Oxide Semiconductor Thin Film Transistor Electrode Contact Resistance
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Solution Overview
Problem
Existing thin film transistors face challenges in reducing contact resistance between oxide semiconductor layers and source/drain electrode layers, limiting material choices for these electrodes and affecting process temperature limits.
Innovation Solution
A stacked-layer structure for source and drain electrode layers using oxides of metals with lower work functions than the oxide semiconductor layer, such as indium, zinc, or titanium, to form an optimal contact state, allowing for wider material choices and higher process temperature limits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single-layer source and drain electrode structure is used, then the device structure is simple, but the contact resistance between the electrode and oxide semiconductor layer is high
Solution Approach 1:
The source and drain electrode layers are divided into multiple sub-layers with different materials and functions. The first source/drain electrode layer (301a, 301b) provides optimal contact with the oxide semiconductor layer, while the second source/drain electrode layer (302a, 302b) provides structural support and electrical connection. This segmentation resolves the contradiction by creating a multi-layer structure that achieves low contact resistance while maintaining reasonable structural complexity.
Solution Approach 2:
The patent employs composite electrode structures combining different materials (e.g., In-Al-Zn-O-based oxide semiconductor with metal layers). The composite structure integrates the low contact resistance properties of oxide materials with the electrical conductivity and mechanical strength of metal layers, thereby reducing contact resistance while managing the increased structural complexity through systematic material combination.
2Temperature
If materials with high heat resistance are used for source and drain electrodes, then the process temperature limit is raised, but the contact resistance with oxide semiconductor layer increases
Solution Approach 1:
The electrode structure is segmented into functional layers: the first source/drain electrode layer (301a, 301b) made of materials with low work function (In-Al-Zn-O-based oxide semiconductor) provides optimal contact with the oxide semiconductor layer, while the second source/drain electrode layer (302a, 302b) made of high-heat-resistance materials (Al, Mo, W) provides structural support and withstands high process temperatures. This segmentation resolves the contradiction by assigning different thermal and electrical functions to different layers.
Solution Approach 2:
Different regions of the electrode structure have different material properties optimized for their specific functions. The region in direct contact with the oxide semiconductor layer (first source/drain electrode layer) uses materials with low work function and good interface properties, while regions requiring heat resistance (second source/drain electrode layer) use high-melting-point materials. This local quality differentiation resolves the contradiction between contact resistance and heat resistance.
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 effectively reduces contact resistance and allows for the use of high-heat-resistant materials, enhancing the electrical characteristics and reliability of thin film transistors.
Implementation Method 1
a thin layer, in the stacked-layer structure, is formed using an oxide of a metal whose work function is lower than the work function of an oxide semiconductor layer
Data Source
AI summary
An object is, in a thin film transistor including an oxide semiconductor layer, to reduce contact resistance between the oxide semiconductor layer and source and drain electrode layers electrically connected to the oxide semiconductor layer. The source and drain electrode layers have a stacked-layer structure of two or more layers in which a layer in contact with the oxide semiconductor layer is formed using an oxide of a metal whose work function is lower than the work function of the oxide semiconductor layer or an oxide of an alloy containing such a metal. Layers other than the layer in contact with the oxide semiconductor layer of the source and drain electrode layers are formed using an element selected from Al, Cr, Cu, Ta, Ti, Mo, or W, an alloy containing any of these elements as a component, an alloy containing any of these elements in combination, or the like.