Metallic Source Drain Thin Film Transistor Fabrication
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Solution Overview
Problem
Conventional thin film transistors with polysilicon source and drain materials require longer production time, higher costs, and result in high contact resistance, which can lead to signal transmission delays in larger liquid crystal display panels, compromising display quality.
Innovation Solution
A method of fabricating thin film transistors with metallic sources and drains, using a substrate with a patterned polysilicon layer, forming a metal layer, and removing portions to create sources and drains through photolithographic and etching processes, eliminating the need for ion implantation and annealing, and using materials like aluminum, copper, or molybdenum.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ion implantation is used to form source and drain in polysilicon layer, then the thin film transistor can be fabricated, but the production time increases and cost increases
Solution Approach 1:
The patent extracts and eliminates the ion implantation step from the fabrication process. Instead of using ion implantation to form source and drain regions in polysilicon, the invention directly forms metallic source and drain electrodes on the substrate, removing the time-consuming ion implantation and annealing processes while still achieving the desired thin film transistor structure and functionality
Solution Approach 2:
The patent replaces the expensive and time-consuming polysilicon ion implantation process with a simpler, more cost-effective metallic electrode deposition process. The metallic source and drain electrodes are directly formed using standard deposition techniques, eliminating the need for complex ion implantation equipment and multiple processing steps
2Reliability
If ion implantation is used to form source and drain in polysilicon layer, then the thin film transistor can be fabricated, but the production cost increases
Solution Approach 1:
The patent extracts and eliminates the ion implantation step from the fabrication process. Instead of using ion implantation to form source and drain regions in polysilicon, the invention directly forms metallic source and drain electrodes on the substrate, removing the time-consuming ion implantation and annealing processes while still achieving the desired thin film transistor structure and functionality
Solution Approach 2:
The patent replaces the expensive and time-consuming polysilicon ion implantation process with a simpler, more cost-effective metallic electrode deposition process. The metallic source and drain electrodes are directly formed using standard deposition techniques, eliminating the need for complex ion implantation equipment and multiple processing steps
3Reliability
If polysilicon material is used for source and drain, then the thin film transistor can be fabricated, but the contact resistance between source/drain and metal contact layer is high
Solution Approach 1:
The patent applies homogeneity by making the source and drain electrodes themselves metallic, matching the material type of the metal contact layers. This eliminates the material interface between polysilicon and metal, creating a homogeneous metallic-to-metallic contact that significantly reduces contact resistance compared to the heterogeneous polysilicon-to-metal interface
Solution Approach 2:
The patent uses composite material strategy by forming a stacked structure of different metallic materials for source and drain electrodes. This allows optimization of each layer's properties - using materials with appropriate work functions, conductivity, and adhesion characteristics to minimize contact resistance and improve overall device performance
4Reliability
If high contact resistance exists between source/drain and metal contact layer, then the thin film transistor can operate, but the signal transmission speed decreases in large panels
Solution Approach 1:
The patent applies homogeneity by making the source and drain electrodes themselves metallic, matching the material type of the metal contact layers. This eliminates the material interface between polysilicon and metal, creating a homogeneous metallic-to-metallic contact that significantly reduces contact resistance compared to the heterogeneous polysilicon-to-metal interface
Solution Approach 2:
The patent uses composite material strategy by forming a stacked structure of different metallic materials for source and drain electrodes. This allows optimization of each layer's properties - using materials with appropriate work functions, conductivity, and adhesion characteristics to minimize contact resistance and improve overall device performance
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 reduces contact resistance, shortens production time, and lowers costs, enabling improved signal transmission and display quality in liquid crystal displays.
Implementation Method 1
forming a metal layer, and removing portions to create sources and drains through photolithographic and etching processes
Implementation Method 2
removing portions to create sources and drains through photolithographic and etching processes
Data Source
AI summary
A method of fabricating a thin film transistor is disclosed. First, a substrate is provided and a patterned polysilicon layer is formed on the substrate. A metal layer is formed on the patterned polysilicon layer. Then, a portion of the metal layer is removed so that the remaining metal layer beside the patterned polysilicon layer forms a source and a drain. A gate insulation layer is formed on the substrate to cover the source, the drain and the patterned polysilicon layer. A gate is formed on the gate insulation layer over the patterned polysilicon layer.