Oxide TFT Barrier Layer for Ohmic Contact
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Solution Overview
Problem
Conventional thin film transistors (TFTs) using oxide semiconductors face issues with forming and maintaining ohmic contact between the channel layer and electrodes, particularly when using metals like copper, due to oxidation reactions that degrade TFT properties.
Innovation Solution
Incorporating a barrier layer made from materials like Ti, Mo, W, Nb, Ta, Cr, or their nitrides or alloys between the oxide semiconductor channel layer and the electrodes to prevent direct contact and oxidation, ensuring electrical connection while maintaining ohmic contact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If copper is used to form electrodes in touch with the oxide semiconductor channel layer, then low resistance and high-speed operation are achieved, but the copper bonds with oxygen in the oxide semiconductor, converting the oxide semiconductor into an N-type semiconductor and deteriorating TFT properties
Solution Approach 1:
A barrier layer made of titanium (Ti) or its alloy is introduced as an intermediary between the copper electrode and the oxide semiconductor channel layer. This barrier layer prevents direct contact between copper and oxygen in the oxide semiconductor, thereby preventing the harmful oxidation reaction while maintaining electrical connection. The barrier layer acts as a mediator that allows charge transfer but blocks oxygen diffusion, resolving the contradiction between achieving low resistance and preventing oxidation.
2Reliability
If a barrier layer is introduced between the electrode and channel layer to prevent oxidation, then TFT properties are maintained, but the device structure becomes more complex
Solution Approach 1:
The barrier layer is applied locally only at the critical interface between the electrode and the oxide semiconductor channel layer, rather than throughout the entire device. This localized approach prevents oxidation where it matters most while minimizing the overall structural complexity. The barrier layer is confined to the specific region where the harmful oxidation reaction occurs, allowing the rest of the device structure to remain simple and manageable.
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 enables the formation and maintenance of ohmic contact between the channel layer and electrodes, enhancing TFT properties by preventing oxidation and ensuring low resistance, thus enabling high-speed and high-resolution display applications.
Implementation Method 1
a first barrier layer made from at least one selected from the group consisting of Ti, Mo, W, Nb, Ta, Cr, nitrides thereof, and alloys thereof, the first barrier layer being in touch with the first electrode and the channel layer and separating the first electrode from the channel layer
Data Source
AI summary
The present invention provides a thin film transistor including an oxide semiconductor layer (4) for electrically connecting a signal electrode (6a) and a drain electrode (7a), the an oxide semiconductor layer being made from an oxide semiconductor; and a barrier layer (6b) made from at least one selected from the group consisting of Ti, Mo, W, Nb, Ta, Cr, nitrides thereof, and alloys thereof, the barrier layer (6b) being in touch with the signal electrode (6a) and the oxide semiconductor layer (4) and separating the signal electrode (6a) from the oxide semiconductor layer (4). Because of this configuration, the thin film transistor can form and maintain an ohmic contact between the first electrode and the channel layer, thereby being a thin film transistor with good properties.