Oxide Semiconductor TFT Channel Layer Protection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Oxide semiconductor channel layers in display panels are prone to oxygen deficiency due to additional manufacturing steps like CVD and plasma processes, affecting electrical properties such as starting voltage and sub-threshold swing.
Innovation Solution
The channel layer is positioned at the top of the TFT substrate with an over coating layer, avoiding damage and maintaining excellent electrical properties without the need for extra processing steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If extra manufacturing steps (CVD and plasma processes) are added to form the channel layer, then the electrical properties of the oxide semiconductor may be improved, but oxygen deficiency occurs causing starting voltage drift and sub-threshold swing increase
Solution Approach 1:
The patent removes the harmful CVD and plasma processes from the manufacturing sequence. By forming the oxide semiconductor layer before these processes, the channel layer is extracted from the harmful environment, preventing oxygen deficiency while maintaining excellent electrical properties.
Solution Approach 2:
The oxide semiconductor layer is formed in advance before the CVD and plasma processes. This preliminary action ensures the channel layer is already in place and protected, so subsequent manufacturing steps cannot cause oxygen deficiency. The gate electrode and gate insulating layer are formed after, creating a protective structure.
2Reliability
If poly-silicon is used for TFT channel, then mobility is improved (>100 Vs/cm2), but manufacturing cost increases
Solution Approach 1:
The patent changes the material parameter from poly-silicon to oxide semiconductor (a-IGZO). This material substitution maintains high mobility (10-20 Vs/cm2) while significantly reducing manufacturing cost, as oxide semiconductor can be formed using simpler sputtering processes without requiring the complex multi-step CVD and plasma treatments needed for poly-silicon.
3Ease of manufacture
If a-Si is used for TFT channel, then manufacturing cost is reduced, but mobility decreases
Solution Approach 1:
The patent uses a composite material approach by combining oxide semiconductor with specific metal elements (In, Ga, Zn) to create a-IGZO. This composite material achieves a balance between low manufacturing cost (comparable to a-Si) and improved mobility (10-20 Vs/cm2), surpassing conventional a-Si performance while maintaining cost-effectiveness.
4Device complexity
If the channel layer is formed using conventional methods, then the TFT structure is complete, but the channel layer is damaged causing poor electrical properties
Solution Approach 1:
The patent applies beforehand cushioning by forming the gate insulating layer and gate electrode over the oxide semiconductor channel layer. This protective structure cushions and protects the channel layer from subsequent manufacturing processes, preventing damage and maintaining excellent electrical properties throughout the remaining fabrication steps.
Data Source
AI summary
A display panel comprising a TFT substrate, a display medium and an opposite substrate is provided. The display medium is disposed between the TFT substrate and the opposite substrate. The TFT substrate comprises a substrate, a first electrode layer, a pixel electrode layer, a first insulating layer, a second electrode layer, a second insulating layer, a channel layer and an over coating layer. The first electrode layer and the pixel electrode layer are disposed on the substrate. The first insulating layer is disposed on the first electrode layer and the pixel electrode layer. The second electrode layer is disposed on the first insulating layer. The second insulating layer is disposed on the second electrode layer. The channel layer is interposed into a first contact hole and a second contact hole to electrically connect the first electrode layer. The over coating layer is disposed on the channel layer.