Oxide Semiconductor Transistor Film Stack for Nitrogen Trap Control
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Solution Overview
Problem
The electrical characteristics of transistors using oxide semiconductors are affected by nitrogen content, leading to variations in threshold voltage and reliability issues due to nitrogen acting as a carrier source, similar to hydrogen.
Innovation Solution
A semiconductor device with a gate electrode, oxide semiconductor film, gate insulating film, and protective film is designed, where the protective film has a region with a higher release of gas with a mass-to-charge ratio of 17 than nitrogen oxide, reducing nitrogen concentration and carrier traps, thereby stabilizing the threshold voltage and improving reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If nitrogen is contained in films in contact with oxide semiconductor film, then the transistor can be manufactured with standard processes, but the electrical characteristics change and reliability deteriorates due to nitrogen acting as a carrier source
Solution Approach 1:
A nitrogen barrier film is introduced as an intermediary layer between the oxide semiconductor film and nitrogen-containing films (such as gate insulating films or protective films). This barrier film selectively blocks nitrogen diffusion to the oxide semiconductor film while allowing the device to utilize standard nitrogen-containing insulation processes, thus resolving the contradiction between ease of manufacture and electrical characteristic stability
Solution Approach 2:
The insulation film structure is segmented into multiple functional layers: a nitrogen barrier film specifically positioned to protect the oxide semiconductor film from nitrogen contamination, and other nitrogen-containing films that can be formed using standard processes. This segmentation allows different regions of the device to have different nitrogen content requirements, enabling both manufacturability and reliability
2Ease of manufacture
If hydrogen is present in oxide semiconductor films, then the transistor can be formed with conventional materials, but variation in threshold voltage increases due to hydrogen supplying carriers
Solution Approach 1:
The nitrogen barrier film serves as a protective intermediary that also prevents hydrogen diffusion from nitrogen-containing films into the oxide semiconductor film. This dual protection mechanism maintains process simplicity while improving threshold voltage control by blocking both nitrogen and hydrogen carriers at the interface
Solution Approach 2:
The device structure employs composite material layers with distinct functions: the nitrogen barrier film is specifically designed with low nitrogen and hydrogen content to act as a purification layer, while other layers can use conventional materials. This composite approach enables precise threshold voltage control without complicating the overall manufacturing process
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 solution effectively suppresses changes in electrical characteristics and enhances the reliability of oxide semiconductor transistors by reducing nitrogen-related carrier traps and oxygen vacancies, resulting in improved power efficiency and stability.
Implementation Method 1
a region where the amount of gas having a mass-to-charge ratio m/z of 17 released by heat treatment is greater than the amount of nitrogen oxide released by heat treatment
Data Source
AI summary
To suppress a change in electrical characteristics and to improve reliability in a semiconductor device using a transistor including an oxide semiconductor. The semiconductor device includes a gate electrode over an insulating surface, an oxide semiconductor film overlapping with the gate electrode, a gate insulating film which is between the gate electrode and the oxide semiconductor film and is in contact with a surface of the oxide semiconductor film, a protective film in contact with an opposite surface of the surface of the oxide semiconductor film, and a pair of electrodes in contact with the oxide semiconductor film. In the gate insulating film or the protective film, the amount of gas having a mass-to-charge ratio m/z of 17 released by heat treatment is greater than the amount of nitrogen oxide released by heat treatment.