Oxide Semiconductor Thin Film Transistor Resistance Control
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Solution Overview
Problem
Existing semiconductor devices with oxide semiconductors face challenges in achieving stable electric characteristics and preventing increases in off current, particularly in thin film transistors, due to variations in resistance and conductivity.
Innovation Solution
A method involving heat treatment of an oxide semiconductor layer under a nitrogen atmosphere to reduce resistance, followed by the formation of a silicon oxide film using a sputtering method to create a high-resistance region, stabilizes the electric characteristics of the thin film transistor by controlling the conductivity of the oxide semiconductor layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If heat treatment is performed under nitrogen atmosphere to reduce resistance of oxide semiconductor layer, then electrical conductivity is improved, but resistance of contact regions increases excessively leading to unstable electric characteristics
Solution Approach 1:
The patent applies local quality by forming a silicon oxide film specifically in the region where the oxide semiconductor layer contacts the gate electrode layer. This creates a localized high-resistance region only at the contact interface, while the rest of the oxide semiconductor layer maintains its reduced resistance state from heat treatment. This selective modification stabilizes electric characteristics without excessively increasing contact resistance.
Solution Approach 2:
The patent uses composite materials by combining the oxide semiconductor layer with a silicon oxide film at the contact region. The silicon oxide film has different electrical properties (higher resistance) than the oxide semiconductor, and their combination creates a structured interface that controls resistance distribution. This composite structure prevents excessive resistance increase while maintaining stable electric characteristics.
2Power
If oxide semiconductor layer resistance is reduced through heat treatment, then on-current increases, but off-current increases due to insufficient resistance in contact regions
Solution Approach 1:
The silicon oxide film is formed locally only in the contact region between the oxide semiconductor layer and gate electrode layer. This localized high-resistance region blocks carrier leakage at the interface, reducing off-current. Meanwhile, the bulk oxide semiconductor layer maintains low resistance for high on-current, achieving both objectives simultaneously.
Solution Approach 2:
The silicon oxide film acts as an intermediary layer at the contact interface between the oxide semiconductor layer and gate electrode. It mediates the electrical interaction by providing a high-resistance barrier that prevents carrier leakage (reducing off-current) while allowing the oxide semiconductor to maintain its conductive properties for on-current flow.
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 a highly reliable thin film transistor with stable electric characteristics and reduced off current, enhancing the reliability and performance of semiconductor devices.
Implementation Method 1
heat treatment is performed under a nitrogen atmosphere after formation of the oxide semiconductor layer
Implementation Method 2
Resistance of the oxide semiconductor layer is reduced by heat treatment performed under a nitrogen atmosphere (that is, increase in electrical conductivity)
Implementation Method 3
a silicon oxide film is formed by a sputtering method so as to be in contact with a region which is in the oxide semiconductor layer subjected to heat treatment
Data Source
AI summary
An object is to provide a highly reliable semiconductor device including a thin film transistor having stable electric characteristics. In addition, another object is to manufacture a highly reliable semiconductor device at low cost with high productivity. In a method for manufacturing a semiconductor device including a thin film transistor including an oxide semiconductor layer as a channel formation region, the oxide semiconductor layer is heated under a nitrogen atmosphere to lower its resistance, thereby forming a low-resistance oxide semiconductor layer. Further, resistance of a region of the low-resistance oxide semiconductor layer, which is overlapped with a gate electrode layer, is selectively increased, thereby forming a high-resistance oxide semiconductor layer. Resistance of the oxide semiconductor layer is increased by forming a silicon oxide film in contact with the oxide semiconductor layer by a sputtering method.