Crystalline Oxide Semiconductor Film Stabilization via Aluminum Oxide Shielding
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Oxide semiconductor transistors exhibit unstable electric characteristics due to deviations in stoichiometric composition and the presence of hydrogen or moisture, leading to changes in electron donor behavior and oxygen vacancy formation.
Innovation Solution
A method involving the formation of a crystalline oxide semiconductor film with a c-axis perpendicular to the surface, where oxygen is added to amorphize part of the film, followed by heat treatment under an aluminum oxide shield to recrystallize it, resulting in a second crystalline oxide semiconductor film with excess oxygen, which repairs oxygen vacancies and stabilizes electric characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If oxygen is added to the crystalline oxide semiconductor film to repair oxygen vacancies, then electric characteristics stability is improved, but the film may become amorphous and lose its crystalline structure
Solution Approach 1:
The patent applies preliminary action by forming an aluminum oxide film containing excess oxygen before heat treatment. This aluminum oxide film serves as an oxygen source that will supply oxygen to the oxide semiconductor film during subsequent heat treatment, repairing oxygen vacancies while maintaining the crystalline structure through controlled oxygen diffusion.
Solution Approach 2:
The patent utilizes parameter changes by controlling the heat treatment temperature and atmosphere to enable oxygen diffusion from the aluminum oxide film to the oxide semiconductor film. The heat treatment parameters are optimized to repair oxygen vacancies and maintain crystallinity simultaneously, transforming the oxygen deficiency state to a balanced stoichiometric state.
2Stability of the object's composition
If heat treatment is performed to recrystallize the amorphous oxide semiconductor film, then crystalline structure is restored, but oxygen may be released and electric characteristics may deteriorate
Solution Approach 1:
The patent applies beforehand cushioning by providing an aluminum oxide film containing excess oxygen before the heat treatment process. This film acts as a protective cushion that supplies oxygen to the oxide semiconductor film during heat treatment, preventing oxygen release and maintaining electric characteristics stability while enabling crystalline structure restoration.
Solution Approach 2:
The aluminum oxide film serves as an intermediary that mediates the oxygen transfer process. It contains excess oxygen that can be supplied to the oxide semiconductor film during heat treatment, acting as an oxygen reservoir that prevents oxygen loss from the semiconductor film while allowing crystalline structure recovery.
3Stability of the object's composition
If the oxide semiconductor film is kept in contact with aluminum oxide film during heat treatment, then oxygen is supplied to maintain stoichiometry, but the process complexity increases
Solution Approach 1:
The patent applies merging by combining the oxide semiconductor film formation and aluminum oxide film formation into a integrated process sequence. The aluminum oxide film is formed directly over the oxide semiconductor film without additional processing steps, and the subsequent heat treatment simultaneously achieves oxygen supply and crystalline structure restoration, reducing overall process complexity.
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 approach enhances the reliability of semiconductor devices by maintaining stable electric characteristics and reducing variations in threshold voltage, while preventing impurity entry and oxygen release, resulting in high-purity and low-defect crystalline oxide semiconductor films.
Implementation Method 1
oxygen is added to the oxide semiconductor film to amorphize at least part of the oxide semiconductor film
Implementation Method 2
heat treatment is performed thereon to crystallize at least part of the amorphous oxide semiconductor film
Implementation Method 3
an aluminum oxide film is formed over the amorphous oxide semiconductor film, and heat treatment is performed thereon
Data Source
AI summary
A semiconductor device using an oxide semiconductor is provided with stable electric characteristics to improve the reliability. In a manufacturing process of a transistor including an oxide semiconductor film, an oxide semiconductor film containing a crystal having a c-axis which is substantially perpendicular to a top surface thereof (also called a first crystalline oxide semiconductor film) is formed; oxygen is added to the oxide semiconductor film to amorphize at least part of the oxide semiconductor film, so that an amorphous oxide semiconductor film containing an excess of oxygen is formed; an aluminum oxide film is formed over the amorphous oxide semiconductor film; and heat treatment is performed thereon to crystallize at least part of the amorphous oxide semiconductor film, so that an oxide semiconductor film containing a crystal having a c-axis which is substantially perpendicular to a top surface thereof (also called a second crystalline oxide semiconductor film) is formed.