Oxide Semiconductor Transistor Oxygen Supply via Source Drain Regions
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Solution Overview
Problem
The challenge is to efficiently supply oxygen to the channel formation region of a transistor using an oxide semiconductor, as oxygen desorption affects electrical characteristics, and existing methods do not effectively address oxygen vacancy issues.
Innovation Solution
A transistor design with a source region and drain region having higher oxygen concentrations than the channel formation region, utilizing a c-axis aligned crystal channel formation region and amorphous source/drain regions, along with an impurity for improved conductivity, and an aluminum oxide insulating film to prevent impurity penetration, combined with a method involving sequential steps of forming electrodes and performing heat treatment to optimize oxygen supply.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If heat treatment is performed for dehydration or dehydrogenation on the oxide semiconductor layer, then hydrogen and moisture are removed improving electrical characteristics, but oxygen is desorbed creating oxygen vacancies that worsen electrical characteristics
Solution Approach 1:
Oxygen is supplied to the oxide semiconductor layer before heat treatment for dehydration or dehydrogenation. This preliminary oxygen supply ensures that when oxygen is desorbed during subsequent heating, the oxygen vacancies can be filled, preventing degradation of electrical characteristics while still achieving the desired removal of hydrogen and moisture.
Solution Approach 2:
An insulating film containing oxygen is formed in contact with the oxide semiconductor layer before heat treatment. This insulating film acts as an oxygen reservoir that can supply oxygen to the oxide semiconductor layer during heating, cushioning against the oxygen loss that would otherwise occur and create harmful vacancies.
2Adaptability or versatility
If the oxide semiconductor layer is used as a channel formation region, then transistor functionality is achieved, but oxygen vacancies from oxygen desorption during heat treatment degrade electrical characteristics
Solution Approach 1:
Oxygen is supplied to the oxide semiconductor layer forming the channel region before heat treatment. This ensures that when the layer is subsequently heated for dehydration or dehydrogenation, oxygen vacancies that would form in the channel region can be filled, maintaining the electrical characteristics necessary for proper transistor functionality.
Solution Approach 2:
An insulating film containing oxygen is introduced as an intermediary between the oxide semiconductor channel layer and the external environment. This intermediate layer supplies oxygen to the channel formation region during heat treatment, mediating the conflict between removing impurities and maintaining oxygen content for proper electrical characteristics.
3Reliability
If conventional heat treatment methods are used for dehydration or dehydrogenation, then hydrogen and moisture are removed, but oxygen loss creates oxygen vacancies requiring additional oxygen supply methods
Solution Approach 1:
The oxygen supply function is merged with the insulating film that is already part of the transistor structure. By forming the insulating film to contain oxygen and place it in contact with the oxide semiconductor layer, the oxygen supply capability is combined with the insulating function, eliminating the need for separate oxygen supply processes and reducing overall device complexity.
Solution Approach 2:
The insulating film is designed to serve multiple functions: providing electrical insulation and simultaneously serving as an oxygen reservoir to supply oxygen to the oxide semiconductor layer during heat treatment. This multi-functionality reduces the need for additional dedicated oxygen supply structures or processes.
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 approach allows for efficient oxygen supply to the channel region, enhancing electrical characteristics and stability of the transistor by filling oxygen vacancies, thereby improving performance and reliability.
Implementation Method 1
heat treatment performed as dehydration or dehydrogenation treatment on the oxide semiconductor layer
Implementation Method 2
heat treatment performed as dehydration or dehydrogenation treatment on the oxide semiconductor layer
Implementation Method 3
oxygen is supplied to the oxide semiconductor layer through heat treatment performed as dehydration or dehydrogenation treatment
Data Source
AI summary
A transistor excellent in electrical characteristics and a method for manufacturing the transistor are provided. The transistor includes an oxide semiconductor layer including a source region, a drain region, and a channel formation region over an insulating surface; a gate insulating film over the oxide semiconductor layer; a gate electrode overlapping with the channel formation region, over the gate insulating film; a source electrode in contact with the source region; and a drain electrode in contact with the drain region. The source region and the drain region include a portion having higher oxygen concentration than the channel formation region.