Oxide TFT Gate Insulator Oxygen Treatment for Stable LCD Interfaces
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Solution Overview
Problem
Thin film transistors using oxide semiconductor films, particularly those with indium (In), gallium (Ga), and zinc (Zn), face issues with interface instability, contact resistance, and variation in electrical characteristics, leading to reliability concerns and display unevenness in liquid crystal and light-emitting display devices.
Innovation Solution
The implementation of an oxygen radical treatment on the gate insulating layer to create an oxygen-excess region, combined with the use of oxygen-excess and oxygen-deficient oxide semiconductor films, enhances the interface characteristics and reduces contact resistance, thereby improving the reliability and operational stability of the thin film transistors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a thin film transistor with oxide semiconductor film is used, then lower driving voltage and simpler manufacturing are achieved, but interface instability and reliability issues occur
Solution Approach 1:
The gate insulating layer is subjected to oxygen radical treatment before the oxide semiconductor film is formed. This preliminary oxygen enrichment creates an oxygen-excess region at the interface, which prevents oxygen deficiency and instability that would otherwise occur during subsequent manufacturing steps, thereby ensuring interface stability while maintaining manufacturing simplicity
Solution Approach 2:
The oxygen concentration in the gate insulating layer is changed by exposing it to oxygen radicals, transforming the layer from having insufficient oxygen to having an oxygen-excess region at the interface. This parameter change (oxygen concentration) directly addresses the interface instability problem while keeping the manufacturing process simple
2Loss of energy
If low resistance metal material is used for source and drain electrodes, then electrical resistance is reduced, but contact resistance increases due to Schottky junction formation
Solution Approach 1:
An oxygen-excess region is created in the gate insulating layer at the interface with the oxide semiconductor film. This oxygen-excess region acts as an intermediary that prevents Schottky junction formation between the low resistance metal electrodes and the semiconductor, thereby reducing contact resistance while maintaining low electrical resistance
Solution Approach 2:
The oxygen concentration parameter in the gate insulating layer is increased through oxygen radical treatment, creating an oxygen-excess region. This parameter change modifies the electrical characteristics at the interface, preventing Schottky junction formation and reducing contact resistance
3Ease of manufacture
If hydrogen is present in the gate insulating layer, then manufacturing is easier, but hydrogen diffuses and reacts with oxygen to form H2O, reducing reliability
Solution Approach 1:
Oxygen radical treatment is performed on the gate insulating layer before it contacts the oxide semiconductor film. This preliminary action creates an oxygen-excess region that acts as a barrier, preventing hydrogen from diffusing into the semiconductor and reacting with oxygen to form H2O, thereby maintaining both manufacturing ease and reliability
Solution Approach 2:
The oxygen-excess region created by oxygen radical treatment serves as a preliminary countermeasure against hydrogen diffusion. The excess oxygen prevents the harmful reaction between hydrogen and oxygen by creating an oxygen-rich environment that blocks hydrogen penetration, thus preventing reliability issues
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 results in thin film transistors with reduced contact resistance, improved interface stability, and minimized variation in electrical characteristics, leading to enhanced reliability and performance in display devices.
Implementation Method 1
a gate insulating layer formed over the gate electrode layer; a surface of the gate insulating layer is subjected to oxygen radical treatment
Data Source
AI summary
An object is to provide favorable interface characteristics of a thin film transistor including an oxide semiconductor layer without mixing of an impurity such as moisture. Another object is to provide a semiconductor device including a thin film transistor having excellent electric characteristics and high reliability, and a method by which a semiconductor device can be manufactured with high productivity. A main point is to perform oxygen radical treatment on a surface of a gate insulating layer. Accordingly, there is a peak of the oxygen concentration at an interface between the gate insulating layer and a semiconductor layer, and the oxygen concentration of the gate insulating layer has a concentration gradient. The oxygen concentration is increased toward the interface between the gate insulating layer and the semiconductor layer.