ZTO Oxide Semiconductor for Stable TFT Switching
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Solution Overview
Problem
ZTO-based oxide semiconductors for thin-film transistors face challenges in maintaining high ZnO concentration for stable switching properties and stress resistance, particularly after passivation layer formation and under stress tests, due to high carrier concentration and sensitivity to light irradiation and voltage stress.
Innovation Solution
Incorporating at least one element from the X-group (Al, Hf, Ta, Ti, Nb, Mg, Ga, and rare earth elements) into the ZTO-based oxide semiconductor layer to maintain high ZnO concentration, ensuring stable switching properties and stress resistance, with specific atomic ratios for optimal performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the ZnO concentration is increased in ZTO-based oxide semiconductor, then the conductivity of sputtering target improves and film formation becomes easier, but the carrier concentration becomes too high causing the semiconductor layer to become conductive after passivation layer formation, resulting in unstable switching behavior
Solution Approach 1:
The patent changes the chemical composition parameters of the oxide semiconductor by introducing Al, Ga, or In elements to replace部分 Zn atoms. This parameter change allows maintaining high ZnO concentration (70-90 atomic %) while controlling carrier concentration through elemental substitution, thereby stabilizing switching behavior after passivation layer formation.
Solution Approach 2:
The patent creates composite oxide semiconductor materials by combining ZTO with Al, Ga, or In elements to form ZTO-Al, ZTO-Ga, or ZTO-In composite systems. These composite materials exhibit improved electrical properties and stability compared to pure ZTO, enabling stable switching behavior while maintaining ease of film formation.
2Reliability
If the ZnO concentration is decreased in ZTO-based oxide semiconductor, then the carrier concentration is reduced improving switching behavior, but the conductivity of sputtering target is lowered making DC sputtering process difficult to carry out
Solution Approach 1:
The patent modifies the composition parameters by adding Al, Ga, or In elements that have different electrical properties than Zn. These elemental substitutions allow reducing carrier concentration while maintaining or improving target conductivity, thus achieving stable switching behavior without compromising film formation ease.
Solution Approach 2:
The patent uses Al, Ga, or In elements as substitutes for Zn atoms in the ZTO structure. These substitute elements copy the structural role of Zn while providing different electrical characteristics, enabling control of carrier concentration while maintaining the overall crystal structure and film formation properties.
3Reliability
If In is used in In-containing amorphous oxide semiconductors, then high carrier mobility and high optical band gap are achieved, but material cost increases significantly for mass production
Solution Approach 1:
The patent replaces expensive In elements with cheaper Al or Ga elements in the oxide semiconductor composition. This substitution significantly reduces material cost while maintaining the desired electrical properties including carrier mobility, making the technology economically viable for mass production.
Solution Approach 2:
The patent changes the compositional parameters by substituting In atoms with Al or Ga atoms in the oxide semiconductor structure. This parameter change reduces material cost while preserving the high carrier mobility and optical band gap properties needed for display applications.
4Ease of operation
If positive voltage or negative voltage is continuously applied to gate voltage, then the threshold voltage changes considerably, but this voltage stress causes deterioration of TFT properties and lowering of reliability
Solution Approach 1:
The patent incorporates Al, Ga, or In elements in the oxide semiconductor layer before device operation to preemptively stabilize the electrical properties. This beforehand modification cushions against the effects of voltage stress, preventing threshold voltage shifts and maintaining reliable TFT operation under continuous voltage application.
Solution Approach 2:
The patent uses composite oxide semiconductor materials containing Al, Ga, or In elements that exhibit enhanced stability under voltage stress. These composite materials resist threshold voltage shifts better than pure ZTO, ensuring reliable TFT performance during continuous operation with positive or negative gate voltage application.
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 enables stable and excellent TFT characteristics even at high ZnO concentrations, improving reliability in display devices by enhancing stress resistance and maintaining performance after passivation and stress tests.
Implementation Method 1
a sputtering target for forming a film of the oxide
Data Source
AI summary
Disclosed is an oxide for a semiconductor layer of a thin-film transistor, said oxide being excellent in the switching characteristics of a thin-film transistor, specifically enabling favorable characteristics to be stably obtained even in a region of which the ZnO concentration is high and even after forming a passivation layer and after applying stress. The oxide is used in a semiconductor layer of a thin-film transistor, and the aforementioned oxide contains Zn and Sn, and further contains at least one element selected from group X consisting of Al, Hf, Ta, Ti, Nb, Mg, Ga, and the rare-earth elements.