Micro-LED Structure With Obtuse Sidewall Angle for Defect-Free Assembly
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Large-area micro-LED displays face challenges in quickly and accurately transferring millions of micro-LEDs due to defects such as chain defects, lump defects, non-assembly defects, color mixing defects, and contact defects during the self-assembly process, which affect yield and optical/electrical properties.
Innovation Solution
The semiconductor light emitting device features a light emitting layer with a passivation layer on the upper and side surfaces, a protective layer on the lower and side surfaces, and electrodes positioned to optimize the inner angles for improved assembly and connection, including conductive layers on the side surfaces to enhance the assembly force and prevent defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the self-assembly method is used to transfer micro-LEDs, then the transfer speed and scalability are improved, but assembly defects such as chain defects, lump defects, and non-assembly defects occur
Solution Approach 1:
The patent applies preliminary action by pre-forming the light emitting layer with a specific shape (obtuse angle between side surface and lower surface) before the self-assembly process. This pre-shaping ensures that during magnet movement and DEP force assembly, the micro-LEDs naturally align with assembly holes and resist chain/lump defects, thereby improving assembly reliability while maintaining high transfer speed
Solution Approach 2:
The patent changes the geometric parameter of the light emitting layer from a conventional shape to one with an obtuse angle (greater than 90 degrees) between the side surface and lower surface. This parameter change optimizes the interaction with magnetic fields and DEP forces during self-assembly, preventing assembly defects while enabling high-speed transfer of millions of micro-LEDs
2Device complexity
If the inner angle between side surface and lower surface of light emitting layer is acute, then the device structure is simpler, but assembly force is insufficient causing non-assembly defects and separation
Solution Approach 1:
The patent changes the critical geometric parameter of the light emitting layer from an acute angle to an obtuse angle (greater than 90 degrees) between the side surface and lower surface. This parameter change increases the assembly force by optimizing the interaction with DEP forces and magnetic fields, preventing non-assembly defects and separation while maintaining reasonable structural complexity
3Reliability
If metal is provided on the lower side of semiconductor light emitting device, then electrode function is achieved, but chain defects and lump defects occur due to exposed metal
Solution Approach 1:
The patent applies local quality by providing the protective layer selectively on specific regions where metal electrodes are exposed. This localized protection prevents chain defects and lump defects only in the necessary areas while maintaining electrode functionality, rather than covering the entire device structure
Solution Approach 2:
The patent introduces a protective layer as an intermediary substance between the exposed metal electrode and the external environment during self-assembly. This intermediary layer prevents harmful interactions that cause chain and lump defects while allowing the metal electrode to maintain its electrical function
4Device complexity
If epi layer is exposed to the outside, then device structure is simpler, but epi layer is damaged due to impact during magnet movement and DEP force assembly
Solution Approach 1:
The patent applies preliminary action by pre-forming the light emitting layer with an obtuse angle geometry before the self-assembly process. This pre-shaping creates a more robust structure that resists damage during magnet movement and DEP force assembly, preventing epi layer damage while maintaining reasonable structural complexity
Solution Approach 2:
The patent provides beforehand cushioning by creating a geometric configuration (obtuse angle) that inherently absorbs and distributes mechanical stresses during self-assembly. This pre-engineered stress distribution prevents impact damage to the epi layer during magnet movement and DEP force application
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 configuration enhances the assembly rate, prevents defects, and improves the electrical and optical properties by ensuring proper assembly and connection of micro-LEDs, thereby increasing the yield and reliability of large-area micro-LED displays.
Implementation Method 1
a first process of moving numerous semiconductor light emitting devices dispersed in a fluid onto a backplane substrate using a magnet
Implementation Method 2
a second process of assembling the numerous semiconductor light emitting devices moved onto the backplane substrate into corresponding assembly holes using dielectrophoresis force (hereinafter referred to as DEP force)
Data Source
Figure 1(a)~1(b)
Figure 2(a)~2(b)
Figure 3~4
AI summary
A semiconductor light emitting device (150A) can comprise a light emitting layer (152), a passivation layer (157) on an upper surface (150a2) and a side surface (150a3) of the light emitting layer, a protective layer (158) on a lower surface (150a1) and the side surface of the light emitting layer (152), a first electrode (154) between the light emitting layer and the protective layer (158), and a second electrode (155) between the light emitting layer and the passivation layer. An inner angle (Θ1) between the side surface (150a3) and the lower surface (150a1) of the light emitting layer has an obtuse angle. Figure 13