Oxide Semiconductor TFT Surface Oxidation Plasma Damage
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Solution Overview
Problem
ZnO based semiconductor thin film transistors are prone to damage from plasma during manufacturing, leading to increased carrier density and shifts in threshold voltage, resulting in leakage currents, especially when the channel is exposed to high-energy plasma used for patterning source and drain electrodes.
Innovation Solution
A method of manufacturing oxide semiconductor thin film transistors that involves forming an oxide semiconductor channel layer and source/drain electrodes on a substrate, followed by oxidizing the channel layer surface using an oxidizing material, such as a liquid oxidizing agent or self-assembled monolayer, and forming a passivation layer with functional groups to control carrier density and prevent plasma damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If high-energy plasma is used for patterning source and drain electrodes, then patterning precision is improved, but the channel is damaged leading to increased carrier density and threshold voltage shift
Solution Approach 1:
A protective layer is formed on the channel surface before the plasma patterning process. This preliminary protective action prevents plasma damage to the channel while allowing high-energy plasma to be used for precise patterning of source and drain electrodes.
Solution Approach 2:
The protective layer acts as an intermediary between the plasma and the channel. It absorbs or blocks the harmful plasma energy while allowing the patterning process to proceed, thus mediating between the need for precise patterning and the need to protect the channel from damage.
2Ease of manufacture
If the channel is exposed to plasma during manufacturing, then source and drain electrodes can be patterned, but carrier density on the channel surface increases causing leakage current
Solution Approach 1:
The protective layer is applied before plasma exposure to prevent carrier density increase on the channel surface. This allows the subsequent electrode patterning process to proceed without causing leakage current issues.
Solution Approach 2:
The protective layer that would normally be removed as waste is actually beneficial as it prevents plasma-induced carrier density increase. The potential harm of plasma exposure is converted into a benefit by using the protective layer as a shield during the necessary patterning process.
3Object-affected harmful factors
If additional protective layers and oxidizing steps are added to prevent plasma damage, then channel protection is improved, but fabrication process complexity increases
Solution Approach 1:
The protective function is merged with the passivation layer that is already part of the device structure. By forming the protective layer using the same PVD process as the channel, and integrating it with the passivation layer formation, the solution adds minimal process steps while providing comprehensive protection.
Solution Approach 2:
The protective layer serves multiple functions: it protects the channel from plasma damage, controls carrier density, and works together with the passivation layer for overall device protection. This multi-functionality reduces the need for separate dedicated protective structures.
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 method effectively controls carrier density on the channel surface, simplifies the fabrication process, and reduces fabrication costs by minimizing plasma-induced damage, thereby maintaining desirable electrical characteristics and preventing leakage currents.
Implementation Method 1
oxidizing a surface of the channel layer by placing an oxidizing material in contact with the surface of the channel layer
Implementation Method 2
forming a passivation layer, which covers the channel and the source and drain, using a material including a functional group capable of oxidizing the channel layer
Implementation Method 3
the channel layer may be formed using a physical vapor deposition (PVD) method including a sputtering method and an evaporation method
Data Source
AI summary
Oxide semiconductor thin film transistors (TFT) and methods of manufacturing the same are provided. The methods include forming a channel layer on a substrate, forming source and drain electrodes at opposing sides of the channel layer, and oxidizing a surface of the channel layer by placing an oxidizing material in contact with the surface of the channel layer, reducing carriers on the surface of the channel layer. Due to the oxidizing agent treatment of the surface of the channel layer, excessive carriers that are generated naturally, or during the manufacturing process, may be more effectively controlled.