Oxide TFT Light Shielding Structure for Low-Gray Leakage Control
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Solution Overview
Problem
Current display devices face challenges in achieving low-grayscale expression and blocking leakage current, particularly in organic light emitting display devices, where the oxide semiconductor pattern's high s-factor is necessary but often results in fluctuation issues and reliability problems due to hydrogen particle penetration and threshold voltage control.
Innovation Solution
The implementation of a display device structure that includes an oxide semiconductor pattern with a light shielding pattern doped with P-type impurity ions and a dual gate configuration, which increases the threshold voltage and reduces leakage current, allowing for precise grayscale expression and improved reliability by adjusting parasitic capacitances and using specific buffer layers to prevent hydrogen particle degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an oxide semiconductor pattern with high s-factor is used to achieve low-grayscale expression, then grayscale precision at low gray levels is improved, but threshold voltage control and reliability deteriorate due to hydrogen particle penetration
Solution Approach 1:
A light shielding pattern serving as a hydrogen barrier layer is introduced between the oxide semiconductor pattern and the buffer layer. This intermediary layer blocks hydrogen particles from penetrating into the oxide semiconductor, thereby preventing threshold voltage shifts while preserving the high s-factor characteristics of the oxide semiconductor for precise low-grayscale expression.
Solution Approach 2:
The harmful function of the buffer layer (hydrogen particle generation and penetration) is separated from the oxide semiconductor pattern by removing or modifying the buffer layer in the region underlying the oxide semiconductor pattern. This extraction of the harmful element prevents hydrogen contamination while maintaining the beneficial electrical characteristics of the oxide semiconductor.
2Reliability
If a light shielding pattern doped with P-type impurity ions is introduced to block leakage current, then off-state leakage current blocking is improved, but device complexity increases
Solution Approach 1:
The light shielding pattern is designed to perform multiple functions simultaneously: it serves as a hydrogen barrier layer to prevent threshold voltage shifts, as a leakage current blocking layer through P-type doping, and as a light shielding structure. This multi-functionality reduces overall device complexity by consolidating multiple protective functions into a single integrated component.
Solution Approach 2:
The light shielding pattern merges the functions of the hydrogen barrier layer and the leakage current blocking layer into a single structure. By combining these functions, the patent reduces the number of separate layers and simplifies the transistor structure while achieving both protective functions effectively.
3Reliability
If the threshold voltage is increased to block leakage current, then off-state current control is improved, but power consumption increases
Solution Approach 1:
P-type impurity ions are doped specifically in the light shielding pattern and source/drain regions rather than uniformly throughout the entire transistor structure. This localized doping approach increases threshold voltage control and blocks leakage current only where necessary, minimizing the impact on overall power consumption while maintaining low-grayscale expression capabilities.
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 configuration enhances the display device's ability to achieve free grayscale expression at low gray levels while maintaining high threshold voltage, reducing power consumption, and improving reliability by effectively blocking leakage current and managing hydrogen particle effects.
Implementation Method 1
a light shielding pattern disposed between the substrate and the second transistor while overlapping with the second oxide semiconductor pattern and including a metal layer or P-type impurity ions
Implementation Method 2
a light shielding pattern disposed between the substrate and the first transistor while including a metal layer or P-type impurity ions
Data Source
AI summary
The disclosure relates to a display device including an oxide semiconductor pattern. The disclosure provides a driving thin film transistor and a switching thin film transistor using an oxide semiconductor pattern as an active layer. Each of the driving thin film transistor and the switching thin film transistor includes a light shielding pattern. The light shielding pattern includes a semiconductor material layer doped with P-type impurity ions. By virtue of the light shielding pattern including the semiconductor material layer, each of the driving thin film transistor and the switching thin film transistor exhibits an increase in threshold voltage and, as such, freedom of circuit design is secured.