AgAu Reflective Contact Layer for Micro-LED Transfer Yield
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The self-assembly method for micro-LED displays faces challenges in quickly and accurately transferring millions of semiconductor light emitting devices due to high transfer error rates and lowered yield, with issues in directional control of LED chips and decreased electrical contact characteristics, leading to reduced light efficiency and luminance, especially for red color emission.
Innovation Solution
A semiconductor light emitting device with a reflective contact layer including an AgAu alloy is used, which forms ohmic contact areas randomly distributed on the semiconductor layer, improving light efficiency and assembly accuracy without increasing process complexity or thickness, and ensuring high reflectivity across RGB wavelength bands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If self-assembly method is used to transfer millions of semiconductor light emitting devices, then transfer speed is improved, but transfer error rate increases and transfer yield decreases
Solution Approach 1:
The patent applies preliminary action by pre-forming凸起 structures on the semiconductor light emitting device and corresponding recesses on the substrate before the self-assembly transfer process. These pre-formed mechanical interlocking features ensure that when the devices self-assemble, they automatically align and lock into position, preventing transfer errors and improving yield while maintaining high transfer speed
Solution Approach 2:
The patent introduces凸起 structures as an intermediary mechanical feature that mediates between the semiconductor light emitting device and the substrate. These凸起 structures act as positioning and locking intermediaries that guide the self-assembly process, ensuring accurate placement and reducing transfer errors without compromising transfer speed
2Use of energy by moving object
If reflective layer is added to improve light efficiency, then light efficiency improves, but device thickness increases
Solution Approach 1:
The patent employs thin film technology by using an extremely thin reflective layer (5-50 nm) deposited on the semiconductor light emitting device. This thin film approach provides sufficient light reflection efficiency while minimizing the increase in device thickness, maintaining the overall compact structure of the display device
Solution Approach 2:
The patent applies parameter changes by optimizing the thickness and material composition of the reflective layer. By controlling the reflective layer thickness within 5-50 nm and selecting appropriate materials, the patent achieves high light efficiency while keeping the thickness increase minimal, thus resolving the contradiction between light efficiency and device thickness
3Reliability
If AgAu alloy is used for reflective contact layer, then reflectivity improves and oxidation resistance improves, but manufacturing complexity increases
Solution Approach 1:
The patent uses composite materials by combining Ag and Au in a specific alloy ratio (Ag:Au = 9:1 to 1:9) to create the reflective contact layer. This composite material approach provides both high reflectivity and excellent oxidation resistance, while the standardized alloy formulation simplifies the manufacturing process by using a proven material composition rather than requiring complex multi-layer structures
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 rate, and electrical reliability by preventing metal oxidation and peeling during self-assembly, while maintaining a thin structure and low process difficulty, achieving high reflectivity for each RGB color band.
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
Implementation Method 3
firstly moving the LED chip to the assembly hole area by magnetic force of the magnet
Data Source
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.