Oxide Semiconductor TFT With Selective Crystallization
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Solution Overview
Problem
Amorphous silicon-based thin film transistors (TFTs) used in liquid crystal displays have low charge carrier mobility, limiting the operating speed of these displays, and existing materials like Ga—In—Zn—O offer higher mobility but require improved manufacturing methods for stable contact characteristics and low off-current operation.
Innovation Solution
A TFT with a channel layer formed from an oxide semiconductor, specifically (In2O3). (Ga2O3). (ZnO) doped with titanium or lanthanum, where at least a portion of the channel layer contacting the source and drain is crystallized through metal injection and heat-treatment, enhancing charge carrier mobility and reducing off-current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If amorphous Si is used for forming channel layers of TFTs, then process temperature and substrate compatibility are improved, but charge carrier mobility deteriorates (0.5 cm2/Vs)
Solution Approach 1:
The patent changes the material parameter from amorphous Si to oxide semiconductor (Ga-In-Zn-O), which allows for higher charge carrier mobility while maintaining compatibility with low-temperature processing and flexible substrates. The oxide semiconductor material inherently provides better electrical properties without requiring high-temperature crystallization processes.
Solution Approach 2:
The patent uses a composite structure combining oxide semiconductor channel layer with selectively crystallized regions. The channel layer is formed of Ga-In-Zn-O with specific atomic ratios, creating a material composition that optimizes both mobility and processability. The selective crystallization introduces local structural variation to enhance contact characteristics.
2Reliability
If selective crystallization is applied to channel layer, then contact characteristics are improved, but manufacturing complexity increases
Solution Approach 1:
The patent performs selective crystallization treatment after forming the complete TFT structure including source and drain electrodes. This preliminary action approach allows the crystallization process to be applied to the already-formed device, targeting specific contact regions without requiring complex masking or positioning steps during earlier manufacturing stages. The treatment simplifies the overall process flow while achieving the desired contact improvement.
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
The solution achieves stable contact characteristics and low off-current operation, increasing charge carrier mobility and minimizing the deterioration of TFT characteristics due to grain boundaries, while allowing for selective crystallization at lower temperatures.
Implementation Method 1
ion-injecting the metal component into the channel layer
Implementation Method 2
crystallizing at least a portion of the channel layer contacting the source and the drain by injecting a metal component into the channel layer
Implementation Method 3
heat-treating a resulting structure including the metal layer
Data Source
AI summary
Provided are a thin film transistor (TFT) including a selectively crystallized channel layer, and a method of manufacturing the TFT. The TFT includes a gate, the channel layer, a source, and a drain. The channel layer is formed of an oxide semiconductor, and at least a portion of the channel layer contacting the source and the drain is crystallized. In the method of manufacturing the TFT, the channel layer is formed of an oxide semiconductor, and a metal component is injected into the channel layer so as to crystallize at least a portion of the channel layer contacting the source and the drain. The metal component can be injected into the channel layer by depositing and heat-treating a metal layer or by ion-implantation.