Oxide Semiconductor TFT With Layered Source Drain Electrodes
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Solution Overview
Problem
In traditional TFT-LCDs, the use of amorphous silicon as an active layer leads to increased resistance when in contact with metal electrodes, requiring additional ohmic contact silicon layers, while oxide semiconductors, though offering faster carrier mobility, are unstable during etching, necessitating an insulating layer that complicates the TFT structure and increases production costs.
Innovation Solution
A thin film transistor structure where the source and drain electrodes are disposed on different layers, isolated by a semiconductor connecting section made of oxide semiconductor material, eliminating the need for additional insulating layers and simplifying the manufacturing process by ensuring stable etching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If oxide semiconductor material is used as the active layer, then carrier mobility is improved (more than 10 times faster than amorphous silicon), but the etching stability deteriorates (etching speed is faster than source and drain metal electrodes, causing the oxide semiconductor layer to be etched together with the metal electrodes)
Solution Approach 1:
The source and drain electrodes are disposed on different layers (first layer and second layer) rather than the same layer, creating a three-dimensional stacked structure. This dimensional change allows the oxide semiconductor active layer to be positioned between the electrodes without requiring additional insulating layers, as the vertical stacking naturally provides the necessary isolation and contact geometry.
2Stability of the object's composition
If an insulating layer is added to protect the oxide semiconductor during etching, then etching stability is improved, but device complexity increases (insulating layer always disposed between source and drain electrodes and active layer)
Solution Approach 1:
The harmful insulating layer that complicates the TFT hierarchy is extracted/removed from the structure. Instead of adding an insulating layer between the active layer and electrodes, the patent uses a different layering approach where source and drain electrodes are on different layers, eliminating the need for the problematic insulating layer while maintaining etching stability.
Solution Approach 2:
By transitioning from a planar two-dimensional layout to a three-dimensional stacked structure with source and drain electrodes on different layers, the patent achieves both etching stability and reduced complexity without requiring additional insulating layers between the active layer and electrodes.
3Reliability
If ohmic contact silicon layer containing phosphorus is added between amorphous silicon and metal electrodes, then contact resistance is reduced, but device complexity increases
Solution Approach 1:
The additional ohmic contact silicon layer containing phosphorus is extracted/removed from the structure. The patent achieves low contact resistance directly through the oxide semiconductor active layer's inherent properties and the optimized three-dimensional geometry of electrode contacts, eliminating the need for this additional doped layer.
Data Source
AI summary
A thin-film transistor (TFT) comprises a gate electrode, a gate insulating layer, a source electrode and a drain electrode which are formed on a base substrate, the source electrode and the drain electrode are disposed on different layers and isolated from each other through a semiconductor connecting section made of an oxide semiconductor material; a position of the semiconductor connecting section corresponds to a position of the gate electrode; and at least one part of the source electrode and at least one part of the drain electrode overlap each other at a position corresponding to the semiconductor connecting section. A display device comprising the TFT and a display device comprising the display device are also disclosed.