixel locations increases
Solution Approach 1:
The transfer process is segmented into distinct phases: first, all micro-LEDs are grown in a high-density array on the growth substrate; second, the entire array is transferred to a carrier substrate; third, specific micro-LEDs are selectively released from the carrier substrate to pixel locations using a release layer. This segmentation allows high-volume production while simplifying the selective transfer operation.
Solution Approach 2:
A carrier substrate with a release layer is introduced as an intermediary between the growth substrate and the final display substrate. The release layer acts as a temporary bonding agent that holds all micro-LEDs during transport but can be selectively removed to release individual micro-LEDs at target locations, thereby simplifying the selective transfer process.
2Productivity
If pitch scaling is used to transfer micro-LEDs from a first pitch to a second pitch, then multiple displays can be produced from a single growth substrate, but the alignment precision requirements increase
Solution Approach 1:
The micro-LEDs are pre-positioned in a high-density array on the growth substrate with precise spacing before transfer. The carrier substrate and release layer are prepared in advance with alignment features. This preliminary preparation ensures that when pitch scaling occurs, the micro-LEDs maintain accurate alignment with pixel locations across multiple displays.
3Ease of operation
If a release layer is used to hold micro-LEDs on a carrier substrate, then selective release and transfer becomes possible, but the fabrication process complexity increases
Solution Approach 1:
The release layer's bonding properties are changed through parameter modification - specifically, its adhesion strength is tuned to be strong enough to hold micro-LEDs during transfer but weak enough to allow selective release. This is achieved by controlling the release layer's material composition, thickness, or thermal/chemical properties, enabling selective release without adding complex fabrication steps.
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 reduces fabrication costs and simplifies the process by enabling efficient transfer of micro-LEDs to a back-plane substrate while maintaining alignment accuracy, facilitating the production of multiple displays from a single growth substrate.
Implementation Method 1
activating the release layer to generate an activated release layer at the pixel locations of the micro-LED display
Implementation Method 2
deflecting the membrane at the pixel locations of the micro-LED display to locally release the micro-LEDs from the carrier substrate
Data Source
AI summary
Fabricating a micro light emitting diode (micro-LED) display may include transferring micro-LEDs from a growth substrate to a two-dimensional array on a back-plane substate. The two-dimensional array on the back-plane substrate has a spacing between micro-LEDs, which is larger than the spacing between micro-LEDs on the growth substrate.