Thin-Film Transistor Circuit Substrate Top-Gate Structure

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Solution Overview

Problem

Inverted staggered type thin-film transistors using oxide semiconductors face challenges in reducing channel length and circuit area, and maintaining stability due to oxygen variation in the channel portion, leading to unstable transistor characteristics.

Innovation Solution

A method involving the formation of an oxide semiconductor thin film with distinct regions of varying resistance, covered by a silicon nitride interlayer insulation film with high dangling bonds of silicon, which stabilizes oxygen concentration and reduces resistance, allowing for a coplanar top-gate structure that enhances ON current and transistor capability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If an inverted staggered type TFT structure is used, then the fabrication process is simplified, but the channel length cannot be decreased and circuit area reduction is difficult

Engineering Contradiction:

Improvefabrication process simplicityVSAvoidchannel length

Core Design Contradiction:

Ease of manufactureVSLength of moving object

Solution Approach 1:

The patent inverts the conventional staggered structure by placing the gate electrode on top of the oxide semiconductor layer instead of below it. This top-gate configuration allows the channel length to be defined by the gate electrode width, enabling significant reduction in channel length and circuit area while maintaining fabrication simplicity

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent transitions from a planar bottom-gate structure to a vertical top-gate structure, changing the spatial arrangement dimension. This dimensional change allows the gate to control the channel more effectively and enables shorter channel lengths without compromising manufacturing ease

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Device complexity

If protection of the back channel side is not provided, then the manufacturing process is simplified, but oxygen concentration varies in the channel portion leading to unstable transistor characteristics

Engineering Contradiction:

Improveprocess complexityVSAvoidtransistor characteristic stability

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The patent forms the gate insulation film and gate electrode structure before subsequent processing steps that might affect oxygen concentration. This preliminary formation of the gate structure protects the channel region from oxygen variation during later manufacturing processes, ensuring stable transistor characteristics without adding complex protection steps

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The gate insulation film acts as an intermediary layer between the oxide semiconductor channel and the environment or subsequent processing steps. This intermediate layer prevents oxygen diffusion and contamination, stabilizing the channel region while maintaining process simplicity

Inventive Principle:

Principle #24Intermediary (Mediator)

3Area of stationary object

If the channel length is decreased to reduce circuit area, then the circuit density is improved, but the ON current capability is reduced

Engineering Contradiction:

Improvecircuit areaVSAvoidON current

Core Design Contradiction:

Area of stationary objectVSPower

Solution Approach 1:

The patent changes the electrical parameters of the oxide semiconductor by controlling oxygen concentration and stoichiometry in the channel region. By optimizing these material parameters, the semiconductor achieves higher carrier mobility and conductivity, compensating for the reduced channel length and maintaining high ON current capability in compact devices

Inventive Principle:

Principle #35Parameter changes

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 stable transistor characteristics, reduces manufacturing complexity, and lowers costs by eliminating the need for additional resistance-decreasing processes, while allowing for smaller channel lengths and improved circuit density.

Implementation Method 1

forming an interlayer insulation film of silicon nitride including dangling bonds of silicon... the interlayer insulation film stabilizes oxygen concentration

Methodology Applied

Scientific EffectOxygen absorption: Absorption (physical)

Implementation Method 2

the interlayer insulation film... reduces resistance

Methodology Applied

Scientific EffectResistivity change through oxygen extraction:

Data Source

PatentUS9123588B2Thin-film transistor circuit substrate and method of manufacturing the same

Publication Date: 2015.09.01 MAGNOLIA WHITE CORP

AI summary

According to one embodiment, a method of manufacturing a thin-film transistor circuit substrate including forming an oxide semiconductor thin film above an insulative substrate, forming a gate insulation film and a gate electrode which are stacked on a first region of the oxide semiconductor thin film, and exposing from the gate insulation film a second region and a third region of the oxide semiconductor thin film, the second region and the third region being located on both sides of the first region of the oxide semiconductor thin film, forming an interlayer insulation film of silicon nitride including dangling bonds of silicon, the interlayer insulation film covering the second region and the third region of the oxide semiconductor thin film, the gate insulation film and the gate electrode, and forming a source electrode and a drain electrode.