Monolithic Micro LED Wafer Transfer for Yield and Cost
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Solution Overview
Problem
Current micro-LED display fabrication and assembly methods are costly and inefficient, particularly for larger displays, due to high defect density and the need for sequential transfer of individual micro LEDs, which limits manufacturing yield and increases equipment complexity.
Innovation Solution
The method involves transferring monolithic red, green, and blue micro LEDs from a source wafer to a display backplane using wafer-to-wafer bonding equipment, enabling multiple micro LEDs per color per pixel and reducing defect density through redundancy, while using nanowire LEDs with a superlambertian radiation pattern for improved light emission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If sequential transfer of individual micro LEDs is used, then manufacturing cost is reduced for small displays, but manufacturing yield decreases and equipment complexity increases for larger displays
Solution Approach 1:
The patent segments the micro LED array into modular blocks that can be transferred in groups rather than individually. This segmentation allows for more efficient handling and transfer processes, improving yield while maintaining cost-effectiveness for larger displays.
Solution Approach 2:
The patent introduces an intermediary carrier substrate that temporarily holds multiple micro LED blocks during the transfer process. This intermediary enables batch transfer operations, reducing equipment complexity and improving manufacturing yield compared to direct individual transfer methods.
2Ease of manufacture
If sequential transfer of individual micro LEDs is used, then manufacturing cost is reduced for small displays, but device complexity increases for larger displays
Solution Approach 1:
The patent merges multiple micro LED transfer operations into a single batch process by transferring blocks of LEDs simultaneously. This consolidation reduces equipment complexity by eliminating the need for complex individual positioning and transfer mechanisms required for sequential single-LED transfer.
Solution Approach 2:
The patent performs preliminary arrangement of micro LEDs into organized blocks on the carrier substrate before the actual transfer to the display. This preliminary organization simplifies the subsequent transfer process and reduces the complexity of transfer equipment needed for larger displays.
3Illumination intensity
If monolithic micro LEDs are used, then color gamut is improved, but defect density increases
Solution Approach 1:
The patent applies local quality by using monolithic micro LEDs specifically for the red, green, and blue subpixels where high color purity is critical, while accepting that defect density may be higher in these premium components. The block transfer method provides redundancy to compensate for these defects.
Solution Approach 2:
The patent uses excessive action by transferring multiple micro LED blocks per pixel, providing redundancy that exceeds the minimum single-LED requirement. This allows selection of defect-free LEDs from the transferred blocks, ensuring high reliability while maintaining the color gamut benefits of monolithic LEDs.
4Reliability
If multiple micro LEDs per color per pixel are used, then defect density is reduced through redundancy, but manufacturing complexity increases
Solution Approach 1:
The patent merges multiple micro LED transfers into a single block transfer operation. By transferring blocks containing multiple LEDs of the same color simultaneously, the system achieves redundancy for defect compensation while keeping the manufacturing process simple and avoiding the complexity of individual LED handling.
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 manufacturing costs, increases yield, and achieves lower power consumption, resulting in micro-LED displays that consume two-fold less power than OLEDs, extending battery life in mobile devices by approximately 8 hours and offering improved performance in energy efficiency, color gamut, and environmental stability.
Implementation Method 1
irradiating the adhesive layer through the glass carrier substrate with a UV light source to release and transfer the portion of the plurality of LED pixel elements
Data Source
AI summary
Micro light-emitting diode (LED) displays, and fabrication and assembly of micro LED displays, are described. In an example, a pixel element for a micro-light emitting diode (LED) display panel includes a blue color nanowire or nanopyramid LED above a first nucleation layer above a substrate, the blue color nanowire or nanopyramid LED including a first GaN core. A green color nanowire or nanopyramid LED is above a second nucleation layer above the substrate, the green color nanowire or nanopyramid LED including a second GaN core. A red color nanowire or nanopyramid LED is above a third nucleation layer above the substrate, the red color nanowire or nanopyramid LED including a GaInP core.