Indium Contact Layer Reduces Oxide Semiconductor 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 the performance of electronic devices like liquid crystal displays.
Innovation Solution
Implementing a stacked structure for source and drain electrode layers with a thin indium or indium-alloy layer in contact with the oxide semiconductor layer, or using a zinc or zinc-alloy layer, which reduces contact resistance and allows for the use of high-heat-resistant materials, thereby improving the contact state and extending material choices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single-layer source/drain electrode structure is used, then the structure is simple, but contact resistance with the oxide semiconductor layer is high
Solution Approach 1:
The source/drain electrode is divided into multiple layers with distinct functions: a first electrode layer in direct contact with the oxide semiconductor layer and a second electrode layer above it. This segmentation allows each layer to be optimized for its specific role, with the first layer providing low contact resistance through material selection (e.g., indium oxide, zinc oxide) and the second layer providing structural support and electrical connectivity.
Solution Approach 2:
The patent employs composite material structures where the first electrode layer uses materials with high affinity for oxide semiconductors (such as indium oxide, zinc oxide, or their alloys) to minimize contact resistance, while the second electrode layer may use different materials optimized for conductivity and mechanical properties. This composite approach resolves the contradiction by combining materials with complementary properties.
2Temperature
If high-heat-resistant materials are used for source/drain electrodes, then temperature process limits are raised, but contact resistance with oxide semiconductor layer increases
Solution Approach 1:
The electrode structure is segmented into a first layer that directly contacts the oxide semiconductor (using materials like indium oxide or zinc oxide that provide low contact resistance) and a second layer that can use high-heat-resistant materials (such as tungsten, molybdenum, or their alloys). This allows the process temperature limit to be raised by the second layer while the first layer maintains optimal electrical contact.
Solution Approach 2:
The first electrode layer acts as an intermediary between the oxide semiconductor and the high-heat-resistant second electrode layer. This intermediary layer has dual functionality: it provides low contact resistance to the oxide semiconductor while also serving as a barrier that allows the second layer to use high-temperature materials without directly contacting the semiconductor.
3Adaptability or versatility
If material choices for source/drain electrodes are limited, then manufacturing is simpler, but transistor performance is reduced
Solution Approach 1:
The electrode structure is divided into layers that can be independently optimized. The first layer can use materials specifically selected for low contact resistance with oxide semiconductors (indium oxide, zinc oxide, indium zinc oxide), while the second layer can use materials selected for other properties (conductivity, heat resistance, mechanical strength). This segmentation enables broad material choice flexibility without requiring complex manufacturing processes, as each layer can be deposited using standard techniques.
Solution Approach 2:
The multi-layer electrode structure serves multiple functions simultaneously: the first layer provides low contact resistance, the second layer provides structural support and electrical connectivity, and the combination enables both material versatility and manufacturing simplicity. This multi-functionality allows the same basic structure to accommodate various material combinations for different application requirements.
Data Source
AI summary
An object is to reduce contact resistance between an oxide semiconductor layer and source and drain electrode layers electrically connected to the oxide semiconductor layer in a thin film transistor including the oxide semiconductor layer. The source and drain electrode layers have a stacked structure of two or more layers. In this stack of layers, a layer in contact with the oxide semiconductor layer is a thin indium layer or a thin indium-alloy layer. Note that the oxide semiconductor layer contains indium. A second layer or second and any of subsequent layers in the source and drain electrode layers are formed using an element selected from Al, Cr, Cu, Ta, Ti, Mo, and W, an alloy containing any of these elements as a component, an alloy containing any of these elements in combination, or the like.