Thin Film Transistor Gate Insulator Density Gradient
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Solution Overview
Problem
In thin film transistors used in active-matrix displays, the increase in line length due to larger display screens leads to higher line resistance and current losses, which is exacerbated by the need to thicken gate electrodes while maintaining thin gate insulating films to improve transistor characteristics, resulting in degraded voltage endurance characteristics.
Innovation Solution
A thin film transistor design featuring a gate insulating layer with distinct high-density and low-density areas made of the same substance, where the high-density area is above the gate electrode and the low-density area is between gate electrodes, improving voltage endurance and reducing parasitic capacitance, allowing for thicker lines with reduced resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the gate electrode is thickened to reduce line resistance, then line resistance decreases, but the voltage endurance characteristics of the gate insulating film deteriorate
Solution Approach 1:
The gate insulating film is designed with different thicknesses in different regions: a first region with greater thickness above the gate electrode for high voltage endurance, and a second region with smaller thickness elsewhere for low parasitic capacitance. This local differentiation resolves the contradiction by optimizing each region for its specific function.
Solution Approach 2:
The gate insulating film is segmented into multiple regions with different thickness characteristics. The first region (above gate electrode) and second region (between gate electrodes) are structurally separated in terms of thickness, allowing independent optimization of voltage endurance and parasitic capacitance.
2Productivity
If the gate insulating film is thinned to improve thin film transistor characteristics, then TFT characteristics improve, but the voltage endurance characteristics deteriorate
Solution Approach 1:
Different regions of the gate insulating film have different thicknesses optimized for different functions: the first region above the gate electrode maintains greater thickness for voltage endurance, while the second region has reduced thickness for improved TFT characteristics and reduced parasitic capacitance.
Solution Approach 2:
The gate insulating film is divided into functional segments where the first region preserves thickness for reliability while the second region reduces thickness for performance, allowing simultaneous optimization of both voltage endurance and TFT characteristics.
3Area of stationary object
If display size increases to meet market demand, then display area increases, but line length and line resistance increase
Solution Approach 1:
The gate electrode thickness is optimized in specific regions: thicker gate electrodes are provided above the semiconductor layer where current conduction is critical, while other regions maintain standard thickness. This local optimization reduces line resistance in critical paths without increasing overall device complexity.
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 design enhances voltage endurance and TFT characteristics, enabling lower line resistance and higher-speed operation in organic EL light emitting devices, even as display sizes increase, by maintaining high-density carrier induction and reducing point discharges and parasitic capacitance.
Implementation Method 1
the gate insulating layer includes a first area and a second area, the first area being above the gate electrode, the second area being different from an area above the gate electrode, and made of a same substance as the first area, the first area has a higher density than a density of the second area
Data Source
AI summary
A thin film transistor according to the present disclosure including: a gate electrode above a substrate; a gate insulating layer covering the gate electrode; a semiconductor layer above the gate insulating layer; and a source electrode and a drain electrode which are above the gate insulating layer, and electrically connected to the semiconductor layer, in which the gate insulating layer includes a first area and a second area, the first area being above the gate electrode, the second area being different from an area above the gate electrode, and made of a same substance as the first area, and the first area has a higher density than a density of the second area.