TFT Electrode Ionization Tendency Matching for Corrosion Resistance

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Solution Overview

Problem

In display devices using thin film transistors (TFTs) with oxide semiconductors, the difference in ionization tendency between low-resistance metal wiring layers and transparent conductive oxide electrodes leads to electrolytic corrosion, causing unstable electrical characteristics.

Innovation Solution

A display device design where a thin film transistor includes a control electrode, a semiconductor layer, a first electrode made of a light transmissive material, and a second electrode with a metal film having lower resistance, where the ionization tendency difference between the metal film and the wiring layer is minimized, reducing electrolytic corrosion by ensuring the second electrode is electrically connected to both the semiconductor layer and the wiring layer.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a low-resistance metal wiring layer and a transparent conductive oxide source/drain electrode are used with different ionization tendencies, then electrical connectivity is achieved, but electrolytic corrosion occurs causing unstable resistance

Engineering Contradiction:

Improveelectrical characteristic stabilityVSAvoidelectrolytic corrosion

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

An intermediary layer made of the same material as the wiring layer is introduced between the transparent conductive oxide electrode and the wiring layer. This intermediary layer acts as a mediator that prevents direct contact between materials with different ionization tendencies, thereby eliminating the electrolytic corrosion reaction while maintaining electrical connectivity.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The invention converts the harmful effect of ionization tendency difference into a beneficial design feature by deliberately using the same material for both the wiring layer and the intermediary layer. This ensures that when these two layers are in contact, no electrolytic corrosion occurs, transforming the potential harm into a reliable electrical connection.

Inventive Principle:

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

2Illumination intensity

If transparent conductive oxide film is used as electrode, then light transmissivity is achieved, but resistance becomes high making it unsuitable for main wiring

Engineering Contradiction:

Improvelight transmissivityVSAvoidelectrical resistance

Core Design Contradiction:

Illumination intensityVSReliability

Solution Approach 1:

The invention uses a composite structure combining transparent conductive oxide material and low-resistance metal material in the electrode/wiring system. The transparent conductive oxide provides light transmissivity and interface compatibility, while the low-resistance metal provides excellent electrical conductivity, achieving both optical and electrical performance requirements.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The electrode and wiring structures are segmented into different functional layers: transparent conductive oxide layers where light transmissivity is critical, and low-resistance metal layers where electrical conductivity is critical. This segmentation allows each material to perform its optimal function without compromise.

Inventive Principle:

Principle #1Segmentation

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 configuration stabilizes electrical characteristics by reducing electrolytic corrosion between the second electrode and the wiring layer, ensuring consistent performance in display devices.

Implementation Method 1

the difference in ionization tendency between a low-resistance metal and a transparent conductive oxide is great, so when an electrode and a wiring layer which are electrically connected to each other are immersed in chemical solution such as a resist stripping solution, electrolytic corrosion occurs

Methodology Applied

Scientific EffectElectrolytic corrosion: Electrolysis

Data Source

PatentUS9219084B2Display device including a thin film transistor having wiring and electrodes with different ionization tendencies

Publication Date: 2015.12.22 MAGNOLIA BLUE CORP

AI summary

A display device includes a thin film transistor and a wiring layer. The thin film transistor including a control electrode, a semiconductor layer facing the control electrode, a first electrode electrically connected to the semiconductor layer, and a second electrode including a metal film having resistance lower than that of the light transmissive material. The second electrode is electrically connected to each of the semiconductor layer and the wiring layer. A difference in ionization tendency between a material configuring the metal film and a conductive material configuring a part or whole of the wiring layer is smaller than a difference in ionization tendency between the light transmissive material and the conductive material.