TFT Edge Region Doping to Suppress Kink Effect
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Solution Overview
Problem
Conventional thin film transistors (TFTs) suffer from edge effects and kink effects, which deteriorate their characteristics and lead to issues like threshold voltage changes and sudden increases in drain current, due to damaged edge portions and parasitic bipolar junction transistor (BJT) effects.
Innovation Solution
The TFT design includes an edge region doped with impurities of a conductivity type opposite to those in the source and drain regions, with an interconnection portion connecting the edge region to the source region, which helps in reducing edge and kink effects by ensuring current flows only through the channel region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional TFT structure is used, then manufacturing is simple, but edge effect and kink effect occur causing deteriorated characteristics
Solution Approach 1:
The semiconductor layer is segmented into distinct regions: source region, drain region, channel region, and edge region. The edge region is further segmented by introducing impurity regions with opposite conductivity type to create a structured barrier against edge effects and kink effects, while maintaining overall device functionality.
Solution Approach 2:
Different regions of the semiconductor layer are assigned different impurity doping characteristics. Specifically, the edge region contains impurity regions with conductivity type opposite to the source and drain regions, creating localized electrical properties that counteract edge effects and kink effects without affecting the main channel operation.
2Reliability
If edge region is doped with opposite conductivity type impurities, then edge effect and kink effect are reduced, but manufacturing process complexity increases
Solution Approach 1:
The opposite conductivity type impurity regions are formed in the edge region before the main semiconductor layer fabrication is completed. This preliminary action prevents edge effects and kink effects from developing during subsequent processing steps, ensuring stable drain current characteristics from the outset.
Solution Approach 2:
The conductivity type parameter of the edge region is changed by introducing impurities with opposite polarity to the source and drain regions. This parameter change creates an electrical barrier that suppresses edge effects and kink effects, improving drain current characteristics without requiring fundamental process changes.
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 approach effectively reduces edge and kink effects, resulting in improved drain current characteristics and a low sub-threshold voltage swing at low gate voltages, thereby enhancing the overall performance of TFTs.
Implementation Method 1
an edge region interposed between the channel region and the source region, and doped with impurities of a conductivity type opposite to a conductivity type of impurities to be doped into source and drain regions
Data Source
AI summary
A thin film transistor (TFT), a method of fabricating the same, and a display device including the TFT, are provided. The method includes forming an edge region that is doped with impurities of a conductivity type opposite to a conductivity type of impurities doped into source and drain regions. The edge region is in contact with a channel region and an edge portion of the source region. The method also includes forming contact holes for source and drain electrodes to expose a portion of the drain region and expose respective portions of the source region and the edge region contacting the edge portion of the source region; and forming source and drain electrodes. Thus, a source-body contact is automatically formed so that an edge effect can be reduced and a kink effect can be reduced or removed.