Oxide TFT Barrier Layer Layout for Hydrogen-Induced Threshold Shift
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Solution Overview
Problem
Oxide semiconductor thin film transistors in display devices experience reliability issues due to oxygen defects and increased hydrogen levels, affecting their electrical properties and carrier concentration, leading to deteriorated performance.
Innovation Solution
A display device design incorporating a barrier conductive layer that overlaps the active layer of transistors experiencing negative bias temperature stress to adsorb hydrogen, while not overlapping the active layer of transistors experiencing positive bias temperature stress, thereby controlling hydrogen concentration and reducing defect states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a barrier conductive layer is added to adsorb hydrogen in transistors experiencing negative bias temperature stress, then reliability of these transistors is improved, but device complexity increases
Solution Approach 1:
The barrier conductive layer is selectively formed only in regions where transistors experience negative bias temperature stress (NBTS), while intentionally omitted from regions with positive bias temperature stress (PBTS). This localized approach targets hydrogen adsorption precisely where needed without uniformly increasing device complexity across the entire display panel.
Solution Approach 2:
The display device is divided into different stress regions (NBTS and PBTS areas), and the barrier conductive layer is applied segmentally to only the NBTS regions. This segmentation allows differential treatment of transistors based on their specific stress conditions, improving reliability where necessary while avoiding unnecessary complexity elsewhere.
2Reliability
If oxide semiconductor layer is formed to achieve higher mobility, then transistor performance is improved, but oxygen defects occur leading to electrical property changes
Solution Approach 1:
The barrier conductive layer acts as an intermediary substance between the oxide semiconductor active layer and the external environment. It mediates hydrogen interaction by adsorbing hydrogen atoms, preventing them from entering the oxide semiconductor layer and causing oxygen defects that would degrade electrical properties.
Solution Approach 2:
The barrier conductive layer converts the potentially harmful presence of hydrogen (which would cause oxygen defects and electrical property changes) into a beneficial adsorption process. Hydrogen is redirected to adsorb onto the barrier layer instead of damaging the oxide semiconductor, turning a harmful factor into a controlled interaction.
3Reliability
If hydrogen is introduced to increase carrier concentration, then electrical conductivity is improved, but threshold voltage shifts and reliability deteriorates
Solution Approach 1:
The barrier conductive layer is formed in advance to prevent hydrogen from reaching the oxide semiconductor active layer. By establishing this protective barrier beforehand, the patent prevents the harmful chain reaction where hydrogen would increase carrier concentration excessively, causing threshold voltage shifts and reliability deterioration.
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 approach improves the reliability of both types of transistors by preventing carrier concentration increases and maintaining electrical property stability, effectively addressing the reliability challenges associated with hydrogen and oxygen defects.
Implementation Method 1
a barrier conductive layer disposed so as to overlap a first active layer of a first transistor, the electrical property of which is shifted from an initial value in a decreasing direction
Data Source
AI summary
Disclosed is a display device having improved reliability. The display device includes a first transistor disposed on a substrate, an electrical property of the first transistor being shifted from a first initial value in a decreasing direction; a second transistor disposed on the substrate, an electrical property of the second transistor being shifted from a second initial value in an increasing direction; and a first upper barrier conductive layer disposed so as to overlap a first active layer of the first transistor and not to overlap a second active layer of the second transistor, whereby reliability of each of the first and second transistors is improved.