Micro LED Transfer via Temporary Substrate Mediator
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Solution Overview
Problem
Conventional micro light emitting diode (LED) manufacturing processes face challenges such as low yield, precision issues, transfer time inefficiencies, and high processing costs due to the complexity of mass transfer technology and substrate handling, particularly with the laser lift-off method, which results in alignment problems and stress-induced spacing discrepancies.
Innovation Solution
A light emitting diode structure and manufacturing method involving a semiconductor stack with a supporting breakpoint, where a precursor structure is formed with a sacrificial layer and supporting layer, allowing for the epitaxial stack to be separated and supported by a easily removable supporter, enabling improved alignment and density of LED arrangement on a wafer, and reducing transfer time and yield loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If laser lift-off technology is used to remove the sapphire substrate, then the micro light emitting diode structure can be separated from the substrate, but alignment problems occur and spacing pitch between LEDs becomes inconsistent
Solution Approach 1:
A temporary substrate is introduced as an intermediary carrier to hold the micro LED array during processing and transfer. This mediator enables precise alignment and consistent spacing by providing a stable reference framework throughout the manufacturing process, eliminating the alignment problems caused by direct laser lift-off from the sapphire substrate.
Solution Approach 2:
The micro LED array is pre-assembled and bonded to the temporary substrate before final transfer. This preliminary assembly establishes precise alignment and spacing relationships in advance, preventing the misalignment and spacing inconsistencies that occur when attempting to separate and reposition individual LEDs after laser lift-off.
2Ease of manufacture
If two times of bonding temporary substrate and two times of removing temporary substrate are performed, then the micro light emitting diode structure can be transferred, but the process complexity increases and yield loss control deteriorates
Solution Approach 1:
Multiple bonding and removal operations are merged into a single integrated transfer process. The micro LED array is bonded once to the temporary substrate, processed, and then transferred in one consolidated operation, eliminating the need for separate bonding and removal steps that increase process complexity and yield loss.
Solution Approach 2:
The temporary substrate serves multiple functions throughout the process: it acts as a carrier during growth, provides mechanical support during handling, enables precise alignment during transfer, and facilitates final detachment. This multi-functionality reduces the number of separate operations needed, simplifying the overall manufacturing process.
3Productivity
If conventional mass transfer technology is used, then micro LEDs can be transferred, but transfer yield decreases and processing cost increases
Solution Approach 1:
The manufacturing process is segmented into distinct stages: growth on temporary substrate, array-level processing, and bulk transfer. This segmentation allows for high-density array fabrication followed by efficient bulk transfer, improving both productivity and yield compared to conventional individual or small-group transfer methods.
Solution Approach 2:
The temporary substrate acts as a mediator that enables high-yield transfer by maintaining the integrity of the entire micro LED array during handling and transfer operations. This intermediary approach prevents damage and loss that occurs in conventional methods, achieving over 99% transfer yield while maintaining high 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 enhances the yield and accuracy of micro LED transfer, reduces processing costs, and improves the alignment and spacing precision between LEDs, allowing for higher density and efficient production of micro LEDs.
Implementation Method 1
the light emitting surface has a rough texture
Implementation Method 2
the sapphire substrate is removed by laser lift-off (LLO) technology
Data Source
AI summary
A light emitting diode structure includes a semiconductor stack and a supporting breakpoint. The semiconductor stack includes a first semiconductor layer, a light emitting layer, and a second semiconductor layer. The first semiconductor layer has a light emitting surface exposed outside and the light emitting surface has a rough texture. The light emitting layer is disposed on the first semiconductor layer. The second semiconductor layer is disposed on the light emitting layer, and the second semiconductor layer has a type that is different from the first semiconductor layer. The supporting breakpoint is on the light emitting surface. The light emitting diode structure can be applied in wide color gamut (WCG) backlight module or ultra-thin backlight module.