Oxide TFT Carrier Gradient for Short-Channel Stability
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Solution Overview
Problem
Conventional thin film transistors with oxide semiconductors face challenges in maintaining stable electrical characteristics as the channel length is reduced, leading to shifts in threshold voltage and increased variability.
Innovation Solution
The thin film transistor incorporates an oxide semiconductor layer with a polycrystalline structure, featuring a carrier concentration gradient that suppresses hydrogen diffusion, thereby maintaining stable electrical characteristics even at shorter channel lengths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the channel length is reduced to improve integration density and device scaling, then productivity and device miniaturization are improved, but electrical characteristic stability deteriorates due to threshold voltage shifts and increased variability
Solution Approach 1:
The oxide semiconductor layer is designed with spatially varying carrier concentrations: a first region with lower carrier concentration overlapping the gate electrode, a second region with higher carrier concentration not overlapping the gate electrode, and a third region with gradient carrier concentration between them. This local quality differentiation suppresses hydrogen diffusion and maintains electrical stability even at reduced channel lengths, resolving the contradiction between device scaling and reliability.
Solution Approach 2:
The invention changes the carrier concentration parameter within the oxide semiconductor layer by controlling oxygen partial pressure during formation. By creating regions with different carrier concentrations (first region: lower, second region: higher, third region: gradient), the device achieves both short channel length for scaling and stable electrical characteristics through suppressed hydrogen diffusion.
2Productivity
If the channel length is reduced to improve device performance and integration, then productivity is improved, but manufacturing precision deteriorates due to difficulty in controlling electrical characteristics
Solution Approach 1:
By creating distinct regions with different carrier concentrations within the oxide semiconductor layer, the invention enables precise control of electrical characteristics. The first region (lower carrier concentration) provides stable threshold voltage, while the second region (higher carrier concentration) ensures good contact, and the third region (gradient) transitions between them, achieving manufacturing precision even at reduced channel lengths.
Solution Approach 2:
The carrier concentration gradient is built into the oxide semiconductor layer during its formation process by controlling oxygen partial pressure. This preliminary structuring of the semiconductor layer prevents subsequent electrical characteristic drift, enabling precise control without requiring additional post-processing steps.
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
This design allows for a higher degree of freedom in channel length design, resulting in improved stability and performance of the thin film transistor, particularly at shorter channel lengths.
Implementation Method 1
The thin film transistor incorporates an oxide semiconductor layer with a polycrystalline structure, featuring a carrier concentration gradient that suppresses hydrogen diffusion
Data Source
AI summary
A thin film transistor includes an oxide semiconductor layer having a polycrystalline structure over a substrate, a gate electrode over the oxide semiconductor layer, and a gate insulating layer between the oxide semiconductor layer and the gate electrode. The oxide semiconductor layer includes a first region having a first carrier concentration and overlapping the gate electrode, a second region having a second carrier concentration and not overlapping the gate electrode, and a third region between the first region and the second region and overlapping the gate electrode. The second carrier concentration is larger than the first carrier concentration. A carrier concentration of the third region decreases from the second region to the first region in a channel length direction. A length of the third region is greater than or equal to 0.00 μm and less than or equal to 0.60 μm in the channel length direction.