Oxide Semiconductor TFT Dual Barrier Film Impurity Control
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Solution Overview
Problem
Thin-film transistors (TFTs) using oxide semiconductors face challenges in maintaining excellent transistor characteristics due to impurity and hydrogen diffusion, which affect the electrical resistance and stability of the oxide semiconductor layer.
Innovation Solution
A thin-film transistor structure is implemented with a first barrier film on the substrate and a second barrier film with hydrogen barrier properties between the first barrier film and the oxide semiconductor layer, where the first barrier film suppresses impurity diffusion and chemically reduces the oxide semiconductor layer, while the second barrier film reduces hydrogen diffusion, thereby maintaining the integrity and reducing electrical resistance of the oxide semiconductor layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single barrier film is used between the substrate and oxide semiconductor layer, then the structure is simple, but it cannot simultaneously block impurities from the substrate and prevent hydrogen diffusion into the oxide semiconductor layer
Solution Approach 1:
The barrier film is divided into two separate films: a first barrier film that blocks impurities from the substrate, and a second barrier film that prevents hydrogen diffusion into the oxide semiconductor layer. This segmentation allows each film to specialize in one protective function, resolving the contradiction between reliability and structural simplicity.
Solution Approach 2:
The first barrier film acts as an intermediary layer between the substrate and the oxide semiconductor layer, blocking impurities from the substrate while the second barrier film acts as an intermediary between the first barrier film and the oxide semiconductor layer, preventing hydrogen diffusion. This dual-intermediary approach ensures both protective functions are achieved.
2Ease of manufacture
If the first barrier film is in direct contact with the oxide semiconductor layer, then the manufacturing process is simple, but impurities from the substrate and hydrogen can degrade the oxide semiconductor layer
Solution Approach 1:
The barrier function is segmented into two separate films deposited in sequence: the first barrier film deposited on the substrate to block impurities, and the second barrier film deposited on the first barrier film to block hydrogen. This segmentation maintains manufacturing simplicity while eliminating harmful factor diffusion.
Solution Approach 2:
The first barrier film is deposited in advance on the substrate to block impurities before the oxide semiconductor layer is formed. The second barrier film is then deposited in advance on the first barrier film to prevent hydrogen diffusion. These preliminary actions prevent contamination before it occurs.
3Ease of manufacture
If no barrier films are used, then the manufacturing cost is low, but the oxide semiconductor layer suffers from impurity contamination and hydrogen-induced resistance increase
Solution Approach 1:
The barrier protection is segmented into two functional films: the first barrier film for impurity blocking and the second barrier film for hydrogen blocking. This segmentation provides comprehensive protection at minimal additional cost, maintaining manufacturing precision while keeping manufacturing cost low.
Solution Approach 2:
The two barrier films serve as intermediary protective layers between the substrate/environment and the oxide semiconductor layer, preventing both impurity contamination and hydrogen-induced resistance increase without significantly increasing manufacturing complexity or cost.
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 configuration ensures excellent transistor characteristics by preventing impurity and hydrogen-induced degradation, achieving stable and low electrical resistance in specific regions of the oxide semiconductor layer, thus enhancing the overall performance of TFTs.
Implementation Method 1
The first barrier film has a barrier property against an impurity from the substrate
Implementation Method 2
The first barrier film has a barrier property against an impurity from the substrate and a property of chemically reducing the oxide semiconductor layer
Implementation Method 3
the second barrier film is formed in a selective region on the first barrier film, and has a barrier property against hydrogen
Data Source
AI summary
Provided is a thin-film transistor that includes: a substrate; a first barrier film formed on the substrate; a second barrier film formed in a selective region on the first barrier film, and having a barrier property against hydrogen; an oxide semiconductor layer including a first part formed on the second barrier film and a second part formed on the first barrier film, in which the first part functions as an active layer, and the second part has lower electrical resistance than the first part; a gate electrode formed on the first part of the oxide semiconductor layer with a gate insulating film therebetween; and a source electrode or drain electrode electrically connected to the second part of the oxide semiconductor layer. The first barrier film has a barrier property against an impurity from the substrate and a property of chemically reducing the oxide semiconductor layer.