Display Device Insulating Film Thickness Optimization
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Solution Overview
Problem
In liquid crystal display devices, the dielectric film of the capacitor element and the gate insulating film of the thin-film transistor are typically formed using the same material and thickness, which can lead to inadequate film thickness for optimal performance, increasing parasitic capacitance and reducing drive speed.
Innovation Solution
A display device structure where the thin-film transistor and capacitor element use insulating films formed in different layers, with a polycrystalline semiconductor layer and selective etching to expose high concentration areas, allowing for independent film thickness settings without increasing manufacturing processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the dielectric film of the capacitor element and the gate insulating film of the thin-film transistor are formed using the same material and thickness, then the manufacturing process is simplified, but the film thickness cannot be optimized for each component's specific characteristics
Solution Approach 1:
The patent divides the insulating film formation into separate layers: a first insulating film for the gate insulating function and a second insulating film for the dielectric function. This segmentation allows each film to have independently optimized thickness while being formed in the same manufacturing step, thus simplifying the process while improving component performance.
2Speed
If the film thickness is increased to reduce parasitic capacitance, then the drive speed improves, but the film thickness may become excessive for the gate insulating film
Solution Approach 1:
The patent applies different thickness specifications to different insulating films based on their specific functions. The first insulating film (gate insulating film) has a thickness optimized for transistor operation, while the second insulating film (dielectric film) has a greater thickness optimized for reducing parasitic capacitance. This local quality approach allows each component to have appropriate film thickness without compromising overall device performance.
3Reliability
If separate manufacturing processes are used for the gate insulating film and dielectric film, then the film thickness can be independently optimized, but the number of manufacturing processes increases
Solution Approach 1:
The patent combines the formation of the first insulating film and second insulating film into a single manufacturing step where both layers are deposited simultaneously or in sequence without intermediate processing steps. This merging approach allows independent thickness control of each film while avoiding the complexity of separate manufacturing processes.
Data Source
AI summary
Provided is a display device including a thin-film transistor and a capacitor element, the thin-film transistor includes: a first insulating film (IN1) which is formed to cover an area where a gate electrode (GT) is formed; a second insulating film (IN2) which is formed on the first insulating film, the second insulating film having an opening (OP) formed in the area in plan view; a semiconductor layer (SCLt) which is formed on the second insulating film to cross the opening, the semiconductor layer including high concentration areas (CN); a third insulating film (IN3) which is formed on the semiconductor layer to expose apart of each of the high concentration areas; and a pair of electrodes (DT, ST) each having electrical connection to the part; and the capacitor element includes a dielectric film which is formed of the same layer and the same material as the third insulating film.