Amorphous Oxide Semiconductor Material for Stable TFT Operation
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Solution Overview
Problem
Amorphous IGZO semiconductor materials used in TFTs for display devices exhibit significant changes in properties when irradiated with visible light in the short-wavelength region (400-420 nm), affecting stable operation, and existing solutions do not adequately address improving light irradiation properties or photostability.
Innovation Solution
An amorphous oxide semiconductor material with a specific composition ratio of In:Ga:Zn, defined by a+b=2 and b<2, c-5b+8>1, and an optical band gap of 3.79 eV or greater, is developed to reduce light absorption in the visible light short-wavelength region, enhancing photostability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If amorphous IGZO is used as the active layer material, then the TFT can be formed at low temperature and exhibits excellent semiconductor characteristics, but the TFT properties greatly change when irradiated with visible light in the short-wavelength region (400-420 nm)
Solution Approach 1:
The patent changes the compositional parameters of the IGZO material by introducing Ga element and controlling the In:Ga:Zn atomic ratio within specific ranges (0.2≤In/(In+Zn)≤0.6 and 0.2≤Zn/(In+Zn+Ga)≤0.8). This parameter optimization modifies the material's optical properties to achieve an optical band gap of 3.7 eV or more, thereby reducing light absorption in the 400-420 nm region and improving photostability while maintaining low-temperature formability
Solution Approach 2:
The patent creates a composite oxide semiconductor material by combining multiple elements (In, Ga, Zn, and oxygen) in specific proportions. The synergistic effect of these elements produces a material with enhanced optical band gap (3.7 eV or more) while maintaining the amorphous structure and low-temperature processing characteristics of IGZO, effectively resolving the contradiction between ease of manufacture and photostability
2Reliability
If the optical band gap is increased to 3.79 eV or greater to reduce light absorption, then photostability is improved, but the composition ratio constraints become more stringent
Solution Approach 1:
The patent establishes specific parameter ranges for composition ratios (0.2≤In/(In+Zn)≤0.6 and 0.2≤Zn/(In+Zn+Ga)≤0.8) that guarantee the optical band gap reaches 3.7 eV or more. These parameter specifications provide clear manufacturing guidelines that balance the need for high photostability with practical compositional control, avoiding overly stringent requirements while achieving the desired optical properties
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 material effectively reduces light absorption in the 400-420 nm range, improving the photostability and operational stability of TFTs when used in display devices, allowing them to function reliably without requiring light blocking mechanisms.
Implementation Method 1
when a TFT whose gate electrode comprises n-type Si, whose gate insulating film comprises a thermally-oxidized film, whose source and drain electrodes comprise Al and whose active layer comprises amorphous IGZO (In:Ga:Zn=1:1:1) has been irradiated with monochromatic light in a dark place... when the TFT is irradiated with λ≦420 nm monochromatic light, the TFT properties greatly change
Data Source
AI summary
There is provided an amorphous oxide semiconductor material including an amorphous oxide semiconductor including In, Ga and Zn, wherein when In:Ga:Zn=a:b:c denotes an element composition ratio of the oxide semiconductor, the element composition ratio is defined by the range of a+b=2 and b<2 and c<4b−3.2 and c>−5b+8 and 1≦c≦2.