Display Device Driving Transistor Recess Channel Length
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Solution Overview
Problem
The increasing fineness of display elements and driving transistors in display devices leads to higher threshold voltage variation, resulting in decreased uniformity of display images due to increased on-current variation, especially when gate voltage is reduced to match the lower current requirements.
Innovation Solution
A display device with a driving transistor featuring a first-conductivity-type activation region, an opening crossing the activation region, a gate insulating film, and second-conductivity-type diffusion regions, allowing for a longer effective channel length without increasing the transistor's area, thereby reducing on-current variation and improving image uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If display elements and driving transistors are made finer to improve resolution, then resolution is improved, but threshold voltage variation increases and uniformity of display image decreases
Solution Approach 1:
The patent changes the physical parameters of the transistor by introducing a recess structure that increases the channel length from L to L+2d (where d is the recess depth). This parameter change allows the channel length to be extended without increasing the planar area, thereby reducing on-current and making the system less sensitive to threshold voltage variations while maintaining high resolution
Solution Approach 2:
The patent transitions from a two-dimensional planar channel to a three-dimensional channel with vertical recess. By etching recesses into the semiconductor substrate and filling them with gate material, the channel length is extended in the vertical dimension while maintaining the same footprint area, thus achieving longer channel length without increasing device area
2Use of energy by moving object
If gate voltage is reduced to match lower current requirements of finer display elements, then current matching is improved, but on-current variation between driving transistors increases
Solution Approach 1:
The patent changes the channel length parameter by introducing recess structures, which reduces the on-current to an appropriate level for driving fine display elements. The extended channel length (L+2d) provides better current control without requiring gate voltage reduction, thereby maintaining uniformity while achieving current matching
3Reliability
If channel length is increased to reduce on-current variation, then uniformity is improved, but transistor area increases
Solution Approach 1:
The patent resolves this contradiction by extending the channel in the vertical dimension through recess structures. The channel length increases from L to L+2d while the planar area remains constant, as the recesses utilize the vertical space within the existing transistor footprint rather than expanding horizontally
Data Source
AI summary
[Object] To provide a display device that displays a display image with high resolution and higher uniformity, and an electronic apparatus including the display device.[Solution] A display device including: a driving transistor including a first-conductivity-type activation region provided in a semiconductor substrate, an opening provided to cross the activation region, a gate insulating film provided on the activation region including an inside of the opening, a gate electrode filling the opening, and second-conductivity-type diffusion regions provided on both sides of the activation region across the opening; and an organic electroluminescent element configured to be driven by the driving transistor.