Micro-LED Trench Filling for Optical Crosstalk Reduction

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Solution Overview

Problem

Micro-LED arrays face issues with poor display contrast due to strong optical crosstalk between adjacent pixels, caused by light scattering from sloped mesas and unreliable isolation layers leading to electric crosstalk and reliability problems.

Innovation Solution

A non-transparent or substantially non-transparent material is used to fill the trenches between raised mesa areas in micro-LED arrays, blocking unwanted light and providing optical and electrical isolation, thereby reducing crosstalk and improving contrast.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If transparent polyimide is used to fill gaps between LEDs, then light extraction efficiency is improved due to increased refractive index, but optical crosstalk between adjacent pixels increases resulting in poor display contrast

Engineering Contradiction:

Improvelight extraction efficiencyVSAvoidoptical crosstalk

Core Design Contradiction:

Use of energy by moving objectVSObject-affected harmful factors

Solution Approach 1:

The patent applies different optical properties to different regions: transparent polyimide is used in regions where light extraction is needed (on the LEDs themselves), while opaque or light-absorbing material is used in the trench regions between LEDs to prevent crosstalk. This spatial differentiation of material properties resolves the contradiction between improving light extraction and preventing optical interference.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The invention uses a composite structure combining transparent polyimide material with opaque or light-absorbing material in the trenches. This composite approach allows simultaneous achievement of high light extraction efficiency from individual LEDs while blocking optical crosstalk between adjacent pixels, thereby improving display contrast.

Inventive Principle:

Principle #40Composite materials

2Adaptability or versatility

If dry etch is used to form isolated LED mesa columns, then matrix-addressable LED array structure is achieved, but light scattering from sloped mesas and sharp edges increases reducing display contrast

Engineering Contradiction:

Improvematrix-addressable structureVSAvoidlight scattering

Core Design Contradiction:

Adaptability or versatilityVSObject-affected harmful factors

Solution Approach 1:

The patent extracts or removes the harmful light scattering effect by filling the trenches between mesas with opaque or light-absorbing material. This material blocks and absorbs the scattered light from sloped mesas and sharp edges, preventing it from reaching adjacent pixels and degrading display contrast.

Inventive Principle:

Principle #2Taking out (Extraction)

3Device complexity

If thin dielectric layer is used for isolation between p-contacts and n-contacts, then manufacturing complexity is reduced, but reliability decreases due to adhesion issues and electrical crosstalk

Engineering Contradiction:

Improveisolation layer structureVSAvoidelectrical isolation reliability

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The patent employs a composite isolation structure combining thin dielectric layer with opaque or light-absorbing material in the trenches. This combination provides both electrical isolation (from the dielectric) and optical isolation (from the opaque material), thereby improving reliability without significantly increasing manufacturing complexity.

Inventive Principle:

Principle #40Composite materials

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 solution effectively reduces optical crosstalk and enhances display contrast, improves device reliability by eliminating electric crosstalk, and allows for conformal metal deposition, reducing light scattering and thermal issues.

Implementation Method 1

a non-transparent or substantially non-transparent material capable of blocking light emitted from within the micro-LED array

Methodology Applied

Scientific EffectLight blocking: Absorption (EM radiation)

Implementation Method 2

located between the at least two raised mesa areas there is a trench

Methodology Applied

Scientific EffectPhysical isolation: Physical Containment

Data Source

PatentUS10490715B2Display contrast

Publication Date: 2019.11.26 META PLATFORMS TECHNOLOGIES LLC

AI summary

Display devices with improved display contrast and methods of manufacturing the display devices. Some embodiments include a method of manufacturing a light emitting diode (LED) array. The method includes forming a first mesa area of a first LED and a second mesa area of a second LED, where a trench is defined between the first and second mesa areas. At least a portion of the trench is filled with a non-transparent or substantially non-transparent polymeric material that absorbs light emitted from the first and second LEDs.