Fluorine-Doped Oxide Semiconductor TFT for Stability
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Solution Overview
Problem
Oxide semiconductor thin film transistors suffer from low stability and electron mobility, leading to unreliable display performance due to oxygen content variations and hydrogen influence, which shifts the threshold voltage and affects long-term driving stability.
Innovation Solution
Incorporating fluorine into the active layer, gate insulating layer, and buffer layer with concentration gradients to enhance stability, prevent negative threshold voltage shifts, and improve electron mobility by forming strong bonds that reduce hydrogen permeation and oxygen vacancies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If oxide semiconductor is used as an active layer, then fabrication cost is reduced due to low temperature processing, but stability and electron mobility are lower than polycrystalline silicon TFTs
Solution Approach 1:
The patent introduces fluorine doping into the oxide semiconductor active layer, changing the chemical composition parameters to improve electron mobility and stability while maintaining low-temperature fabrication capabilities. The fluorine concentration is controlled at specific levels (10^19 to 10^21 atoms/cm³) to optimize performance without sacrificing the low-cost advantage of oxide semiconductor processing.
Solution Approach 2:
The patent creates a composite structure by combining oxide semiconductor with fluorine-doped regions. The fluorine-doped oxide semiconductor layer is formed as a distinct functional region within the active layer, creating a composite material system that leverages both the low-temperature processability of oxide semiconductor and the high mobility/stability benefits of fluorine doping.
2Ease of manufacture
If oxide semiconductor is used as an active layer, then fabrication cost is reduced due to low temperature processing, but electron mobility is lower than polycrystalline silicon TFTs
Solution Approach 1:
The patent modifies the electron mobility parameter by introducing fluorine doping into the oxide semiconductor active layer. The fluorine doping concentration is precisely controlled (10^19 to 10^21 atoms/cm³) to increase carrier concentration and improve electron mobility, enabling oxide semiconductor TFTs to achieve mobility levels comparable to or exceeding conventional polycrystalline silicon TFTs while maintaining low-temperature fabrication advantages.
3Quantity of substance
If oxygen vacancy occurs in oxide semiconductor, then carrier concentration increases, but threshold voltage shifts in negative direction
Solution Approach 1:
The patent converts the harmful effect of oxygen vacancies (which cause threshold voltage instability) into a beneficial effect by introducing fluorine doping. The fluorine atoms fill oxygen vacancy sites and provide controlled carrier generation, transforming the uncontrolled carrier increase from oxygen vacancies into a controlled mechanism that simultaneously increases carrier concentration while stabilizing threshold voltage through the fluorine's electron-withdrawing effect.
Solution Approach 2:
The patent changes the chemical composition parameter by substituting oxygen vacancies with fluorine atoms in the oxide semiconductor lattice. This parameter change allows controlled carrier concentration increase while the fluorine's electronegativity provides a stabilizing effect on threshold voltage, preventing the negative shifts caused by uncontrolled oxygen vacancies.
4Quantity of substance
If hydrogen permeates into oxide semiconductor layer, then threshold voltage changes occur, but uniform driving is compromised
Solution Approach 1:
The patent introduces fluorine as an intermediary element that forms strong bonds with hydrogen, preventing hydrogen from permeating into the oxide semiconductor channel region. The fluorine-doped regions act as a barrier layer that intercepts hydrogen atoms, forming stable fluorine-hydrogen complexes at the interface or within the doped region, thereby protecting the active channel from hydrogen-induced threshold voltage shifts and maintaining uniform device driving characteristics.
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 fluorine-integrated thin film transistor exhibits improved driving stability, increased mobility, and enhanced ON-current performance while minimizing conductorization permeation depth, enabling reliable operation and efficient channel formation.
Implementation Method 1
fluorine (F) is combined with a metal atom to generate a free electron serving as a carrier
Implementation Method 2
MO→MF+e−, where M represents a metal atom
Implementation Method 3
VO2++2e−+F→F−+e−, where VO represents an oxygen vacancy
Implementation Method 4
fluorine (F) strongly combines with hydrogen to prevent hydrogen from being permeated into the channel portion (131)
Data Source
AI summary
A thin film transistor, a fabricating method of the thin film transistor and a display device comprising the thin film transistor are provided, in which the thin film transistor includes an active layer on a substrate, and a gate electrode spaced apart from the active layer and at least partially overlapped with the active layer, wherein the active layer includes fluorine (F) and has a first surface in a direction opposite to the substrate, the active layer has a concentration gradient of fluorine (F) in which a concentration gradient of fluorine (F) along a direction parallel with the first surface is smaller than that of fluorine (F) along a direction perpendicular to the first surface.