Thin Film Transistor Light Shielding for Display Quality
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Solution Overview
Problem
Conventional thin film transistors in liquid crystal display devices suffer from light leak currents due to external or display light entering the depletion region, leading to degradation in display quality.
Innovation Solution
The semiconductor device incorporates a source and drain wiring that terminates on the gate wiring, overlapping the semiconductor layer, and a metal layer extending from the contact hole side to shield the semiconductor layer from light, minimizing light leak currents and preventing degradation of display quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the semiconductor layer is exposed to light in the depletion region, then the thin film transistor can be simplified in structure, but light leak current increases and display quality degrades
Solution Approach 1:
The patent introduces an intermediary light shielding film between the light source and the semiconductor layer's depletion region. This film selectively blocks light from reaching the depletion region while allowing the transistor structure to remain simplified. The light shielding film acts as a mediator that prevents the harmful interaction between light and the depletion region without requiring complex structural modifications to the transistor itself.
Solution Approach 2:
The patent segments the functional regions by introducing a dedicated light shielding film that specifically protects the depletion region. This segmentation allows the transistor structure to remain simple overall while isolating the sensitive depletion region from light exposure. The light shielding film creates a distinct functional zone that separates the light-exposed areas from the light-sensitive depletion region.
2Object-affected harmful factors
If a light shielding structure is added to block light from the depletion region, then light leak current is reduced, but the aperture ratio and luminance are reduced
Solution Approach 1:
The patent applies local quality by positioning the light shielding film specifically over the depletion region rather than covering the entire transistor area. The light shielding film is strategically placed only where needed to block light from the depletion region, while leaving the channel region and other functional areas exposed to light. This localized approach maintains high aperture ratio and luminance while effectively reducing light leak current.
Solution Approach 2:
The patent addresses the aperture ratio issue by transitioning to a different dimensional approach. Instead of reducing the planar area occupied by shielding structures, the light shielding film is positioned in the vertical dimension above the depletion region. This allows light blocking to occur in the optical path without consuming valuable pixel area, thereby maintaining high aperture ratio and luminance while effectively shielding the depletion 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 reduces light leak currents and maintains a high aperture ratio, thereby minimizing the reduction in luminance and display quality degradation.
Implementation Method 1
the source wiring or the drain wiring terminates in a region on the gate wiring overlapping the semiconductor layer
Data Source
AI summary
The invention prevents the reduction of a display quality caused by a light leak current of a thin film transistor used in a display device. A lower metal layer is formed on a substrate, and a buffer film, a semiconductor layer, a gate insulation film, and a gate wiring are formed thereon in this order. An interlayer insulation film having contact holes is formed on the gate wiring. A source wiring and a drain wiring connected to a source and a drain of the semiconductor layer through the contact holes respectively extend onto the interlayer insulation film. The source wiring, the drain wiring, and the lower metal layer extend from contact hole side respectively to cover a region that does not extend over an end of the gate wiring in the width direction on or under the semiconductor layer and the gate wiring.