Oxide Semiconductor TFT Metal Extraction Prevention
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Solution Overview
Problem
Oxide semiconductor thin-film transistors (TFTs) face issues with reactions between the oxide semiconductor and electrode materials, leading to decreased charge mobility, electrical instability, and reliability due to metal extraction and oxidation, which affects the composition of the channel layer and increases resistance.
Innovation Solution
Incorporating an added element with a higher oxide formation free energy into the oxide semiconductor pattern, specifically at the surface contacting the source and drain electrodes, to prevent metal oxidation and extraction, while maintaining minimal impact on carrier mobility by adjusting the distribution of this element to ensure it is more concentrated near the electrode interfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If oxide semiconductor is used in TFT to achieve low temperature manufacturing and high charge mobility, then manufacturing cost is reduced and charge mobility is improved, but the oxide semiconductor reacts with electrode metal causing deoxidation and cation extraction which deteriorates device reliability
Solution Approach 1:
A barrier layer is introduced as an intermediary between the oxide semiconductor and the electrode metal. This barrier layer prevents direct contact and chemical reaction between the two materials, stopping the deoxidation and cation extraction processes while allowing electrical functionality to be maintained.
Solution Approach 2:
The structure combines multiple materials with different properties: the oxide semiconductor layer for high charge mobility, the barrier layer for chemical stability and reaction prevention, and the electrode metal for electrical conduction. This composite structure resolves the contradiction by assigning different functions to different material layers.
2Area of stationary object
If oxide semiconductor is used to enable large-sized display manufacturing, then manufacturing scalability is improved, but metal leaching from the oxide semiconductor increases wiring resistance
Solution Approach 1:
The barrier layer acts as a protective intermediary that prevents metal atoms from leaching out of the oxide semiconductor into the wiring. This stops the degradation of wiring conductivity that would otherwise occur in large-sized displays where wiring lengths are greater.
3Device complexity
If oxide semiconductor contacts source and drain electrodes directly to simplify device structure, then device complexity is reduced, but reaction between oxide semiconductor and electrode material causes threshold voltage variation
Solution Approach 1:
The barrier layer is inserted between the oxide semiconductor and the source/drain electrodes. This simple additional layer prevents direct chemical reactions that cause threshold voltage shifts, while maintaining overall device structure simplicity.
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 effectively reduces metal extraction and oxidation, enhancing the reliability and stability of the TFT by minimizing the decrease in charge mobility and maintaining electrical performance.
Implementation Method 1
an added element with a second oxide formation free energy, the absolute value of the second oxide formation free energy being greater than or equal to the absolute value of the first oxide formation free energy
Data Source
AI summary
A thin-film transistor includes a gate electrode, a source electrode, a drain electrode, a gate insulation layer and an oxide semiconductor pattern. The source and drain electrodes include a first metal element with a first oxide formation free energy. The oxide semiconductor pattern has a first surface making contact with the gate insulation layer and a second surface making contact with the source and drain electrodes to be positioned at an opposite side of the first surface. The oxide semiconductor pattern includes an added element having a second oxide formation free energy having an absolute value greater than or equal to an absolute value of the first oxide formation free energy, wherein an amount of the added element included in a portion near the first surface is zero or smaller than an amount of the added element included in a portion near the second surface.