Oxide Semiconductor Transistor Oxygen Vacancy Reduction
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Solution Overview
Problem
Oxygen vacancies in oxide semiconductor films can shift the threshold voltage of transistors negatively, leading to poor electric characteristics and reliability issues, particularly in semiconductor devices utilizing these films.
Innovation Solution
Incorporating an insulating film with a profile of excess oxygen concentration having two or more local maximum values in the depth direction, which allows for controlled oxygen release at various temperatures, thereby reducing oxygen vacancies and improving the electric characteristics of the transistor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If oxygen vacancies are present in the oxide semiconductor film, then the transistor can be formed more easily, but the threshold voltage shifts negatively and electric characteristics deteriorate
Solution Approach 1:
Oxygen is added to the insulating film before the oxide semiconductor film is formed. This preliminary oxygen incorporation ensures that when the oxide semiconductor film is subsequently formed, oxygen is already available at the interface, preventing oxygen vacancies from forming during the transistor fabrication process. This resolves the contradiction by preparing the oxygen supply in advance, allowing easy transistor formation without the harmful effects of oxygen vacancies.
Solution Approach 2:
An insulating film with excess oxygen is introduced as an intermediary layer between the substrate and the oxide semiconductor film. This insulating film acts as an oxygen reservoir that supplies oxygen to the oxide semiconductor film during or after its formation. The insulating film mediates the oxygen transfer process, ensuring adequate oxygen supply to prevent vacancies while maintaining ease of manufacturing.
2Device complexity
If a single oxygen addition condition is used, then the process is simpler, but oxygen cannot be supplied at a wide range of temperatures
Solution Approach 1:
The oxygen addition process is segmented into multiple steps, each with different oxygen addition conditions (such as different plasma power, gas flow rates, or pressure conditions). This segmentation creates distinct oxygen concentration profiles within the insulating film, with different regions having oxygen released at different temperatures. This resolves the contradiction by dividing the oxygen supply into multiple controllable segments, enabling wide temperature adaptability while maintaining reasonable process complexity.
Solution Approach 2:
Different parameters of the oxygen addition process are changed between steps, such as plasma power, oxygen flow rate, pressure, or addition timing. These parameter changes create varying oxygen concentration distributions in the insulating film, which correspond to different oxygen release temperatures. This allows the system to adapt to a wide temperature range while keeping each individual step relatively simple.
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 method effectively reduces oxygen vacancies in oxide semiconductor films and their vicinity, enhancing the electric characteristics and reliability of semiconductor devices by supplying oxygen at a wide range of temperatures, resulting in improved transistor performance.
Implementation Method 1
the insulating film having different conditions of oxygen release can release oxygen at a wide range of temperatures in the case where the oxygen is released by heat treatment
Data Source
AI summary
Oxygen vacancies in an oxide semiconductor film and the vicinity of the oxide semiconductor film are reduced and electric characteristics of a transistor including the oxide semiconductor film are improved. Further, a highly reliable semiconductor device including the transistor including the oxide semiconductor film is provided. In the transistor including the oxide semiconductor film, at least one insulating film in contact with the oxide semiconductor film contains excess oxygen. By the excess oxygen included in the insulating film in contact with the oxide semiconductor film, oxygen vacancies in the oxide semiconductor film and the vicinity of the oxide semiconductor film can be reduced. Note that the insulating film including the excess oxygen has a profile of the excess oxygen concentration having two or more local maximum values in the depth direction.