Oxide Semiconductor Transistor with Stacked Crystallinity Layers
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Transistors using oxide semiconductor films face challenges with high field-effect mobility leading to normally-on characteristics and electrical characteristic changes due to oxygen vacancies, which affect reliability and power consumption.
Innovation Solution
A semiconductor device with a stacked structure of oxide semiconductor films, where the middle film has lower crystallinity to act as a diffusion path for excess oxygen, reducing oxygen vacancies and improving reliability, and a composite oxide semiconductor structure with regions of varying indium concentrations to enhance carrier density and mobility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the field-effect mobility is increased to improve transistor performance, then the mobility is improved, but the transistor exhibits normally-on characteristics
Solution Approach 1:
The oxide semiconductor film is divided into multiple layers with different compositions and crystallinities. The first layer has high In content for high mobility, while the second layer has lower In content and lower crystallinity to prevent normally-on characteristics, achieving both high speed and reliability
Solution Approach 2:
Different regions of the oxide semiconductor film have different local compositions and crystallinities. The first layer region has high crystallinity and high In content for mobility, while the second layer region has lower crystallinity and lower In content to suppress normally-on behavior, allowing simultaneous optimization of both parameters
2Reliability
If the amount of oxygen vacancies is reduced to improve reliability, then the reliability is improved, but the field-effect mobility decreases
Solution Approach 1:
The oxide semiconductor film is segmented into two layers where the first layer provides high mobility through high crystallinity and high In content, while the second layer provides reliability through lower oxygen vacancies and lower In content, allowing both requirements to be met simultaneously
Solution Approach 2:
The oxide semiconductor film uses a composite structure of two different oxide semiconductor layers with distinct compositions and properties, combining the advantages of high mobility from one layer and high reliability from the other layer
3Quantity of substance
If hydrogen is trapped in oxygen vacancies to serve as carrier supply source, then the carrier density is increased, but the threshold voltage shifts and electrical characteristics change
Solution Approach 1:
The oxide semiconductor film is divided into layers where the first layer can provide carriers through hydrogen trapping in oxygen vacancies, while the second layer with lower oxygen vacancies prevents excessive threshold voltage shift, balancing carrier density and threshold voltage stability
Solution Approach 2:
Different layers have different local concentrations of oxygen vacancies and hydrogen trapping capabilities. The first layer allows controlled carrier supply while the second layer maintains electrical characteristic stability, achieving both goals through spatial differentiation
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 solution improves field-effect mobility, reduces oxygen vacancies, and enhances the reliability and low power consumption of transistors by effectively managing oxygen diffusion and carrier density within the oxide semiconductor films.
Implementation Method 1
the second oxide semiconductor film includes a region where the crystallinity is lower than the crystallinity of one or both of the first oxide semiconductor film and the third oxide semiconductor film
Data Source
AI summary
To improve field-effect mobility and reliability of a transistor including an oxide semiconductor film. Provided is a semiconductor device including an oxide semiconductor film. The semiconductor device includes a first insulating film, the oxide semiconductor film over the first insulating film, a second insulating film and a third insulating film over the oxide semiconductor film, and a gate electrode over the second insulating film. The oxide semiconductor film includes a first oxide semiconductor film, a second oxide semiconductor film over the first oxide semiconductor film, and a third oxide semiconductor film over the second oxide semiconductor film. The first to third oxide semiconductor films contain the same element. The second oxide semiconductor film includes a region where the crystallinity is lower than the crystallinity of one or both of the first oxide semiconductor film and the third oxide semiconductor film.