Oxide Semiconductor Double Gate Transistor Leakage Control
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Solution Overview
Problem
Current TFT technologies face challenges in achieving high mobility and cost-effectiveness for large-screen, high-definition displays, with amorphous silicon TFTs limited by low mobility and poly silicon TFTs being costly and difficult to manufacture on large substrates.
Innovation Solution
The development of an oxide semiconductor thin film transistor (TFT) with a channel layer using oxide semiconductor materials like Zinc Oxide, Tin Oxide, and Ga—In—Zn Oxide, featuring a double gate structure with different insulating layers made of silicon nitride and silicon oxide, which enhances mobility and reduces manufacturing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If amorphous silicon TFTs are used, then manufacturing cost is reduced and large-scale production is enabled, but mobility is limited to below 0.5 cm2/Vs
Solution Approach 1:
The patent changes the material parameter from conventional amorphous silicon to oxide semiconductor materials (such as IGZO - indium gallium zinc oxide), which fundamentally alters the electrical properties to achieve high mobility while maintaining the amorphous phase for low-cost manufacturing
Solution Approach 2:
The patent employs composite material structures including oxide semiconductor channel layers combined with specific gate insulating layer compositions (such as IGZO with aluminum oxide or silicon oxide), creating a composite system that achieves both high mobility and manufacturing feasibility
2Reliability
If poly silicon TFTs are used, then mobility increases to several tens to hundreds of cm2/Vs, but manufacturing complexity and cost increase significantly
Solution Approach 1:
The patent changes the crystalline state parameter from polycrystalline to amorphous phase of oxide semiconductors, achieving high mobility without requiring the complex laser annealing or solid-phase crystallization processes needed for poly-Si
Solution Approach 2:
The patent replaces the thermal processing mechanisms (laser annealing, solid-phase crystallization) required for poly-Si with low-temperature deposition and simple annealing processes for oxide semiconductors, substituting complex thermal-mechanical systems with simpler chemical-vapor-deposition-based approaches
3Manufacturing precision
If poly silicon TFTs are used, then high definition display performance is achieved, but application to large-screen TVs with substrates of 1 meter or more is difficult due to equipment limits and uniformity issues
Solution Approach 1:
The patent changes the material phase from polycrystalline to amorphous oxide semiconductor, which can be deposited uniformly over large areas using sputtering or CVD techniques without requiring large-area laser annealing equipment
Solution Approach 2:
The patent transitions from requiring complex in-plane uniformity control in poly-Si to achieving uniformity through vertical layer control in oxide semiconductors, where the amorphous phase allows consistent properties across the entire substrate area
4Ease of manufacture
If a single gate insulating layer structure is used, then manufacturing is simpler, but mobility enhancement and leakage current control are insufficient
Solution Approach 1:
The patent segments the gate insulating structure into multiple functional layers (first gate insulating layer and second gate insulating layer with different materials), where each layer serves a specific function in controlling the channel and reducing leakage
Solution Approach 2:
The patent applies different material compositions to different regions of the gate insulating structure, with the first gate insulating layer having different properties than the second gate insulating layer, optimizing each region for its specific function in mobility enhancement and leakage control
Data Source
AI summary
An oxide semiconductor thin film transistor (TFT) and a method of manufacturing the oxide semiconductor TFT. The oxide semiconductor TFT includes a first gate insulating layer arranged between an oxide semiconductor channel layer and a first gate and a second gate insulating layer arranged between the channel layer and a second gate. The first and second gate insulating layers are made out of different materials and have different thicknesses. Preferably, the second gate insulating layer is silicon oxide and is thinner than the first gate insulating layer which is preferably silicon nitride. Oxide semiconductor refers to an oxide material such as Zinc Oxide, Tin Oxide, Ga—In—Zn Oxide, In—Zn Oxide, In—Sn Oxide, and one of Zinc Oxide, Tin Oxide, Ga—In—Zn Oxide, In—Zn Oxide and In—Sn Oxide.