Inorganic LED Transfer to TFT Backplane

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Solution Overview

Problem

Current OLED displays face challenges with encapsulation, lifetime, yield, color efficiency, and drive electronics, and lack the resolution needed for next-generation displays, while inorganic LEDs offer superior performance but require high deposition temperatures incompatible with flexible substrates.

Innovation Solution

A method involving stress-induced spalling and mechanical bonding of inorganic LED layers onto an active matrix TFT backplane, allowing for the integration of inorganic LEDs onto flexible or rigid substrates without the need for low-temperature deposition, using a stress-induced spalling technique to transfer and bond inorganic LED layers to a TFT backplane array.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If inorganic LED material is grown on a base substrate using conventional methods, then high efficiency and long lifetime are achieved, but high deposition temperature is required which is incompatible with flexible substrates

Engineering Contradiction:

ImproveLED lifetime and efficiencyVSAvoiddeposition temperature

Core Design Contradiction:

ReliabilityVSTemperature

Solution Approach 1:

The inorganic LED structure is segmented into two parts: the LED active layers grown on a temporary base substrate, and the TFT backplane. The LED layers are then transferred to the TFT backplane, allowing the LED material to be grown at high temperatures on the base substrate while the flexible TFT backplane is processed separately at low temperatures.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

A stress-induced spalling technique is used as an intermediary method to transfer the LED layers from the base substrate to the TFT backplane. This spalling process enables separation of the LED layers at the interface between the base substrate and LED material, allowing transfer without direct high-temperature processing on the flexible substrate.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Adaptability or versatility

If OLED displays are used to achieve flexibility and low cost, then lighter weight and flexible substrates are enabled, but encapsulation, lifetime, and color efficiency problems persist

Engineering Contradiction:

Improveflexibility and costVSAvoidencapsulation and lifetime

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The invention creates a hybrid display structure combining the advantages of inorganic LEDs (superior lifetime, efficiency, and color performance) with the flexibility and low-cost processing of TFT backplanes. The composite structure integrates inorganic LED layers transferred onto a flexible TFT substrate, achieving both reliability and adaptability.

Inventive Principle:

Principle #40Composite materials

3Manufacturing precision

If active matrix addressing scheme is used to achieve high information content formats, then resolution needed for next generation displays is supported, but integration of high-performance inorganic LEDs with TFT backplane is challenging

Engineering Contradiction:

Improvedisplay resolutionVSAvoidintegration complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The display is segmented into independent TFT backplane and LED layer components that are processed separately and then transferred. This allows the LED layers to be optimized for high-resolution performance while the TFT backplane is optimized for active matrix addressing, reducing integration complexity.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The LED layers are prepared and grown on the base substrate in advance, allowing optimization of LED material quality and structure for high-resolution displays before transfer. The TFT backplane is also prepared separately with the active matrix addressing scheme already in place, so both components are ready for integration without complex simultaneous processing.

Inventive Principle:

Principle #10Preliminary action

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 approach enables the creation of high-resolution active matrix inorganic LED displays with improved efficiency and flexibility, overcoming the limitations of OLEDs and achieving performance comparable to inorganic LEDs without the high deposition temperature constraints.

Implementation Method 1

separating the one or more layers of the inorganic LED material from the base substrate by a stress-induced spalling technique

Methodology Applied

Scientific EffectStress-induced spalling: Fracture Mechanics

Implementation Method 2

bonding the separated one or more layers of inorganic LED material to an active matrix, thin film transistor (TFT) backplane array

Methodology Applied

Scientific EffectMechanical bonding: Welding

Data Source

PatentUS8912020B2Integrating active matrix inorganic light emitting diodes for display devices

Publication Date: 2014.12.16 GLOBALFOUNDRIES US INC

AI summary

A method of forming an active matrix, light emitting diode (LED) array includes removing, from a base substrate, a layer of inorganic LED material originally grown thereupon; and bonding the removed layer of inorganic LED material to an active matrix, thin film transistor (TFT) backplane array.