Access Transistor Metal Oxide Barrier for Hydrogen Diffusion Control
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Solution Overview
Problem
Existing thin film transistor (TFT) technologies face challenges in maintaining the threshold voltage due to high hydrogen diffusion from the gate electrode into the channel, which is exacerbated by the use of metallic gate materials with high work function, leading to limited electrostatic control.
Innovation Solution
Incorporating a semiconducting metal oxide liner as a barrier layer to reduce hydrogen diffusion and enhance the threshold voltage of transistors by acting as a barrier between the gate electrode and the channel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If metallic gate materials with high work function are used, then the threshold voltage is enhanced, but hydrogen diffusion into the channel increases
Solution Approach 1:
A metal oxide barrier layer is introduced as an intermediary between the metallic gate electrode and the oxide semiconductor channel. This barrier layer has low hydrogen permeability, blocking hydrogen diffusion from the gate electrode into the channel while allowing the high work function metal to maintain its threshold voltage enhancement effect.
Solution Approach 2:
The gate structure is segmented into multiple functional layers: the metallic gate electrode for work function control, the metal oxide barrier layer for hydrogen blocking, and the gate dielectric layer for electrical isolation. This segmentation allows each layer to independently perform its specific function without interfering with others.
2Reliability
If metallic gate materials with high work function are used, then electrostatic control is improved, but hydrogen diffusion from gate electrode into channel is exacerbated
Solution Approach 1:
The metal oxide barrier layer serves as a mediator that preserves the electrostatic control benefits of high work function metals while eliminating their harmful hydrogen diffusion effect. The barrier layer is positioned between the gate electrode and channel, allowing electrical field control to pass through while blocking hydrogen atoms.
Solution Approach 2:
The gate structure uses a composite material approach, combining metallic materials for electrostatic control with metal oxide materials for hydrogen barrier properties. This composite structure integrates the advantages of different material classes while mitigating their individual disadvantages.
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 semiconducting metal oxide liner effectively increases the threshold voltage of TFTs, providing improved electrostatic control and reducing hydrogen diffusion, thereby enhancing the performance of thin film transistors.
Implementation Method 1
a first barrier layer comprising a metal oxide and having a first hydrogen permeability; a second barrier layer comprising a metal oxide and having a second hydrogen permeability, the second hydrogen permeability being less than the first hydrogen permeability
Implementation Method 2
the gate electrode and the gate dielectric layer, wherein the gate dielectric layer directly contacts the top surface of the active layer
Data Source
AI summary
A transistor may be provided by forming, in a forward order or in a reverse order, a gate electrode, a semiconducting metal oxide liner, a gate dielectric, and an active layer over a substrate, and by forming a source electrode and a drain electrode on end portions of the active layer. The semiconducting metal oxide liner comprises a thin semiconducting metal oxide material that functions as a hydrogen barrier material.