Oxide Semiconductor Thin Film Transistor Ohmic Contact
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Solution Overview
Problem
Conventional thin film transistors using silicon-based semiconductors are not transparent to visible light, leading to operation errors and requiring complex structures and manufacturing processes, while those using ZnO-based transparent conductive oxide films lack ohmic contact between the oxide semiconductor layer and electrodes.
Innovation Solution
A method involving the formation of a second insulating film over an oxide semiconductor layer in an oxidative-gas-containing atmosphere, patterning to expose contact regions, and lowering the electric resistance of these regions to create ohmic contact areas for the source and drain electrodes, eliminating the need for an ohmic contact layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a silicon-based semiconductor layer is used for the channel layer, then the transistor can be formed with conventional manufacturing processes, but the device absorbs visible light causing operation errors and requires a complex screening layer structure
Solution Approach 1:
The patent changes the material composition parameter from silicon-based to zinc oxide-based semiconductor, which fundamentally alters the optical properties to achieve transparency while maintaining electrical functionality. This parameter change eliminates the need for screening layers while preserving transistor operation.
Solution Approach 2:
The patent extracts and removes the screening layer from the device structure by using a transparent zinc oxide semiconductor material that inherently allows visible light transmission. This extraction simplifies the overall device structure while maintaining electrical performance.
2Device complexity
If a zinc oxide-based transparent conductive oxide film is used for the channel layer, then the device becomes transparent to visible light and can be formed at low temperature, but the oxide semiconductor layer lacks ohmic contact with the electrodes
Solution Approach 1:
The patent applies local quality by forming an ohmic contact layer specifically at the electrode contact regions of the zinc oxide semiconductor, while maintaining the intrinsic properties of the channel region. This localized modification ensures good electrical contact without compromising the transparency and low-temperature formation characteristics of the overall device.
Solution Approach 2:
The patent introduces an ohmic contact layer as an intermediary material between the zinc oxide semiconductor and the metal electrodes. This intermediary layer facilitates reliable electrical contact while allowing the zinc oxide channel to maintain its transparent and low-temperature formable properties.
3Reliability
If an ohmic contact layer is formed on the oxide semiconductor layer to establish good contact with electrodes, then the contact quality improves, but the manufacturing steps increase
Solution Approach 1:
The patent merges the formation of the ohmic contact layer with the existing electrode formation step in the manufacturing process. By combining these operations, the patent achieves good electrical contact without adding separate processing steps, thereby maintaining manufacturing efficiency while improving contact quality.
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 approach enables the production of thin film transistors with good ohmic contact between the oxide semiconductor layer and electrodes, minimizing manufacturing steps and ensuring excellent transistor characteristics, including a low OFF current and high ON/OFF ratio.
Implementation Method 1
forming an oxide semiconductor layer on the gate insulating film
Implementation Method 2
forming a second insulating film on the oxide semiconductor layer in an oxidative-gas-containing atmosphere
Implementation Method 3
patterning the second insulating film to expose a pair of contact regions in the oxide semiconductor layer
Implementation Method 4
the region thereof where the semiconductor layer is brought into contact with electrodes is subjected to a resistance-lowering treatment
Data Source
AI summary
A thin film transistor is manufactured by forming a gate electrode on a substrate, forming a first insulating film on the gate electrode, forming an oxide semiconductor layer on the first insulating film with an amorphous oxide, patterning the first insulating film, patterning the oxide semiconductor layer, forming a second insulating film on the oxide semiconductor layer in an oxidative-gas-containing atmosphere, patterning the second insulating film to expose a pair of contact regions, forming an electrode layer on the pair of contact regions, and patterning the electrode layer to for a source electrode and a drain electrode.