Oxide Semiconductor TFT Laminated Gate Insulation

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Solution Overview

Problem

Oxide semiconductor-based thin film transistors (TFTs) face issues with oxygen desorption and hydrogen exposure, leading to lattice defects, reduced resistance, and increased leakage current due to the lack of effective barrier layers during manufacturing, particularly with existing gate insulation and passivation films.

Innovation Solution

A laminated film configuration is introduced, comprising a first layer of aluminum oxide and a second layer of silicon-based insulation material for the gate insulation film and channel protection, and a passivation film made of oxides, nitrides, or oxynitrides containing aluminum, titanium, or tantalum to prevent oxygen and hydrogen exposure, thereby stabilizing the oxide semiconductor layer.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a thick gate insulation layer of aluminum oxide is used to suppress oxygen desorption, then the protection capability is improved, but the film formation time becomes excessively long

Engineering Contradiction:

Improveprotection capabilityVSAvoidfilm formation time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The gate insulation layer is divided into multiple layers: a first gate insulation layer (aluminum oxide) in direct contact with the oxide semiconductor layer to suppress oxygen desorption, and a second gate insulation layer (silicon-based) formed on top to provide additional protection and enable faster film formation. This segmentation allows each layer to have optimized thickness and material properties, achieving both protection capability and reduced formation time.

Inventive Principle:

Principle #1Segmentation

2Reliability

If conventional passivation films are used to protect against hydrogen exposure, then some protection is provided, but the protection capability is insufficient

Engineering Contradiction:

Improveprotection capabilityVSAvoidhydrogen exposure

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The passivation film is constructed as a laminated structure combining aluminum oxide and silicon-based insulation materials. This composite structure provides superior barrier properties against hydrogen exposure compared to conventional single-material passivation films, while also offering complementary protection against oxygen desorption and moisture ingress.

Inventive Principle:

Principle #40Composite materials

3Ease of manufacture

If the oxide semiconductor layer is exposed to air during manufacturing, then the manufacturing process is simplified, but oxygen desorption and hydrogen reduction occur causing lattice defects

Engineering Contradiction:

Improvemanufacturing simplicityVSAvoidlattice defect level

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The gate insulation layer and passivation film are formed to enclose the oxide semiconductor layer before subsequent manufacturing steps that involve exposure to air or hydrogen-containing environments. This preliminary protective action prevents oxygen desorption and hydrogen-induced lattice defects from occurring during the manufacturing process, maintaining manufacturing simplicity while ensuring high precision.

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 configuration effectively suppresses oxygen desorption and hydrogen-induced reduction, stabilizing the electrical characteristics of the TFT, reducing leakage current, and shortening film formation time compared to single-layer aluminum oxide configurations.

Implementation Method 1

a first layer made of aluminum oxide... suppresses desorption of oxygen and others from an oxide semiconductor layer

Methodology Applied

Scientific EffectPhysical barrier:

Implementation Method 2

a second later made of an insulation material including silicon (Si)... shortening film formation time

Methodology Applied

Scientific EffectFilm deposition: Deposition (physical)

Implementation Method 3

the hydrogen in the air reduces the oxygen in the oxide semiconductor... passivation film having the enhanced capabilities of being able to serve as a barrier against the oxygen and hydrogen

Methodology Applied

Scientific EffectDiffusion barrier: Diffusion Barrier

Data Source

PatentUS8742418B2Thin film transistor and display device

Publication Date: 2014.06.03 MAGNOLIA BLUE CORP

AI summary

A thin film transistor comprising: a substrate; a gate electrode on the substrate; a gate insulation film on the gate electrode; an oxide semiconductor layer on the gate insulation film; a channel protection film on the oxide semiconductor layer; source and drain electrodes on the channel protection film; and a passivation film on the source and drain electrodes, wherein, (a) each of the gate insulation film, and passivation film comprises a laminated structure and includes a first layer made of aluminum oxide and a second layer made of an insulation material including silicon, and (b) the passivation film covers edges of the oxide semiconductor layer. The transistor is capable of suppressing desorption of oxygen and from the oxide semiconductor layer and reducing the time for film formation thereof.