Thin-Film Transistor LDD Structure for Hot Carrier Reliability
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Solution Overview
Problem
Existing thin-film transistors face challenges in miniaturization due to short-channel effects, leading to hot carrier generation and leakage currents, which affect the reliability and performance of organic light-emitting display devices.
Innovation Solution
A thin-film transistor design incorporating a channel region with source and drain regions doped with a first element and lightly doped regions doped with a second element, where the diffusion coefficient of the second element is greater, forming a silicide structure and an LDD (Lightly Doped Drain) structure, which reduces hot carrier generation and improves reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the transistor channel length is reduced for miniaturization, then the device size is reduced, but short-channel effects increase causing hot carrier generation and leakage currents
Solution Approach 1:
The patent applies local quality by creating regions with different doping concentrations within the active layer. Specifically, lightly doped regions are formed adjacent to the source and drain regions, while the channel region maintains a different doping level. This spatial variation in doping quality allows the transistor to be miniaturized while the lightly doped regions locally mitigate short-channel effects and reduce hot carrier generation, thus maintaining reliability despite reduced channel length.
2Reliability
If heavily doped source and drain regions are used to improve conductivity, then electrical conductivity is improved, but hot carrier generation increases
Solution Approach 1:
The patent implements local quality by introducing lightly doped regions between the heavily doped source/drain regions and the channel. The source and drain regions maintain heavy doping for good conductivity, while the adjacent lightly doped regions locally reduce the doping concentration to minimize hot carrier generation. This spatial differentiation in doping quality resolves the contradiction between maintaining electrical conductivity and reducing hot carrier effects.
Solution Approach 2:
The lightly doped regions act as intermediary zones between the heavily doped source/drain regions and the channel. These intermediary regions with moderate doping levels serve as a transition zone that reduces the abrupt doping junction, thereby decreasing hot carrier generation while still allowing effective charge transport. This mediator approach balances the conflicting requirements of conductivity and hot carrier suppression.
3Productivity
If the channel width is reduced to increase pixel density, then display resolution is improved, but leakage currents increase due to short-channel effects
Solution Approach 1:
The patent applies local quality by forming lightly doped regions adjacent to the source and drain regions within the active layer. This localized variation in doping concentration allows the channel width to be reduced for higher pixel density while the lightly doped regions locally compensate for short-channel effects, thereby controlling leakage currents even in narrow channel transistors with improved pixel density.
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
The design enhances the current characteristics and reliability of the thin-film transistor, reducing leakage currents and improving punch-through characteristics, even with miniaturization, by effectively managing the diffusion of elements and forming a stable silicide structure.
Implementation Method 1
a diffusion coefficient of the second element with respect to silicon may be greater than a diffusion coefficient of the first element with respect to silicon
Implementation Method 2
forming an active layer by crystallizing the amorphous silicon layer
Implementation Method 3
Forming the one pair of precursor layers may be performed by a sputtering method using a target including the first and second elements
Data Source
AI summary
A thin-film transistor, including a substrate; an active layer on the substrate; a gate electrode on the active layer; and a gate insulating layer between the active layer and the gate electrode, the active layer including a channel region; source and drain regions at opposite sides of the channel region; and lightly doped regions between the channel region and the source region and between the channel region and the drain region, the source and drain regions being doped with a first element, and the lightly doped regions being doped with a second element different from the first element.