Nb-Doped TiOx Amorphous Oxide Semiconductor for High Mobility TFTs
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Solution Overview
Problem
Current thin film transistors face limitations in achieving high performance due to low charge mobility in amorphous silicon and high cost, low uniformity, and crystallization issues with polysilicon-based oxide semiconductors, which hinder the manufacturing of large-sized thin film transistor array panels.
Innovation Solution
A thin film transistor using an oxide semiconductor layer made of titanium oxide (TiOx) doped with niobium (Nb), maintained in an amorphous state through heat treatment between 350°C to 550°C, with niobium doping ranging from 1 to 17 atomic percent, integrated with a gate electrode, source, and drain electrodes, and an etch stopper to enhance semiconductor characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If amorphous silicon is used as the semiconductor material, then the manufacturing cost is low and uniformity is maintained, but the charge mobility is low which limits thin film transistor performance
Solution Approach 1:
The patent changes the material composition parameters by doping niobium into the oxide semiconductor at controlled concentrations (1-17 atomic percent), which fundamentally alters the electrical properties and achieves high charge mobility while maintaining amorphous structure
Solution Approach 2:
The patent creates a composite oxide semiconductor material combining titanium oxide with niobium dopant, achieving synergistic effects that provide both high charge mobility and stability while maintaining amorphous characteristics suitable for large-area manufacturing
2Reliability
If polysilicon is used as the semiconductor material, then the charge mobility is high and thin film transistor performance is improved, but the manufacturing cost increases and uniformity decreases
Solution Approach 1:
The patent modifies the semiconductor material composition by introducing niobium-doped oxide semiconductor, achieving polysilicon-level charge mobility while maintaining the manufacturing advantages of amorphous materials including uniformity and low cost
Solution Approach 2:
The patent employs an amorphous oxide semiconductor that can be manufactured at lower costs compared to crystalline polysilicon, achieving high performance without requiring expensive crystallization processes while maintaining stability through proper doping
3Reliability
If polysilicon-based oxide semiconductor is used, then the charge mobility is high, but crystallization occurs which limits large-sized thin film transistor array panel manufacturing
Solution Approach 1:
The patent optimizes the doping concentration parameters (1-17 atomic percent niobium) to achieve a balance where high charge mobility is obtained while the amorphous structure remains stable and resistant to unwanted crystallization
Solution Approach 2:
The patent uses niobium as an intermediary dopant that modifies the oxide semiconductor structure to prevent crystallization while enhancing charge mobility, acting as a stabilizing agent that maintains the amorphous state
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 high charge mobility and ON/OFF current ratio comparable to polysilicon, while maintaining low cost and high uniformity, suitable for large-area displays, by suppressing crystallization and maintaining the amorphous state of the oxide semiconductor layer.
Implementation Method 1
The oxide semiconductor layer includes titanium oxide (TiOx) doped with niobium (Nb). An amount of niobium doped to the titanium oxide may be in a range from equal to or more than about 1 atomic percent (at. %) to equal to or less than about 17 at. %.
Implementation Method 2
The oxide semiconductor layer may be formed by a heat treatment, and the oxide semiconductor layer may be maintained in an amorphous state after the heat treatment. The oxide semiconductor layer may be heat-treated at a temperature in a range from equal to or more than about 350 degrees Celsius (° C.) to equal to or less than about 550° C.
Data Source
AI summary
A thin film transistor includes: a gate electrode on a substrate; a source electrode; a drain electrode positioned in a same layer as the source electrode and facing the source electrode; an oxide semiconductor layer positioned between the gate electrode and the source electrode or drain electrode; and a gate insulating layer positioned between the gate electrode and the source electrode or drain electrode. The oxide semiconductor layer includes titanium oxide (TiOx) doped with niobium (Nb).