LED Substrate Reuse via Sacrificial Layer Laser Lift-Off

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Solution Overview

Problem

Existing light emitting diodes (LEDs) face challenges in improving reliability and performance due to limitations in light extraction structures, current spreading, and substrate separation processes, which can lead to damage during laser lift-off and affect the reuse of substrates.

Innovation Solution

A light emitting diode structure is developed with a nitride semiconductor layer, a current spreading layer, and a sacrificial layer, where the spreading layer has higher thermal conductivity and band gap energy than the substrate, allowing for uniform energy distribution and minimizing damage during laser lift-off, enabling substrate separation and reuse.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If laser lift-off technique is used to separate substrate, then substrate separation is achieved, but substrate damage occurs and substrate reuse becomes difficult

Engineering Contradiction:

Improvesubstrate separation qualityVSAvoidsubstrate integrity and reusability

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

The invention introduces a sacrificial layer as a separate functional component between the substrate and the light-emitting structure. This segmentation allows the substrate to be separated cleanly from the light-emitting structure through laser lift-off, while the sacrificial layer absorbs the laser energy and prevents damage to the substrate, enabling substrate reuse.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The sacrificial layer acts as an intermediary between the substrate and the light-emitting structure. During laser lift-off, it mediates the separation process by absorbing laser energy and facilitating clean detachment, while protecting the substrate from direct laser exposure and thermal damage, thus maintaining substrate integrity for potential reuse.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Ease of manufacture

If conventional LED structure is used, then manufacturing is simpler, but light extraction efficiency and current spreading are insufficient

Engineering Contradiction:

Improvemanufacturing simplicityVSAvoidlight extraction efficiency and current spreading performance

Core Design Contradiction:

Ease of manufactureVSProductivity

Solution Approach 1:

The invention employs a composite structure combining multiple semiconductor layers with different properties: a first conductive type semiconductor layer, a second conductive type semiconductor layer, and a light-emitting layer in between. This composite structure enhances both light extraction efficiency and current spreading performance while maintaining compatibility with conventional manufacturing processes.

Inventive Principle:

Principle #40Composite materials

3Loss of substance

If substrate is reused after laser lift-off, then manufacturing cost decreases, but substrate damage from laser exposure increases

Engineering Contradiction:

Improvesubstrate material utilizationVSAvoidlaser-induced substrate damage

Core Design Contradiction:

Loss of substanceVSObject-affected harmful factors

Solution Approach 1:

The invention converts the harmful laser energy that would damage the substrate into a beneficial separation mechanism. The sacrificial layer is specifically designed to absorb the laser energy and convert it into controlled thermal effects that facilitate clean separation, while the substrate remains protected from direct laser exposure, enabling its reuse.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The sacrificial layer functions as a disposable component that is intentionally designed to be consumed during the separation process. It serves its purpose of protecting the substrate and enabling separation, then is removed or remains as a thin residue, while the expensive substrate is preserved for reuse, improving overall material utilization.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

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 proposed solution enhances the reliability of the LED manufacturing process by reducing substrate damage and improving the separation process, allowing for the reuse of substrates and enhancing the overall performance and efficiency of the light emitting diode.

Implementation Method 1

Band gap energy of the spreading layer is greater than energy of the laser beam

Methodology Applied

Scientific EffectBand gap energy absorption: Absorption (EM radiation)

Implementation Method 2

thermal conductivity of the spreading layer is greater than thermal conductivity of the substrate

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Implementation Method 3

separating the substrate by irradiating a laser beam into a lower portion of the substrate to decompose the sacrificial layer

Methodology Applied

Scientific EffectLaser decomposition: Laser Ablation

Data Source

PatentEP2363895B1Light emitting device, method of manufacturing the same, light emitting device package

Publication Date: 2019.09.25 LG INNOTEK CO LTD

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AI summary

Disclosed is a method of manufacturing a light emitting device. The light emitting device includes a nitride semiconductor layer (115), an electrode on the nitride semiconductor layer, a light emitting structure (145) including a first conductive type semiconductor layer (130), an active layer (140), and a second conductive type semiconductor layer (150) under the nitride semiconductor layer, and a conductive layer (160) under the light emitting structure. The nitride semiconductor layer has band gap energy lower than band gap energy of the first conductive type semiconductor layer.