Oxide Semiconductor Film Structure for Low-Capacitance Crystallization
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Solution Overview
Problem
The existing methods for forming oxide semiconductor films in semiconductor devices often result in high impurity concentrations at the surface, which hinder crystallization and lead to adverse effects on transistor characteristics, such as parasitic capacitance and reduced power operation.
Innovation Solution
A semiconductor device structure is developed with an oxide semiconductor film having a region with a silicon concentration less than or equal to 1.0 at. % near the gate insulating film interface, and a crystal portion is formed in this region to reduce impurity effects, while maintaining a thin film thickness to minimize parasitic capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the oxide semiconductor film is made thick to use a crystal region formed in the surface layer, then crystallinity is improved, but parasitic capacitance increases and power consumption increases
Solution Approach 1:
The invention applies local quality by creating a specific structure where only the surface layer region of the oxide semiconductor film (within 5 nm from the surface) contains a crystal portion, while the bulk remains amorphous. This localized crystallization in the channel formation region provides the necessary crystallinity for stable electrical characteristics without requiring the entire film to be thick and crystalline, thus avoiding increased parasitic capacitance and power consumption associated with thicker films.
2Loss of energy
If the oxide semiconductor film is made thin to reduce parasitic capacitance, then power consumption is reduced, but crystallization is inhibited due to impurity elements at the formed film surface
Solution Approach 1:
The invention applies preliminary action by performing plasma treatment on the gate insulating film surface before forming the oxide semiconductor film. This preliminary plasma treatment removes impurity elements (such as silicon) from the gate insulating film surface, creating a clean interface that does not inhibit crystallization. As a result, the oxide semiconductor film can be made thin to reduce parasitic capacitance while still achieving crystallization in the channel formation region near the gate insulating film interface.
3Productivity
If sputtering method is used to form the oxide semiconductor film, then film formation is efficient, but impurity elements enter the film from the gate insulating film surface
Solution Approach 1:
The invention applies preliminary anti-action by performing plasma treatment on the gate insulating film surface before the sputtering process. This preliminary treatment creates a protective effect by removing impurity elements from the surface, preventing them from entering the oxide semiconductor film during subsequent sputtering. This allows efficient film formation by sputtering to continue while preventing the harmful effect of impurity contamination in the formed film.
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 reduces impurity concentrations and enhances crystallinity, resulting in stable electric characteristics and improved performance of the semiconductor device.
Implementation Method 1
at least the first region includes a crystal portion
Implementation Method 2
An oxide semiconductor film used in a transistor is formed by a sputtering method in many cases
Data Source
AI summary
A semiconductor device includes a gate electrode, a gate insulating film which includes oxidized material containing silicon and covers the gate electrode, an oxide semiconductor film provided to be in contact with the gate insulating film and overlap with at least the gate electrode, and a source electrode and a drain electrode electrically connected to the oxide semiconductor film. In the oxide semiconductor film, a first region which is provided to be in contact with the gate insulating film and have a thickness less than or equal to 5 nm has a silicon concentration lower than or equal to 1.0 at. %, and a region in the oxide semiconductor film other than the first region has lower silicon concentration than the first region. At least the first region includes a crystal portion.