Transistor Drain Region Structure for Leakage Suppression
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Solution Overview
Problem
In display apparatuses using organic EL elements, leakage currents in drive transistors can lead to bright spots on the display, degrading image quality due to high electric fields and increased luminance signal variations.
Innovation Solution
The design incorporates a specific structure for the drain regions of transistors, including regions with higher resistivity and lower impurity concentrations, and using semiconductor and metal compound regions to reduce electric field stress and leakage currents, thereby improving transistor performance and image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the LDD length of the switching transistor is increased to suppress leakage current, then the leakage current is reduced, but the device complexity and manufacturing precision requirements increase
Solution Approach 1:
The patent applies local quality by creating distinct regions within the drain structure: a first drain region with higher impurity concentration and a second drain region with lower impurity concentration. This gradient structure locally optimizes each region's properties - the first region provides low resistance while the second region suppresses leakage current through reduced electric field stress, thereby resolving the contradiction between leakage suppression and device complexity.
Solution Approach 2:
The drain region is segmented into multiple sub-regions with different impurity concentrations. The first drain region (higher impurity concentration) and second drain region (lower impurity concentration) are separated by a junction, creating distinct functional zones that collectively achieve both low resistance and leakage suppression without requiring excessive overall complexity.
2Speed
If a high electric field is applied to the drain region to improve transistor performance, then the transistor speed increases, but leakage current between source-drain or drain-well regions increases significantly
Solution Approach 1:
The patent changes the impurity concentration parameter across the drain region to resolve the contradiction. By creating a gradient from high impurity concentration (first drain region) to low impurity concentration (second drain region), the structure maintains low resistance for fast operation while the low-concentration region reduces electric field stress to suppress leakage current, achieving both speed and low leakage.
3Reliability
If the impurity concentration in the drain region is increased to reduce resistance, then the current flow improves, but the electric field stress increases causing more leakage current
Solution Approach 1:
The patent implements local quality by assigning different impurity concentrations to different parts of the drain region. The first drain region has high impurity concentration to ensure low resistance and efficient current flow, while the second drain region has low impurity concentration to reduce electric field stress and suppress leakage current. This spatial differentiation of material properties resolves the contradiction between current efficiency and leakage suppression.
Data Source
AI summary
A display apparatus including pixels is provided. Each pixels comprises a light-emitting element, a first transistor having a drain region connected to an anode of the light-emitting element, and a second transistor having a drain region connected to a gate electrode of the first transistor. The drain region of the first transistor includes a first region and a second region arranged between the first region and a channel region and having a higher resistivity than the first region. The drain region of the second transistor includes a third region and a fourth region arranged between the third region and a channel region and having a higher resistivity than the third region. A length of the second region in a direction in which a current flows is longer than that of the fourth region in a direction in which a current flows.