Laminated Light Blocking Films for Liquid Crystal Display Transistors
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Solution Overview
Problem
Existing liquid crystal displays face issues with light leakage current due to the degradation of light blocking properties in the gate electrode materials during the annealing process, which affects the image quality and pixel uniformity.
Innovation Solution
The implementation of a laminated structure with an upper side light blocking film and a lower side light blocking film, where the upper side light blocking film is formed after the annealing process to maintain its optical density and effectively block light from entering the semiconductor layer, while the lower side light blocking film is connected to the upper side film to enhance light blocking performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the gate electrode is made of light blocking material (TiN, WSi) and exposed to high temperature during annealing process, then the impurities are activated in the semiconductor layer, but the OD value of the gate electrode is lowered and light blocking property is deteriorated
Solution Approach 1:
The light blocking function is divided into two separate components: the gate electrode (for electrical control) and the light blocking film (for optical shielding). This segmentation allows the light blocking film to be optimized for high OD value without being exposed to annealing temperatures, while the gate electrode performs its electrical function independently.
Solution Approach 2:
The light blocking film is formed before the annealing process to protect the semiconductor layer from light during subsequent processing steps. By performing this action preliminarily, the patent avoids the need to maintain high OD value through the annealing process, as the light blocking function is already established.
2Manufacturing precision
If the gate electrode functions as both electrical control and light blocking, then the TFT can be formed in self-aligning manner, but the light blocking property is reduced due to annealing process
Solution Approach 1:
The dual function of the gate electrode is segmented into separate components: the gate electrode itself for electrical control and a dedicated light blocking film for optical shielding. This allows the gate electrode to be formed in a self-aligning manner while the light blocking film provides the necessary optical protection without being compromised by thermal processes.
Solution Approach 2:
The light blocking film acts as an intermediary layer between the gate electrode and the incident light. It mediates the conflict between electrical control and optical blocking functions by absorbing the light blocking requirement, allowing the gate electrode to focus solely on electrical control while maintaining self-alignment benefits.
3Device complexity
If a single light blocking layer is used, then the structure is simpler, but the light blocking performance is insufficient to sufficiently decrease light leakage current
Solution Approach 1:
The patent employs a composite laminated structure consisting of multiple layers with different functions: the gate electrode layer, the light blocking film layer, and the insulating film layer. This composite structure combines the electrical control capability of the gate electrode with the high OD value light blocking capability of the dedicated light blocking film, achieving superior overall performance.
Solution Approach 2:
The patent adds a vertical dimension to the light blocking strategy by stacking multiple functional layers. Instead of relying on a single planar layer, the laminated structure creates a multi-dimensional barrier against light, with each layer contributing to the overall light blocking performance through its specific properties and positioning.
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 significantly reduces light leakage current and maintains high light blocking performance, ensuring improved image quality and reduced flickering or pixel unevenness in liquid crystal displays.
Implementation Method 1
an upper side light blocking film that is formed to have a part overlapping with the gate electrode further to the upper layer side than the gate electrode via an upper side insulating film
Implementation Method 2
these materials are exposed to high temperature due to the annealing process, the OD value is lowered
Data Source
AI summary
An electric optical device includes a transistor that includes a semiconductor layer having a source region connected to a data line, a drain region connected to a pixel electrode, and a channel region, and a gate electrode, a first light blocking film that is formed to be wider than the gate electrode and that is connected to the gate electrode via a first contact hole which is opened in a first insulating film disposed on the gate electrode, and a second light blocking film that is provided between the semiconductor layer and a substrate and is connected to the first light blocking film via a second contact hole which is opened to penetrate the first insulating film, a gate insulating film, and a second insulating film.