Oxide Semiconductor TFT Gate Structure Against Oxygen Depletion
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Solution Overview
Problem
In semiconductor devices using TFTs with oxide semiconductors, the metal gate electrodes can deprive the oxide semiconductors of oxygen through the gate insulating film, leading to non-operation of the TFTs, especially when oxygen is removed from the channel region.
Innovation Solution
A semiconductor device structure is implemented where a metal nitride or metal oxide film is formed on the top surface of the gate electrode opposing the channel region, while leaving parts of the gate electrode surface uncovered, thereby preventing oxygen depletion from the oxide semiconductor channel region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a metal gate electrode is used in a TFT with oxide semiconductor, then the electrical conductivity and mobility are improved, but oxygen is depleted from the oxide semiconductor channel region causing the TFT to become conductive and non-operational
Solution Approach 1:
An aluminum oxide insulating film is introduced as an intermediary layer between the metal gate electrode and the oxide semiconductor channel region. This intermediary film prevents direct oxygen transfer from the oxide semiconductor to the metal gate electrode, thereby maintaining the oxygen content and insulating properties of the channel region while allowing the metal gate to function electrically through the gate insulating film.
Solution Approach 2:
The gate structure is segmented into multiple functional layers: the metal gate electrode for electrical function, the aluminum oxide insulating film for oxygen barrier function, and the gate insulating film for electrical isolation. This segmentation allows each layer to perform its specific function without interfering with the others, preventing oxygen depletion while maintaining electrical performance.
2Reliability
If aluminum wiring is used to reduce wiring resistance, then the electrical conductivity is improved, but the wiring becomes prone to breakage due to electromigration or stress migration
Solution Approach 1:
The wiring structure uses a composite material approach by combining aluminum with other materials in a multi-layer configuration. The aluminum layer provides low electrical resistance, while surrounding or adjacent layers (such as barrier films or support structures) provide mechanical strength and resistance to electromigration and stress migration, creating a composite wiring system that achieves both electrical and mechanical performance.
3Ease of manufacture
If ITO film and Al wiring are directly connected to reduce manufacturing complexity, then the process is simplified, but Al deprives oxygen from ITO preventing electrical connection
Solution Approach 1:
An aluminum oxide insulating film serves as an intermediary layer between the ITO film and Al wiring connection points. This intermediary film prevents oxygen depletion from the ITO by aluminum, thereby maintaining the electrical properties of the ITO while still allowing for effective electrical connection through the structured interface, balancing manufacturing simplicity with connection reliability.
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 configuration effectively prevents oxygen depletion from the oxide semiconductor channel region, ensuring stable operation of the TFTs by maintaining high resistance and preventing conductive metallization of the oxide semiconductor.
Implementation Method 1
a metal nitride film is formed on a top surface of the gate electrode in an opposing portion to the channel region in a plan view; and the metal nitride film is not formed at a part of the top surface of the gate electrode
Implementation Method 2
When oxygen is removed, an oxide semiconductor becomes metallized and becomes conductive
Implementation Method 3
a gate insulating film is formed on the gate electrode, and an oxide semiconductor film is provided on the gate insulating film
Implementation Method 4
when oxygen is removed from a channel region, a TFT becomes conductive, and the operation as a TFT becomes impossible
Data Source
AI summary
The purpose of the present invention is to suppress a change in characteristics of a TFT using an oxide semiconductor film caused by that oxygen in the oxide semiconductor film is extracted by metal electrode. The main structure of the present invention is as follows. A semiconductor device having a TFT, in which a gate insulating film is formed on a gate electrode, and an oxide semiconductor film is formed on the gate insulating film; the oxide semiconductor film including a channel region, a drain region, and a source region; in which a metal nitride film is formed on a top surface of the gate electrode in an opposing portion to the channel region in a plan view; and the metal nitride film is not formed at a part of the top surface of the gate electrode.