Oxide Semiconductor Thin Film Transistor Oxygen Barrier Metal Layer

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Solution Overview

Problem

Oxygen desorption from oxide semiconductor films in thin film transistors leads to deterioration in current-voltage characteristics, affecting the reliability of the devices over time.

Innovation Solution

A thin film transistor design where the first metal layer in contact with the oxide semiconductor film is made of a metal with ionization energy equal to or higher than molybdenum, or a nitride/silicon nitride with oxygen barrier properties, preventing oxygen desorption and carrier generation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a metal layer with low ionization energy (susceptible to oxidation) is used in contact with the oxide semiconductor film, then oxygen is easily taken by the metal layer with oxidation, but this causes oxygen desorption from the oxide semiconductor film and carrier generation, deteriorating electric characteristics

Engineering Contradiction:

Improveelectric characteristics stabilityVSAvoidoxygen loss from oxide semiconductor film

Core Design Contradiction:

ReliabilityVSLoss of substance

Solution Approach 1:

The patent changes the ionization energy parameter of the metal layer by selecting metals with ionization energy equal to or higher than molybdenum (such as aluminum, titanium, tungsten, platinum, or their alloys). This parameter change prevents oxidation-induced oxygen desorption from the oxide semiconductor film, thereby maintaining stable electric characteristics and improving device reliability

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent employs composite material structures where a metal layer with appropriate ionization energy is combined with the oxide semiconductor film. This composite structure ensures that the metal layer does not extract oxygen from the semiconductor, preventing carrier generation and maintaining stable electrical properties over time

Inventive Principle:

Principle #40Composite materials

2Reliability

If the metal layer in contact with oxide semiconductor film is made of a metal susceptible to oxidation, then oxygen is taken by the metal layer, but this leads to oxygen desorption and carrier generation in the oxide semiconductor film

Engineering Contradiction:

Improvecurrent-voltage characteristic stabilityVSAvoidcarrier generation due to oxygen loss

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The patent modifies the chemical parameter (ionization energy) of the contact metal layer to be equal to or higher than molybdenum. This prevents the metal from oxidizing and extracting oxygen from the oxide semiconductor film, thereby eliminating the harmful effect of carrier generation and maintaining stable current-voltage characteristics

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent converts the potential harm of metal oxidation into a benefit by selecting metals with high ionization energy that resist oxidation. This prevents oxygen desorption and carrier generation, transforming what would be a harmful oxidation process into a protective barrier that maintains device performance

Inventive Principle:

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

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 suppresses carrier generation due to oxygen loss, thereby improving the reliability and maintaining stable electric characteristics over time.

Implementation Method 1

The first metal layer is made of a metal having ionization energy equal to or higher than molybdenum (Mo)

Methodology Applied

Scientific EffectIonization energy:

Implementation Method 2

a metal having oxygen barrier property, or a nitride or a silicon nitride of the metal having oxygen barrier property

Methodology Applied

Scientific EffectOxygen barrier property: Diffusion Barrier

Data Source

PatentUS8319226B2Thin film transistor and display device

Publication Date: 2012.11.27 MAGNOLIA BLUE CORP

AI summary

The present invention provides a thin film transistor realizing improved reliability by suppressing deterioration in electric characteristics. The thin film transistor includes an oxide semiconductor film forming a channel; a gate electrode disposed on one side of the oxide semiconductor film via a gate insulating film; and a pair of electrodes formed as a source electrode and a drain electrode in contact with the oxide semiconductor film and obtained by stacking at least first and second metal layers in order from the side of the oxide semiconductor film The first metal layer is made of a metal having ionization energy equal to or higher than molybdenum (Mo), a metal having oxygen barrier property, or a nitride or a silicon nitride of the metal having oxygen barrier property.