Oxide Semiconductor Film Oxygen Ion Injection Uniformity
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Solution Overview
Problem
In oxide semiconductor transistors, oxygen vacancies lead to shifted threshold voltage and normally-on characteristics, making it challenging to achieve favorable electrical properties due to non-uniform oxygen ion injection, especially at low acceleration voltages which result in insufficient filling of oxygen vacancies.
Innovation Solution
A method involving the formation of a sacrifice film over the oxide semiconductor film to ensure uniform oxygen ion injection by adjusting the acceleration voltage, allowing the local maximum of the concentration distribution to be positioned within the film, thereby improving the uniformity and effectiveness of oxygen ion filling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If oxygen ions are injected at low acceleration voltage, then the injection concentration can be controlled accurately, but the beam current decreases due to space-charge effect and longer time is needed for injection
Solution Approach 1:
The patent applies periodic pulsed ion injection instead of continuous injection. By injecting oxygen ions in periodic pulses, the space charge effect is reduced while maintaining accurate concentration control, thereby decreasing the total injection time and improving productivity without sacrificing precision
2Measurement precision
If oxygen ions are injected at low acceleration voltage, then accurate injection concentration is achieved, but the concentration distribution has a distinct local maximum with larger concentration gradient in depth direction
Solution Approach 1:
Periodic pulsed injection allows oxygen ions to diffuse between pulses, smoothing out the concentration distribution and reducing the distinct local maximum and concentration gradient, thereby improving uniformity while maintaining accurate total concentration control
Solution Approach 2:
The patent changes the injection parameter from continuous low-voltage injection to periodic pulsed injection, modifying the temporal distribution of ion injection to achieve both accurate total concentration and improved depth-wise uniformity
3Measurement precision
If the acceleration voltage is lowered for oxygen ion injection, then accurate injection concentration is achieved, but oxygen vacancies might not be sufficiently filled due to non-uniform concentration
Solution Approach 1:
Periodic pulsed injection with diffusion intervals ensures oxygen ions distribute uniformly throughout the oxide semiconductor film, allowing sufficient filling of oxygen vacancies across the entire film thickness while maintaining accurate total concentration control
Solution Approach 2:
The patent introduces thermal diffusion as an intermediary process between ion injection pulses. This diffusion process acts as a mediator that redistributes the injected oxygen ions uniformly, ensuring complete oxygen vacancy filling while maintaining the benefits of low-voltage accurate injection
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 enables the uniform injection of oxygen ions into the oxide semiconductor film, effectively filling oxygen vacancies and improving the electrical characteristics of the transistor by reducing the concentration gradient and enhancing the uniformity of the ion distribution.
Implementation Method 1
the oxygen vacancies in the oxide semiconductor can be filled by injecting oxygen ions by an ion implantation method or an ion doping method
Data Source
AI summary
An oxide semiconductor film is formed over a substrate. A sacrifice film is formed to such a thickness that the local maximum of the concentration distribution of an injected substance injected into the oxide semiconductor film in the depth direction of the oxide semiconductor film is located in a region from an interface between the substrate and the oxide semiconductor film to a surface of the oxide semiconductor film. Oxygen ions are injected as the injected substance into the oxide semiconductor film through the sacrifice film at such an acceleration voltage that the local maximum of the concentration distribution of the injected substance in the depth direction of the oxide semiconductor film is located in the region, and then the sacrifice film is removed. Further, a semiconductor device is manufactured using the oxide semiconductor film.