Array Substrate Oxygen Content Control for TFT Reliability
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Solution Overview
Problem
Conventional array substrates face reliability issues due to negative shift in threshold voltage of thin film transistors in the display area under externally applied voltages, affecting their performance over time.
Innovation Solution
The method involves forming thin film transistors in the display area with a higher oxygen content in their active layers than those in the peripheral area, using plasma bombardment with oxygen-containing plasmas to increase oxygen content, while maintaining the same oxygen content in channel, source, and drain regions, and using a photoresist layer to protect the peripheral area transistors from plasma treatment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a single patterning process is used to form both display area and peripheral area thin film transistors, then manufacturing efficiency and cost are improved, but the ability to control different oxygen content in different regions deteriorates
Solution Approach 1:
The patent implements local quality control by applying oxygen plasma treatment selectively to the display area after single patterning. The photoresist layer protects peripheral area transistors during this treatment, ensuring that only display area transistors receive the oxygen enrichment. This maintains manufacturing efficiency while achieving precise regional oxygen content differentiation.
Solution Approach 2:
The patent uses preliminary photoresist coating on peripheral area transistors before oxygen plasma treatment. This preliminary protective action prevents oxygen from penetrating into peripheral transistors, enabling subsequent selective oxygen enrichment of display area transistors without compromising peripheral transistor performance.
2Reliability
If oxygen plasma treatment is applied to all thin film transistors to improve reliability, then the negative bias voltage stress tolerance is improved, but the positive bias voltage stress tolerance and overall device complexity increase
Solution Approach 1:
The patent applies oxygen plasma treatment locally only to the display area rather than uniformly to all transistors. The photoresist layer serves as a spatial mask, allowing oxygen enrichment in display area transistors while protecting peripheral area transistors. This localized approach improves negative bias tolerance where needed without unnecessarily complicating the overall device structure or processing.
Solution Approach 2:
The patent introduces a photoresist layer as an intermediary protective element during oxygen plasma treatment. This intermediary material selectively blocks oxygen from reaching peripheral area transistors while allowing treatment of display area transistors. The photoresist acts as a temporary mediator that enables precise spatial control of oxygen content without requiring complex device redesign.
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 enhances negative bias voltage stress tolerance in the display area while maintaining positive bias voltage stress tolerance in the peripheral area, ensuring the reliability of thin film transistors in both regions.
Implementation Method 1
plasma bombardment with oxygen-containing plasmas to increase oxygen content
Data Source
AI summary
The present application discloses an array substrate having a display area and a peripheral area. The array substrate includes a plurality of first thin film transistors respectively in a plurality of subpixels in the display area; and a plurality of second thin film transistors in the peripheral area, an oxygen content in active layers of the plurality of first thin film transistors being higher than that in active layers of the plurality of second thin film transistors.