Oxide Semiconductor TFT Contact Resistance Reduction
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Solution Overview
Problem
The contact resistance between the drain electrode and the transparent conductive layer in oxide semiconductor TFTs increases due to the oxide film formed on the drain electrode surface during N2O plasma treatment, affecting the TFT characteristics.
Innovation Solution
A semiconductor device with a copper oxide film between the source and drain electrodes and the interlayer insulating layer, where the transparent conductive layer is in direct contact with the copper layer in the contact hole without the copper oxide film, and the copper oxide film is selectively removed using chelate cleaning to flatten the interface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If N2O plasma treatment is performed on the oxide semiconductor layer to suppress deterioration of TFT characteristics, then TFT characteristics are improved, but the drain electrode surface is oxidized forming a copper oxide film that increases contact resistance
Solution Approach 1:
The invention applies different surface conditions to different regions: the oxide semiconductor layer surface is oxidized to suppress deterioration, while the drain electrode surface is kept reduced to maintain low contact resistance. This is achieved by performing plasma treatment under conditions that selectively oxidize the oxide semiconductor layer without significantly oxidizing the copper drain electrode surface.
Solution Approach 2:
The invention creates an asymmetric surface condition where the oxide semiconductor layer has an oxidized surface while the copper electrode has a reduced surface. This asymmetry is achieved through controlled plasma treatment parameters that exploit the different oxidation behaviors of the oxide semiconductor and copper materials.
2Object-affected harmful factors
If the copper oxide film is removed by chelate cleaning to reduce contact resistance, then contact resistance is reduced, but the interface between drain electrode and transparent conductive layer becomes uneven
Solution Approach 1:
The invention changes the chemical parameters of the plasma treatment to selectively remove copper oxide while preserving the underlying copper surface. By adjusting plasma power, gas composition, and treatment time, the process removes the harmful oxide layer while maintaining surface flatness suitable for subsequent transparent conductive layer formation.
Solution Approach 2:
The invention uses plasma as a strong oxidizing environment to selectively remove copper oxide through controlled oxidation-reduction reactions. The plasma treatment oxidizes the copper oxide film making it removable, while the controlled nature of the process prevents excessive surface roughening.
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 configuration suppresses the increase in contact resistance while maintaining TFT characteristics, ensuring reliable and consistent performance by removing the copper oxide film to achieve a flatter interface between the drain electrode and the transparent conductive layer.
Implementation Method 1
the exposed electrode surface may possibly be exposed to the N2O plasma and oxidized. For example, Patent Document 1 states that when copper (Cu) or a Cu alloy is used as the electrode material, an oxide film may be formed on the electrode surface through the N2O plasma treatment.
Implementation Method 2
the copper oxide film is selectively removed using chelate cleaning to flatten the interface
Data Source
AI summary
A semiconductor device (100A) is provided with: a gate electrode (3); an oxide semiconductor layer (5); a thin-film transistor (101) including a gate insulating layer (4), a source electrode (7S), and a drain electrode (7D); an inter-layer insulating layer (11) arranged so as to cover the thin-film transistor (101) and come into contact with a channel area (5c) of the thin-film transistor (101); and a transparent electroconductive layer (19) arranged on the inter-layer insulating layer (11), the source electrode (7S) and the drain electrode (7D) each having a copper layer (7a), and the device being further provided with a copper oxide film (8) arranged between the source and drain electrodes and the inter-layer insulating layer (11). The inter-layer insulating layer (11) covers the drain electrode (7D) with the copper oxide film (8) interposed therebetween. The transparent electroconductive layer (19) is directly connected to the copper layer (7a) of the drain electrode (7D) inside a contact hole (CH1) formed in the inter-layer insulating layer (11), without the copper oxide film (8) being interposed therebetween.