Oxide Semiconductor Transistor Gate Structure for Oxygen Vacancy Reduction
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Solution Overview
Problem
Oxygen vacancies in oxide semiconductor films and their vicinity can lead to a negative shift in the threshold voltage of transistors, affecting their electric characteristics and reliability.
Innovation Solution
A semiconductor device with an oxide semiconductor film, a gate electrode having a lower oxygen concentration near the interface with the gate insulating film, and a gate insulating film with an oxygen-transmitting property to supply oxygen from the gate electrode to the oxide semiconductor film.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If oxygen vacancies are present in the oxide semiconductor film, then the transistor can be formed with oxide semiconductor material, but the threshold voltage shifts in the negative direction and electric characteristics deteriorate
Solution Approach 1:
Oxygen is supplied to the oxide semiconductor film before transistor operation to prevent oxygen vacancy formation. The gate insulating film with oxygen-transmitting property is prepared in advance, and heat treatment is performed to pre-fill oxygen into the semiconductor film, thereby preventing threshold voltage shifts and maintaining stable electric characteristics throughout device operation.
Solution Approach 2:
A gate insulating film with oxygen-transmitting property is introduced as an intermediary layer between the gate electrode and the oxide semiconductor film. This intermediate layer facilitates oxygen diffusion from the gate electrode region to the semiconductor film, continuously supplying oxygen to prevent vacancy formation and maintain film quality during device operation.
2Reliability
If the gate electrode has high oxygen concentration, then oxygen can be supplied to reduce vacancies, but oxygen may diffuse into the gate electrode causing oxidation and changing gate properties
Solution Approach 1:
The gate insulating film exhibits different functional properties at different locations: it has oxygen-transmitting property in the region contacting the oxide semiconductor film to enable oxygen supply, while maintaining insulation properties in other regions. This spatial variation in material properties allows selective oxygen diffusion without compromising gate electrode integrity or overall device insulation.
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 configuration reduces oxygen vacancies in the oxide semiconductor film, stabilizes the electric characteristics of the transistor, and enhances the reliability of the semiconductor device.
Implementation Method 1
a gate insulating film with an oxygen-transmitting property to supply oxygen from the gate electrode to the oxide semiconductor film
Data Source
AI summary
To reduce oxygen vacancies in an oxide semiconductor film and the vicinity of the oxide semiconductor film and to improve electric characteristics of a transistor including the oxide semiconductor film. A semiconductor device includes a gate electrode whose Gibbs free energy for oxidation is higher than that of a gate insulating film. In a region where the gate electrode is in contact with the gate insulating film, oxygen moves from the gate electrode to the gate insulating film, which is caused because the gate electrode has higher Gibbs free energy for oxidation than the gate insulating film. The oxygen passes through the gate insulating film and is supplied to the oxide semiconductor film in contact with the gate insulating film, whereby oxygen vacancies in the oxide semiconductor film and the vicinity of the oxide semiconductor film can be reduced.