Micro-LED Module Laser Lift-Off Buffer Layer Protection
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Solution Overview
Problem
The use of a sapphire substrate in micro-LED modules leads to light extraction efficiency deterioration and risks laser-induced damage to the epilayer and circuit between LED cells during the laser lift-off process for substrate removal.
Innovation Solution
A method involving the formation of a buffer layer between the micro-LED and the submount substrate, which absorbs laser energy and protects the micro-LED and submount substrate from damage, ensuring stable bonding and efficient light extraction by removing the sapphire substrate using a laser lift-off process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the sapphire substrate is removed by laser lift-off process, then light extraction efficiency is improved, but laser-induced damage to epilayer and circuit occurs
Solution Approach 1:
A buffer layer is introduced as an intermediary substance between the sapphire substrate and the micro-LED chip. This buffer layer absorbs the laser energy during the lift-off process, protecting the epilayer and circuit from laser-induced damage while allowing the sapphire substrate to be successfully removed for improved light extraction efficiency
Solution Approach 2:
The harmful laser energy that could damage the epilayer and circuit is converted into a beneficial protective mechanism. The buffer layer absorbs this harmful laser energy, transforming it into a protective function that enables safe substrate removal while maintaining the integrity of sensitive components
2Stability of the object's composition
If the sapphire substrate is kept for structural support, then mechanical stability is improved, but light extraction efficiency deteriorates
Solution Approach 1:
The substrate structure is segmented into two functional parts: the sapphire substrate that provides mechanical stability and support, and the buffer layer that enables light extraction by being positioned between the sapphire substrate and the micro-LED chip. This segmentation allows each component to fulfill its specific function without compromising the other
Solution Approach 2:
The buffer layer serves as an intermediary that optically decouples the micro-LED chip from the sapphire substrate. This intermediary structure allows the sapphire substrate to maintain mechanical stability while the buffer layer facilitates improved light extraction efficiency
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 method enhances the bonding strength between the micro-LED and submount substrate, prevents laser-induced damage, and maintains high light extraction efficiency by effectively removing the sapphire substrate while ensuring the micro-LED module's stability and image quality.
Implementation Method 1
forming a buffer layer between the micro-LED and the submount substrate, which absorbs laser energy and protects the micro-LED and submount substrate from damage
Implementation Method 2
irradiating a laser between the sapphire substrate and the semiconductor layer to separate the semiconductor layer from the sapphire substrate
Data Source
AI summary
Disclosed is a method for fabricating a high-efficiency micro-LED module. The method includes: preparing a micro-LED in which an epilayer is grown on a sapphire substrate, a plurality of LED cells are formed on the epilayer, a plurality of individual electrode pads are disposed such that one individual electrode pad is assigned to each LED cell, and a common electrode pad is formed on an area surrounding the plurality of LED cells; preparing a submount substrate including a plurality of individual electrodes corresponding to the individual electrode pads and a common electrode corresponding to the common electrode pad; mounting the micro-LED on the submount substrate such that the plurality of individual electrodes are connected to the plurality of individual electrode pads and the common electrode pad is connected to the common electrode through a plurality of bonding connection members; forming a buffer layer between the micro-LED and the submount substrate; and irradiating a laser around the boundary between the sapphire substrate and the epilayer to separate the sapphire substrate from the epilayer, wherein the buffer layer absorbs energy produced by the laser at least between the neighboring LED cells to protect the epilayer or the surmount substrate from damage.