Oxide Semiconductor TFT Channel Crystallization With Low-Temperature Annealing
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Solution Overview
Problem
Conventional semiconductor devices using crystalline silicon for TFTs in liquid crystal and electroluminescence displays face challenges such as high manufacturing complexity, increased cost, and substrate distortion due to high-temperature processing, while amorphous silicon-based devices have low mobility and high power consumption, and are prone to substrate damage during film formation.
Innovation Solution
The use of oxide semiconductors like zinc oxide (ZnO) with lamp rapid thermal annealing (LRTA) to promote crystallization in the channel region of TFTs, allowing for the production of semiconductor devices with improved mobility and reduced manufacturing costs, while avoiding substrate distortion and damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If crystalline silicon is used for TFT semiconductor film, then mobility is improved (higher by two digits or more), but manufacturing complexity increases and cost increases due to crystallization steps
Solution Approach 1:
The patent changes the material parameter from crystalline silicon to oxide semiconductor (such as In-Ga-Zn-O), which inherently provides high mobility without requiring crystallization steps. This material substitution resolves the contradiction by achieving high-speed operation through different physical mechanisms while simplifying the manufacturing process.
2Speed
If crystalline silicon is used for TFT semiconductor film, then mobility is improved, but manufacturing cost increases due to additional crystallization steps
Solution Approach 1:
The patent changes the material parameter from crystalline silicon to oxide semiconductor (such as In-Ga-Zn-O), which inherently provides high mobility without requiring crystallization steps. This material substitution resolves the contradiction by achieving high-speed operation through different physical mechanisms while simplifying the manufacturing process.
3Reliability
If high temperature heating (550°C or higher) is applied for crystallization, then crystalline silicon TFT performance is improved, but substrate distortion occurs and resin substrates cannot be used
Solution Approach 1:
The patent changes the material parameter from crystalline silicon to oxide semiconductor (such as In-Ga-Zn-O), which can be processed at lower temperatures (below 450°C) while maintaining high mobility. This enables the use of resin substrates and prevents substrate distortion while achieving reliable TFT performance.
4Ease of manufacture
If amorphous silicon is used for TFT semiconductor film, then manufacturing cost is reduced and resin substrates can be used, but mobility is low (0.2 to 1.0 cm2/V·s) and power consumption is high
Solution Approach 1:
The patent changes the material parameter from amorphous silicon to oxide semiconductor (such as In-Ga-Zn-O), which provides high mobility (comparable to or exceeding crystalline silicon) while maintaining compatibility with low-cost manufacturing processes and resin substrates. This resolves the contradiction by achieving high performance through different material physics.
5Ease of manufacture
If plasma CVD method is used to form amorphous silicon film, then film formation is achieved, but substrate damage occurs due to high vacuum heating
Solution Approach 1:
The patent changes the material parameter from amorphous silicon to oxide semiconductor (such as In-Ga-Zn-O), which can be deposited using sputtering methods at lower temperatures and with less substrate damage. The oxide semiconductor films can be formed at temperatures below 450°C, preventing substrate damage while achieving high-quality films.
6Ease of manufacture
If sputtering method is used to form amorphous silicon film, then film formation is achieved, but insulating film forms on surface when exposed to atmospheric air
Solution Approach 1:
The patent changes the material parameter from amorphous silicon to oxide semiconductor (such as In-Ga-Zn-O). Since oxide semiconductors already contain oxygen in their crystal structure, they do not form additional insulating oxide films when exposed to atmospheric air. This eliminates the quality degradation issue while maintaining the advantages of sputtering deposition.
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 enables the production of semiconductor devices with enhanced mobility and cost-effectiveness, while maintaining substrate integrity and reducing power consumption, and allows for the use of low-temperature processing, making it suitable for large-area displays.
Implementation Method 1
by heating a gate electrode that is near the compound semiconductor by lamp rapid thermal annealing (LRTA; also simply called lamp heating), crystallization of the compound semiconductor is selectively promoted
Implementation Method 2
crystallization of the compound semiconductor is selectively promoted
Implementation Method 3
when a substrate is heated to a high temperature during a heat treatment step, a size of the substrate becomes distorted due to warping and shrinking
Data Source
AI summary
An object is to provide a semiconductor device of which a manufacturing process is not complicated and by which cost can be suppressed, by forming a thin film transistor using an oxide semiconductor film typified by zinc oxide, and a manufacturing method thereof. For the semiconductor device, a gate electrode is formed over a substrate; a gate insulating film is formed covering the gate electrode; an oxide semiconductor film is formed over the gate insulating film; and a first conductive film and a second conductive film are formed over the oxide semiconductor film. The oxide semiconductor film has at least a crystallized region in a channel region.