Oxide Semiconductor Transistor Capacitor Aperture Ratio
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Solution Overview
Problem
Display devices using oxide semiconductors face issues with variations in electrical characteristics, particularly threshold voltage changes, leading to increased power consumption and decreased contrast due to normally-on transistor characteristics, limiting improvements in display quality and aperture ratio.
Innovation Solution
A display device with a transistor incorporating an oxide semiconductor film, a capacitor with increased capacitance, and a light-emitting element formed over an inorganic insulating film, using a metal oxide film as one electrode and a light-transmitting conductive film as the other, to enhance electrical characteristics and aperture ratio while reducing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If oxide semiconductor transistors are used in display devices, then manufacturing cost is reduced and flexibility is improved, but electrical characteristics vary and threshold voltage changes occur
Solution Approach 1:
The patent applies parameter changes by optimizing the oxide semiconductor composition (In-Ga-Zn-O system with specific atomic ratios), controlling deposition conditions (temperature, oxygen partial pressure), and adjusting film thickness to achieve stable electrical characteristics while maintaining low-cost manufacturing
Solution Approach 2:
The patent uses composite materials by combining multiple oxide layers (In-Ga-Zn-O semiconductor layer with Ga-rich and In-rich regions) in a single transistor structure to achieve both low-cost manufacturing and stable electrical characteristics through material composition optimization
2Use of energy by moving object
If aperture ratio is increased to reduce power consumption, then power consumption is reduced, but capacitor capacitance decreases and charge holding becomes insufficient
Solution Approach 1:
The patent applies parameter changes by increasing the capacitor area and optimizing the dielectric layer composition (using high-k materials) to maintain sufficient capacitance even with larger aperture ratios, enabling reduced power consumption while preserving charge holding capability
3Loss of energy
If normally-on characteristics are used in oxide semiconductor transistors, then off-state current is reduced, but malfunctions occur during operation and contrast decreases
Solution Approach 1:
The patent applies parameter changes by precisely controlling the oxide semiconductor film properties (carrier concentration, mobility, thickness) and transistor structure parameters to achieve normally-off characteristics with extremely low off-state current, eliminating malfunctions while maintaining energy efficiency
Data Source
AI summary
A display device having a high aperture ratio and including a capacitor that can increase capacitance is provided. A pair of electrodes of the capacitor is formed using a light-transmitting conductive film. One of the electrodes of the capacitor is formed using a metal oxide film, and the other of the electrodes of the capacitor is formed using a light-transmitting conductive film. With such a structure, light can be emitted to the capacitor side when an organic insulating film is provided over the capacitor and a pixel electrode of a light-emitting element is formed over the organic insulating film. Thus, the capacitor can transmit light and can overlap the light-emitting element. Consequently, the aperture ratio and capacitance can be increased.