Oxide Semiconductor Display Circuit Layout for Speed and Aperture
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Solution Overview
Problem
In display devices, the increased pixel density leads to reduced writing time for display images, necessitating high-speed operation of transistors in driver circuits while maintaining high on-off ratios and aperture ratios in pixel portions, which is challenging due to the conflicting requirements of switching characteristics and operational speed.
Innovation Solution
A display device structure is developed with both pixel and driver circuits on one substrate, utilizing transistors with specific gate and source/drain electrode configurations, along with oxide semiconductor and insulating layers, optimized for high-speed operation and light-transmitting properties to enhance aperture ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pixel density is increased to improve display resolution, then display quality is improved, but writing time is reduced and aperture ratio decreases
Solution Approach 1:
The patent changes the material parameter of the transistor channel from conventional semiconductor to oxide semiconductor, which fundamentally alters the electrical characteristics to achieve higher field-effect mobility. This enables the transistor to operate faster, compensating for the reduced writing time caused by increased pixel density
Solution Approach 2:
The patent employs different transistor structures with optimized characteristics for different circuit functions: pixels use transistors with high on-off ratio for stable holding, while driver circuits use transistors with high field-effect mobility for fast operation. This dynamic optimization allows the system to meet both speed and accuracy requirements simultaneously
2Measurement precision
If pixel density is increased to improve display resolution, then display quality is improved, but aperture ratio decreases
Solution Approach 1:
The patent changes the material composition of transistor components to light-transmitting materials, specifically making the gate electrode layer, source electrode layer, and drain electrode layer transparent or semi-transparent. This reduces the optical shadow area of the transistor, thereby increasing the aperture ratio while maintaining high pixel density
Solution Approach 2:
The patent applies color/transparency optimization by selecting materials with light-transmitting properties for the transistor electrodes. This allows the transistor structure to be optically invisible or minimally visible, maximizing the effective display area and aperture ratio
3Ease of manufacture
If conventional transistor structures are used to simplify manufacturing, then ease of manufacture is improved, but switching characteristics and operation speed cannot meet both pixel and driver circuit requirements
Solution Approach 1:
The patent segments the transistor population by function: pixels use one transistor structure optimized for high on-off ratio (stable signal holding), while driver circuits use another structure optimized for high field-effect mobility (fast switching). This segmentation allows each circuit type to have optimized characteristics without compromising the other
Solution Approach 2:
The patent uses oxide semiconductor material as a universal channel layer for all transistors on the substrate, providing a common foundation that delivers both high on-off ratio and high field-effect mobility. This universal material platform simplifies manufacturing while enabling differentiated performance through structural optimization
Data Source
AI summary
An object is to provide a display device with excellent display characteristics, where a pixel circuit and a driver circuit provided over one substrate are formed using transistors which have different structures corresponding to characteristics of the respective circuits. The driver circuit portion includes a driver circuit transistor in which a gate electrode layer, a source electrode layer, and a drain electrode layer are formed using a metal film, and a channel layer is formed using an oxide semiconductor. The pixel portion includes a pixel transistor in which a gate electrode layer, a source electrode layer, and a drain electrode layer are formed using an oxide conductor, and a semiconductor layer is formed using an oxide semiconductor. The pixel transistor is formed using a light-transmitting material, and thus, a display device with higher aperture ratio can be manufactured.