Micro LED Surface Roughness Layout for Adhesion and Light Extraction

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Solution Overview

Problem

Existing methods for transferring micro light-emitting elements to a substrate face challenges in achieving high transfer yield and light extraction efficiency due to low surface roughness, leading to reduced adhesion and increased total reflection of light.

Innovation Solution

The micro light-emitting elements are designed with a first conductivity type semiconductor layer having an uneven pattern and a transparent coating layer with a lower surface roughness, enhancing adhesion and reducing total reflection.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If the lower surface of the micro light-emitting element has a low surface roughness (several nm or less), then adhesion to the substrate is improved, but light extraction efficiency is reduced due to total reflection

Engineering Contradiction:

ImproveadhesionVSAvoidlight extraction efficiency

Core Design Contradiction:

StrengthVSLoss of energy

Solution Approach 1:

The patent applies different surface roughness characteristics to different surfaces of the micro light-emitting element. The lower surface (contacting the substrate) has low surface roughness (several nm or less) to maximize adhesion, while the upper surface (light emission surface) has high surface roughness (tens of nm to several μm) to minimize total reflection and improve light extraction efficiency. This local differentiation of surface properties resolves the contradiction between adhesion and light extraction.

Inventive Principle:

Principle #3Local quality

2Loss of energy

If the lower surface of the micro light-emitting element has a high surface roughness (tens of nm to several μm), then light extraction efficiency is improved, but adhesion to the substrate is reduced

Engineering Contradiction:

Improvelight extraction efficiencyVSAvoidadhesion

Core Design Contradiction:

Loss of energyVSStrength

Solution Approach 1:

Inventive Principle:

Principle #3Local quality

3Manufacturing precision

If multiple transfer processes are used for colored micro light-emitting elements, then color accuracy is improved, but manufacturing time and cost increase

Engineering Contradiction:

Improvecolor accuracyVSAvoidmanufacturing time

Core Design Contradiction:

Manufacturing precisionVSProductivity

Solution Approach 1:

The patent integrates the driving circuit board fabrication process with the micro light-emitting element transfer process. The transfer substrate is formed on the same substrate as the driving circuit board, allowing simultaneous formation of both components. This merging of processes eliminates separate transfer steps for different colored elements, improving manufacturing efficiency while maintaining color accuracy through precise transfer positioning.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The transfer substrate serves multiple functions: it acts as a support structure during fabrication, a positioning template for aligning micro light-emitting elements of different colors, and an integral part of the final driving circuit board assembly. This multi-functionality allows a single transfer process to handle multiple colored elements simultaneously, reducing manufacturing time and complexity.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 design improves both transfer yield and light extraction efficiency by increasing adhesion to the substrate while minimizing total reflection, resulting in improved manufacturing productivity and performance.

Implementation Method 1

due to adhesive force acting between the micro light-emitting element and the substrate

Methodology Applied

Scientific EffectAdhesion: Adhesive

Implementation Method 2

the light may not be output to the outside due to a total reflection on the lower surfaces of the micro light-emitting elements

Methodology Applied

Scientific EffectTotal internal reflection: Total Internal Reflection

Data Source

PatentUS20250344557A1Micro light-emitting element, micro light-emitting element array including the micro light-emitting element, and display device including the micro light-emitting element array

Publication Date: 2025.11.06 SAMSUNG ELECTRONICS CO LTD

AI summary

A micro light-emitting element includes a first conductivity type semiconductor layer including a lower surface on which an uneven pattern is formed, an active layer provided on the first conductivity type semiconductor layer, a second conductivity type semiconductor layer provided on the active layer, at least one electrode provided on the second conductivity type semiconductor layer, and a transparent coating layer including a first surface covering the lower surface of the first conductivity type semiconductor layer, and a second surface facing the first surface and having a second surface roughness that is less than a first surface roughness of the lower surface of the first conductivity type semiconductor layer.