Oxide Connecting Layer for Corrosion-Free Semiconductor Electrodes
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Solution Overview
Problem
The existing manufacturing process for TFT substrates is complicated due to the need for multiple photomasks and masks to pattern both lower and upper films simultaneously, leading to increased complexity and the risk of electrolytic corrosion between metal electrodes and transparent conductive layers.
Innovation Solution
A semiconductor device with an oxide semiconductor layer and a protective layer, where a metal layer is interposed between the substrate and the transparent conductive layer, connected via an oxide connecting layer formed from the same oxide film as the semiconductor layer, reducing the risk of electrolytic corrosion and simplifying the manufacturing process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a multilayer structure with barrier metal and aluminum is used for source and drain electrodes, then aluminum diffusion into the semiconductor layer is prevented, but the manufacturing process becomes more complex requiring multiple photomasks
Solution Approach 1:
An oxide connecting layer is introduced as an intermediary between the aluminum electrode and the semiconductor layer. This oxide layer serves as a diffusion barrier, preventing aluminum from migrating into the semiconductor layer while allowing electrical conduction. This resolves the contradiction by providing the necessary protection without requiring a complex multilayer metal structure with multiple photomasks.
Solution Approach 2:
The invention changes the material parameter at the interface between the electrode and semiconductor layer from a metal-barrier metal-metal structure to a metal-oxide-semiconductor structure. By changing the intermediate layer from metal to oxide, the diffusion barrier function is achieved while simplifying the manufacturing process to require only a single photomask for patterning the electrode.
2Reliability
If aluminum film is allowed to contact with transparent conductive film during wet etching, then electrolytic corrosion occurs causing increased contact resistance, but using barrier metal adds process complexity
Solution Approach 1:
The oxide connecting layer acts as a mediator between the aluminum electrode and the transparent conductive film (such as ITO). During wet etching processes, this oxide layer prevents direct contact between aluminum and the transparent conductive material, thereby preventing electrolytic corrosion reactions. This maintains low contact resistance while avoiding the complexity of multilayer barrier metal structures.
3Ease of manufacture
If oxide connecting layer is used instead of barrier metal layer, then electrolytic corrosion is prevented and manufacturing process is simplified, but electrical resistance might increase
Solution Approach 1:
The oxide connecting layer is formed by controlling the oxidation state and composition to achieve optimal electrical conductivity. By adjusting parameters such as oxygen content, thickness, and crystalline structure of the oxide layer, the electrical resistance is kept low enough for practical applications while maintaining the corrosion prevention and manufacturing simplification benefits.
Data Source
AI summary
This semiconductor device (101) includes: a substrate (1); a thin-film transistor (10) which includes an oxide semiconductor layer (6) as its active layer; a protective layer (11) covering the thin-film transistor; a metal layer (9d, 9t) interposed between the protective layer (11) and the substrate (1); a transparent conductive layer (13, 13t) formed on the protective layer (11); and a connecting portion (20, 30) to electrically connect the metal layer (9d, 9t) and the transparent conductive layer (13, 13t) together. The connecting portion (20, 30) includes an oxide connecting layer (6a, 6t) which is formed out of a same oxide film as a oxide semiconductor layer (6) and which has a lower electrical resistance than the oxide semiconductor layer (6). The metal layer (9d, 9t) is electrically connected to the transparent conductive layer (13, 13t) via the oxide connecting layer (6a, 6t).