AgAu Reflective Contact Layer for Accurate Micro-LED Self-Assembly
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Solution Overview
Problem
Micro-LED displays face challenges in quickly and accurately transferring millions of semiconductor light emitting devices due to high transfer error rates and lowered yield, particularly in self-assembly methods where directional control of LED chips and electrical contact characteristics are difficult, leading to reduced light efficiency and luminance.
Innovation Solution
A semiconductor light emitting device with a reflective contact layer including an AgAu alloy, which forms ohmic contact areas that improve light efficiency and assembly accuracy, and a manufacturing method involving metal layer deposition and heat treatment to create a thin, efficient reflective layer without increasing device thickness or process complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a self-assembly method using DEP force is used to transfer semiconductor light emitting devices, then transfer speed can be improved, but transfer error rate increases and transfer yield decreases
Solution Approach 1:
The patent applies local quality by creating asymmetric electrode structures with different widths at different locations. The first electrode has a first width and the second electrode has a second width different from the first, creating localized electric field variations that generate directional DEP forces. This local asymmetry in electrode geometry enables directional control of LED chips during self-assembly, resolving the contradiction between transfer speed and transfer yield by ensuring accurate positioning while maintaining rapid assembly.
2Productivity
If LED chip is assembled with tilted or reversed direction, then assembly speed may be maintained, but electrical disconnection defects occur in subsequent wiring process
Solution Approach 1:
The patent employs asymmetry by designing electrodes with different widths (first electrode with first width, second electrode with second width) and positioning them asymmetrically relative to the LED chip. This asymmetric electrode configuration creates an asymmetric electric field distribution that generates directional DEP forces, enabling the LED chip to self-align in the correct orientation during assembly. The asymmetric structure ensures that chips assemble in the proper direction without tilting or reversal, maintaining both assembly speed and electrical connection reliability.
3Use of energy by moving object
If reflective layer is added to improve light efficiency, then light efficiency increases, but device thickness increases and process difficulty increases
Solution Approach 1:
The patent merges multiple functions into the electrode structures by integrating both electrical contact and light reflection functions. The electrodes are designed with specific widths and materials that enable them to serve as both electrical contacts for the LED chip and as reflective layers for improving light extraction efficiency. This merging of functions eliminates the need for separate reflective layer deposition processes, maintaining thin device structure while improving light efficiency and reducing process difficulty.
Solution Approach 2:
The electrode structures in the patent exhibit multi-functionality by simultaneously performing electrical contact and optical reflection. The electrodes are configured with specific geometric parameters (different widths for first and second electrodes) that enable them to provide both electrical connectivity to the LED chip and reflective properties for enhancing light extraction. This universal design approach allows single components to fulfill multiple roles, improving light efficiency without increasing device complexity or process difficulty.
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
The solution enhances light efficiency, assembly accuracy, and reflectivity across RGB wavelength bands, improving electrical reliability and reducing process difficulty, while maintaining a thin device structure and preventing metal oxidation or peeling during self-assembly.
Implementation Method 1
a reflective contact layer disposed below the light emitting structure. Also, the reflective contact layer can include a first reflective layer including an AgAu alloy
Implementation Method 2
a self-assembly type transfer process using dielectrophoresis (DEP) has been attempted
Data Source
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AI summary
A semiconductor light emitting device including a light emitting structure and a reflective contact layer disposed below the light emitting structure. Further, the reflective contact layer includes a plurality of ohmic contact areas contacting a first conductivity-type semiconductor layer of the light emitting structure in which a first ohmic contact area has a different size than a second ohmic contact area included in the plurality of ohmic contact areas; and a first reflective layer comprising an AgAu alloy and covering the plurality of ohmic contact areas.