Oxide Semiconductor Transistor Oxygen Vacancy Reduction
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Solution Overview
Problem
Transistors using oxide semiconductors face issues with oxygen vacancies leading to defects in electric characteristics, reliability concerns, and unstable threshold voltage, often resulting in normally-on devices with high off-state current.
Innovation Solution
The introduction of a method to reduce oxygen vacancies in oxide semiconductor films by adding oxygen to first and second oxide films, which are then transferred to the oxide semiconductor film through heat treatment, using In-Ga-Zn oxide compositions with specific atomic ratios and structures to enhance electric characteristics and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If oxygen is added to oxide films and heat treatment is performed to transfer oxygen to the oxide semiconductor film, then oxygen vacancies are reduced and electric characteristics are improved, but the manufacturing process complexity increases
Solution Approach 1:
Oxygen is added to the first and second oxide films in advance before the oxide semiconductor film is formed. This preliminary oxygen supply ensures that when heat treatment is performed, sufficient oxygen is available to fill vacancies in the semiconductor film, improving reliability without requiring additional oxygen supply steps later in the process
Solution Approach 2:
The first and second oxide films serve as intermediary oxygen reservoirs between the oxygen supply source and the oxide semiconductor film. These intermediary films store oxygen and release it during heat treatment, enabling controlled oxygen transfer to reduce vacancies in the semiconductor film while managing process complexity
2Stability of the object's composition
If oxygen vacancies are reduced through oxygen addition and heat treatment, then threshold voltage stability is improved, but manufacturing time and energy consumption increase
Solution Approach 1:
The formation of the first oxide film, addition of oxygen, formation of the oxide semiconductor film, and subsequent heat treatment for oxygen transfer are integrated into a coordinated sequence. The heat treatment step serves dual purposes: activating the oxygen in the oxide films and facilitating its transfer to the semiconductor film, thereby reducing total process time while achieving threshold voltage stability
Solution Approach 2:
Specific parameters are optimized to balance quality and efficiency: the first oxide film is formed with thickness of 5-50 nm and specific atomic ratios (In:Ga:Zn = 1:1:1 or 1:2:1), oxygen is added to achieve concentration of 1×10^20 to 1×10^22 atoms/cm³, and heat treatment is performed at temperatures of 200-450°C for 1-48 hours. These parameter optimizations ensure effective oxygen transfer and threshold voltage stability while minimizing unnecessary process time and energy consumption
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 improves the electric characteristics and reliability of oxide semiconductor transistors by reducing oxygen vacancies, stabilizing threshold voltage, and minimizing off-state current, resulting in more reliable and efficient semiconductor devices.
Implementation Method 1
the oxygen is diffused to the oxide semiconductor film by heat treatment or the like, so that oxygen vacancies in the oxide semiconductor film are reduced
Implementation Method 2
performing heat treatment so that part of oxygen in the second oxide film is transferred to the oxide semiconductor film
Data Source
AI summary
To improve electric characteristics of a semiconductor device including an oxide semiconductor. Alternatively, to improve reliability of a semiconductor device including an oxide semiconductor. In a transistor including a first oxide film, an oxide semiconductor film, a pair of electrodes in contact with the oxide semiconductor film, and a second oxide film in contact with the oxide semiconductor film and the pair of electrodes, oxygen is added to the first oxide film and the second oxide film in contact with the oxide semiconductor film and the pair of electrodes, so that oxygen vacancies are reduced. The oxygen is diffused to the oxide semiconductor film by heat treatment or the like; thus, oxygen vacancies in the oxide semiconductor film are reduced.