Thin Film Transistor Buffer Layer Oxygen Gradient for Leakage Current
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Solution Overview
Problem
Thin film transistors in display devices, particularly those using oxide semiconductor materials, face challenges with leakage currents due to negative threshold voltages, which affect the reliability and efficiency of gate pulse supply in shift registers, leading to issues with electrical reliability and display performance.
Innovation Solution
A thin film transistor substrate design incorporating a multi-layered buffer layer and gate insulating film structure with varying oxygen concentrations and bond types, creating a dipole moment that shifts the threshold voltage to a positive direction, thereby preventing leakage currents without the need for additional transistors, reducing the complexity and area of shift registers and improving display efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If oxide semiconductor is used for semiconductor layer, then low temperature manufacturing is enabled, but negative threshold voltage causes leakage current
Solution Approach 1:
The patent changes the oxygen concentration parameter in the buffer layer to resolve the contradiction. By controlling the oxygen concentration to be 1×10^18 to 1×10^20 atoms/cm³, the threshold voltage is adjusted from negative to positive, eliminating leakage current while maintaining low-temperature manufacturing capability
Solution Approach 2:
The patent employs a composite structure with multiple buffer layers having different oxygen concentrations. The first buffer layer (higher oxygen concentration) and second buffer layer (lower oxygen concentration) work together to achieve both low-temperature processing and positive threshold voltage, preventing leakage current
2Reliability
If additional transistors are added to prevent leakage current, then reliability improves, but device complexity and area increase
Solution Approach 1:
The patent extracts the leakage current prevention function from the transistor circuit level and relocates it to the material level by controlling oxygen concentration in the buffer layer. This eliminates the need for additional transistors while maintaining reliability
Solution Approach 2:
The buffer layer with controlled oxygen concentration acts as an intermediary that prevents leakage current without requiring additional transistors. The dipole moment created by the oxygen concentration gradient in the buffer layer serves as the mechanism to achieve reliability improvement while avoiding increased device complexity
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 effectively prevents leakage currents, enhancing the reliability and efficiency of thin film transistors, simplifying the shift register structure, and improving the overall performance of display devices by eliminating the need for additional transistors and reducing the area required for the gate driver.
Implementation Method 1
A dipole moment is formed between the first buffer layer and the second buffer layer
Data Source
AI summary
A thin film transistor substrate can include a buffer layer on a base substrate and having a first buffer layer and a second buffer layer; a semiconductor layer disposed on the buffer layer; a gate insulating film on the semiconductor layer; and a gate electrode spaced apart from the semiconductor layer, at least a part of the gate electrode overlapping with the semiconductor layer. The base substrate, the first buffer layer, the second buffer layer, the semiconductor layer, the gate insulating film and the gate electrode are sequentially stacked, and a surface oxygen concentration of the first buffer layer is higher than a surface oxygen concentration of the second buffer layer.