Gate Electrode Light Shielding for TFT Leakage Current
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Solution Overview
Problem
In liquid crystal devices, light leakage current occurs due to oblique light entry into the semiconductor layer of TFTs, leading to display defects like flicker and pixel chrominance non-uniformity, which degrade image quality.
Innovation Solution
An electro-optical device substrate with a specific gate electrode structure, including a body portion, first elongated portions, and second elongated portions, is used to effectively block light from entering the semiconductor layer, particularly at the second junction region, by forming a longitudinal groove in the insulating film and extending the elongated portions to enhance light shielding properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a light shielding film is installed to block light from entering the TFT, then light leakage current is reduced, but the light shielding film is spaced apart from the semiconductor layer through insulating films, allowing oblique light to still reach the semiconductor layer and cause light leakage current
Solution Approach 1:
The gate electrode is extended in the vertical dimension (thickness direction of the insulating film) to reach the semiconductor layer, creating a three-dimensional light shielding structure that blocks light from multiple angles and prevents oblique light from reaching the semiconductor layer
Solution Approach 2:
The gate electrode structure is designed to be nested within the insulating film layer, with the gate electrode extending through the insulating film to directly contact or adjacent to the semiconductor layer, creating a compact integrated light shielding structure
2Object-affected harmful factors
If the gate electrode is extended to adjoin the second junction region to improve light shielding, then light leakage current is further reduced, but the device structure becomes more complex
Solution Approach 1:
The gate electrode serves multiple functions: it acts as the control electrode for the TFT, provides light shielding for the channel region, and extends to adjoin the second junction region to provide additional light shielding, eliminating the need for separate light shielding structures
Solution Approach 2:
The light shielding function is merged with the gate electrode structure, combining the control function and light shielding function into a single integrated component rather than using separate dedicated light shielding films
Data Source
AI summary
An electro-optical device substrate includes a substrate, a plurality of data lines, a plurality of scanning lines, pixel electrodes, and transistors. The plurality of data lines and the plurality of scanning lines intersect with each other in a display area formed on the substrate. The pixel electrodes are provided at positions corresponding to intersections of the plurality of data lines and the plurality of scanning lines. Each of the transistors includes a semiconductor layer and a gate electrode. The semiconductor layer has a channel region, a data line side source/drain region, a pixel electrode side source/drain region, a first junction region, and a second junction region. The channel region has a channel length along a first direction in the display area. The data line side source/drain region is electrically connected to a corresponding data line. The pixel electrode side source/drain region is electrically connected to a corresponding pixel electrode.