Light-Shielding Film Positioning in Polysilicon TFTs
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In thin-film transistors used in display devices, a leakage current is caused by light irradiation of the semiconductor layer, leading to operation errors and unstable pixel potentials due to parasitic capacitance between the light-shielding film and the semiconductor layer, which affects display quality.
Innovation Solution
A light-shielding film is strategically positioned to shield the semiconductor layer from light, particularly at areas where optical leakage is pronounced, such as the boundary between the channel and impurity areas on the pixel electrode side, while avoiding opposition to the source line and gate line to minimize parasitic capacitance and capacitive coupling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a light-shielding film is provided to shield the semiconductor layer from light, then optical leakage is suppressed, but parasitic capacitance increases
Solution Approach 1:
The light-shielding film is selectively positioned to cover only specific areas of the semiconductor layer where optical leakage is most pronounced (channel area and boundary areas), rather than covering the entire semiconductor layer. This localized approach maintains effective light shielding while minimizing the overlapping area and thus reducing parasitic capacitance between the light-shielding film and the semiconductor layer.
2Object-affected harmful factors
If the light-shielding film is positioned to cover the entire semiconductor layer, then light shielding is maximized, but pixel potential stability deteriorates
Solution Approach 1:
The light-shielding film is strategically positioned to cover only the channel area and boundary areas of the semiconductor layer, excluding the impurity areas. This selective coverage provides sufficient light shielding for the critical regions while minimizing capacitive coupling with the source line and pixel electrode, thereby maintaining pixel potential stability.
Solution Approach 2:
The semiconductor layer is functionally segmented into different areas (channel area, impurity areas, boundary areas), and the light-shielding film is applied only to specific segments where it is most needed. This segmentation allows differential treatment of different regions, providing light shielding where necessary while avoiding unnecessary capacitance in other regions.
3Object-affected harmful factors
If the light-shielding film overlaps the source line, then light shielding is improved, but capacitive coupling with the source line increases
Solution Approach 1:
The light-shielding film is extracted or removed from overlapping with the source line area. By positioning the light-shielding film to cover only the channel and boundary areas while excluding the impurity areas near the source line connection, the design eliminates unnecessary capacitive coupling between the light-shielding film and the source line, while still providing adequate light shielding for the active channel region.
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 effectively suppresses optical leakage and stabilizes pixel potentials, improving display quality by reducing unwanted capacitance and light exposure, thereby enhancing the reliability of the display device.
Implementation Method 1
a light-shielding film located between the insulating substrate and the semiconductor layer, disposed at a position displaced from a position opposed to the source line, and opposed to an area including a boundary between the channel area and the second impurity area
Implementation Method 2
A parasitic capacitance is produced between the light-shielding film and the semiconductor layer
Data Source
AI summary
A display device includes an insulating substrate, a semiconductor layer formed of polycrystalline silicon, including a first impurity area, a second impurity area, and a channel area, an insulating film which covers the semiconductor layer, a gate electrode formed on the insulating film and opposed to the channel area, a source line electrically connected to the first impurity area, an electrode electrically connected to the second impurity area, and a light-shielding film located between the insulating substrate and the semiconductor layer, disposed at a position displaced from a position opposed to the source line, and opposed to an area including a boundary between the channel area and the second impurity area.