Oxide Semiconductor TFT Oxygen Ion Injection Annealing
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Solution Overview
Problem
Oxide semiconductor thin film transistors have high carrier density due to oxygen deficiency, leading to high current flow in depletion mode and instability from external factors, requiring larger negative gate voltage for turn-off and a stable passivation layer to maintain electrical characteristics.
Innovation Solution
A method of manufacturing an oxide semiconductor thin film transistor involving a plasma process with oxygen ions, followed by an annealing process at 150°C - 500°C, and the use of a passivation layer such as silicon oxide or silicon nitride to stabilize the channel layer by injecting oxygen ions through the passivation layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a silicon nitride layer is used as a passivation layer, then more functionality as passivation against water or oxygen is achieved, but deoxidation of the oxide semiconductor occurs due to large amount of hydrogen, generating high leakage current
Solution Approach 1:
A silicon oxide layer is introduced as an intermediary barrier between the silicon nitride passivation layer and the oxide semiconductor channel. The silicon oxide layer has lower hydrogen content compared to silicon nitride, preventing hydrogen-induced deoxidation of the channel while still allowing the silicon nitride layer to provide effective passivation against water and oxygen. This mediator structure resolves the contradiction by decoupling the passivation function from the hydrogen contamination source.
2Reliability
If oxygen ions are injected into the channel layer, then carrier density is reduced and threshold voltage is improved, but additional process steps are required
Solution Approach 1:
The oxygen ion injection process is combined with the existing plasma treatment step in the manufacturing process. Instead of adding a separate oxygen injection step, the plasma process is configured to generate oxygen ions that are simultaneously used for both surface cleaning and oxygen implantation into the channel layer. This merging of functions achieves the desired electrical characteristic stabilization without significantly increasing process complexity.
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
The method stabilizes the oxide semiconductor thin film transistor by reducing carrier density and maintaining a desirable threshold voltage, enhancing reliability and reducing power consumption by achieving a more positive threshold voltage.
Implementation Method 1
A gas used in the plasma process may include oxygen ions. The plasma process may be an N2O plasma process.
Implementation Method 2
Ions containing oxygen is injected into the channel layer. The ion injection process is performed by injecting ions containing oxygen to the channel layer through the passivation layer using an ion injection apparatus.
Implementation Method 3
An annealing process is performed, after the ion injection process. The annealing process may be performed at a temperature of approximately 150°C - 500°C.
Data Source
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AI summary
Methods of manufacturing an oxide semiconductor thin film transistor are provided. The methods include forming a gate on a substrate, and a gate insulating layer on the substrate to cover the gate. A channel layer, which is formed of an oxide semiconductor, may be formed on the gate insulating layer. Source and drain electrodes may be formed on opposing sides of the channel layer. The method includes forming supplying oxygen to the channel layer, forming a passivation layer to cover the source and drain electrodes and the channel layer, and performing an annealing process after forming the passivation layer.