Oxide Semiconductor TFT Purification via Insulator Oxygen Supply
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Solution Overview
Problem
The electrical conductivity of oxide semiconductors used in thin film transistors is prone to variation due to deviations in stoichiometric composition and the presence of impurities like hydrogen, moisture, and hydroxyl groups during the thin film formation process, leading to unstable electric characteristics.
Innovation Solution
A method is employed to highly purify the oxide semiconductor layer by removing impurities such as hydrogen and moisture through an oxide insulating layer, introducing oxygen to the semiconductor layer, and performing heat treatment to achieve an intrinsic (i-type) semiconductor state, thereby stabilizing the electric characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If oxygen is introduced through the oxide insulating layer and heat treatment is performed to remove impurities, then the oxide semiconductor layer becomes highly purified and electrically intrinsic, but the process complexity and manufacturing steps increase
Solution Approach 1:
The oxide insulating layer is formed over the oxide semiconductor layer before final heat treatment, preparing the system in advance for controlled oxygen introduction and impurity removal during subsequent heating steps
Solution Approach 2:
The oxide insulating layer acts as an intermediary that enables controlled oxygen introduction to the oxide semiconductor layer during heat treatment, facilitating impurity removal while maintaining process control
2Manufacturing precision
If multiple heat treatment steps are performed at different temperatures and atmospheres, then impurity removal and oxygen supply are optimized, but the manufacturing time and energy consumption increase
Solution Approach 1:
The manufacturing process employs periodic heat treatment steps with alternating temperatures and atmospheres - first at 400-700°C in inert atmosphere for impurity removal, then at lower temperature for oxygen introduction, optimizing each phase separately
Solution Approach 2:
The process systematically changes physical parameters including temperature (400-700°C range), atmosphere (inert gas, oxygen, nitrogen), and duration for each heat treatment step to optimize impurity removal and oxygen supply efficiency
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
The method results in a transistor with stable electric characteristics and high reliability, as the intrinsic oxide semiconductor layer exhibits minimal temperature dependence and light-induced deterioration, with reduced off-state current and improved field-effect mobility.
Implementation Method 1
oxygen which is one of the main component of the oxide semiconductor and is reduced in the step of removing impurities, can be supplied from the oxide insulating layer containing oxygen to the oxide semiconductor layer
Implementation Method 2
heat treatment is performed. Through these steps of oxygen introduction and heat treatment, impurities such as hydrogen, moisture, a hydroxyl group, or hydride (also referred to as a hydrogen compound) are intentionally removed from the oxide semiconductor layer
Data Source
AI summary
In a transistor including an oxide semiconductor layer, an oxide insulating layer is formed so as to be in contact with the oxide semiconductor layer. Then, oxygen is introduced (added) to the oxide semiconductor layer through the oxide insulating layer, and heat treatment is performed. Through these steps of oxygen introduction and heat treatment, impurities such as hydrogen, moisture, a hydroxyl group, or hydride are intentionally removed from the oxide semiconductor layer, so that the oxide semiconductor layer is highly purified.