TFT Substrate Channel Shielding for Threshold Voltage Stability
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Solution Overview
Problem
Existing thin film transistor substrates face challenges in preventing exposure to hydrogen and light, which can lead to shifts in threshold voltage and reduced reliability, especially when the channel area has a large width.
Innovation Solution
Incorporating an active hole in the thin film transistor substrate and a conductive material layer overlapping the channel area to prevent exposure to hydrogen and light, thereby maintaining the stability of the threshold voltage and enhancing reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the channel area has a large width to improve current driving ability, then the transistor performance is improved, but the threshold voltage shifts in negative direction due to increased exposure to hydrogen and light
Solution Approach 1:
A conductive material layer is introduced as an intermediary between the active layer and the environment. This layer overlaps the channel area and acts as a barrier to prevent hydrogen and light from reaching the active layer, thereby preventing threshold voltage shifts while maintaining the large channel width for current driving ability.
Solution Approach 2:
The protection mechanism is added in a vertical dimension by stacking the conductive material layer above the channel area. This allows the channel to maintain its horizontal width for current driving while the vertical stacking provides protection against environmental factors causing threshold voltage shifts.
2Power
If the channel area has a large width to improve current driving ability, then the transistor performance is improved, but the exposure to hydrogen and light increases leading to reduced reliability
Solution Approach 1:
The conductive material layer serves as a protective intermediary that blocks hydrogen and light from reaching the active layer. This layer is positioned to overlap the channel area, providing shielding against harmful environmental factors while allowing the channel to maintain its functional width.
3Reliability
If a conductive material layer is added to prevent hydrogen and light exposure, then reliability is improved, but device complexity increases
Solution Approach 1:
The conductive material layer performs multiple functions simultaneously: it serves as an electrode for electrical connection and as a protective barrier against hydrogen and light. This multi-functionality reduces the need for separate protective structures, thereby limiting the increase in device complexity while improving reliability.
4Reliability
If a conductive material layer overlapping the channel area is added to prevent hydrogen and light exposure, then reliability is improved, but manufacturing complexity increases
Solution Approach 1:
The conductive material layer is merged with the electrode structure of the transistor. By combining the protective function with the existing electrical connection requirement, the manufacturing process does not need entirely separate steps for protection, thereby limiting the increase in manufacturing complexity while achieving improved reliability.
Data Source
AI summary
A thin film transistor substrate includes a thin film transistor, on a substrate, including an active layer; a conductive material layer; and a gate electrode spaced apart and partially overlapping the active layer. The active layer includes a channel area partially overlapping the gate electrode, and a source area and a drain area connected to respective sides of the channel area. The conductive material layer includes a first and second conductive material layer respectively on the source drain areas. The first conductive material layer overlaps at least a portion of the channel area. The active layer includes an active hole in which the active layer is absent within an area defined by the active layer, and, in a plan view, the active hole extends from the channel area to the drain area.