Composite Reflective Structure With Stress Buffer for LED Chips

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Solution Overview

Problem

Conventional reflective structures for semiconductor devices, such as distributed Bragg reflectors, experience high stress between layers due to high-energy deposition processes, leading to film peeling, breaking, and reduced light extraction efficiency.

Innovation Solution

A composite reflective structure is introduced, featuring a dielectric multilayer element with a stress buffer layer interposed between layers of different refractive indices, reducing stress and enhancing light reflection efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Illumination intensity

If a conventional distributed Bragg reflector is formed by alternate stacking of high and low refractive index films using high-energy plating process, then light reflection efficiency is improved, but high stress is generated between films causing film peeling, film breaking and roughness

Engineering Contradiction:

Improvelight reflection efficiencyVSAvoidfilm integrity

Core Design Contradiction:

Illumination intensityVSStrength

Solution Approach 1:

A stress buffer layer with intermediate refractive index (1.7-2.2) is introduced between the high refractive index dielectric layer and low refractive index dielectric layer. This intermediary layer acts as a stress mediator that reduces the stress generated during high-energy plating deposition, preventing film peeling and breaking while maintaining the optical reflection performance of the distributed Bragg reflector structure.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The reflector structure uses a composite multilayer design combining dielectric layers of different refractive indices with an intermediate stress buffer layer. This composite structure integrates both optical functionality (high reflection efficiency through refractive index contrast) and mechanical stability (stress reduction through the buffer layer), solving the contradiction between light reflection efficiency and film integrity.

Inventive Principle:

Principle #40Composite materials

2Reliability

If high-energy plating process is used to form dielectric films, then film density and optical properties are improved, but high stress is generated resulting in film peeling and breaking

Engineering Contradiction:

Improveoptical property stabilityVSAvoidfilm stress

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The stress buffer layer serves as a protective intermediary that absorbs and distributes the stress generated during high-energy plating deposition. This allows the high-energy process to continue (maintaining film density and optical properties) while the buffer layer prevents the harmful stress effects of peeling and breaking.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The stress buffer layer is pre-positioned between the high and low refractive index dielectric layers before the high-energy plating process generates excessive stress. This beforehand cushioning structure is designed to anticipate and absorb the stress that will be generated, preventing film failure while allowing the high-energy deposition to proceed.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

3Illumination intensity

If alternate stacking of high and low refractive index films is performed, then light extraction efficiency is improved, but roughness between films increases due to stress

Engineering Contradiction:

Improvelight extraction efficiencyVSAvoidfilm surface smoothness

Core Design Contradiction:

Illumination intensityVSManufacturing precision

Solution Approach 1:

The stress buffer layer acts as a smoothing intermediary between the high and low refractive index dielectric layers. By reducing the interfacial stress, it prevents stress-induced roughness formation, thereby maintaining smooth film interfaces that are necessary for high light extraction efficiency in the distributed Bragg reflector structure.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 composite structure effectively reduces internal stress, preventing film peeling and breaking, and maintains high light reflection efficiency across various incident angles, as demonstrated by improved spectral reflectance and reduced die chipping during laser cutting.

Implementation Method 1

a stress buffer layer interposed therebetween

Methodology Applied

Scientific EffectStress buffer: Stress Relaxation

Implementation Method 2

a first dielectric layer having a first refractive index, a second dielectric layer having a second refractive index

Methodology Applied

Scientific EffectLight reflection: Reflection

Implementation Method 3

a conventional reflective structure adapted for a semiconductor device (such as light-emitting diode device) is a distributed Bragg reflector (DBR)

Methodology Applied

Scientific EffectDistributed Bragg reflection: Bragg Diffraction

Data Source

PatentUS12015104B2Composite reflective structure and light-emitting diode chip and light-emitting diode device including the same

Publication Date: 2024.06.18 XIAMEN SANAN OPTOELECTRONICS CO LTD

AI summary

A composite reflective structure includes at least one dielectric multilayer element which includes a first dielectric layer having a first refractive index, a second dielectric layer having a second refractive index, and a stress buffer layer interposed therebetween. The first refractive index is greater than the second refractive index. Also disclosed herein is a light-emitting diode chip including the abovementioned composite reflective structure and a light-emitting diode device including the light-emitting diode chip.