Oxide Semiconductor Film Structure for Stable Thin-Film Transistors
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Solution Overview
Problem
The existing techniques for forming oxide semiconductor films in transistors often result in impurities being incorporated into the film, particularly near the surface, which adversely affects the transistor's characteristics and inhibits crystallization, leading to amorphous regions.
Innovation Solution
A semiconductor device is designed with an oxide semiconductor film that includes a first region with a low silicon concentration (≤1.0 at. %) and a crystal portion, formed by sputtering with specific conditions to minimize impurity incorporation and enhance crystallinity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the oxide semiconductor film is made thick to avoid impurity effects, then the impurity concentration in the channel region is reduced, but the parasitic capacitance increases and power consumption increases
Solution Approach 1:
The oxide semiconductor film is divided into two distinct regions: a first region with thickness of 5 nm or less that serves as a buffer layer with higher impurity tolerance, and a second region with lower thickness that forms the active channel. This segmentation allows the channel region to remain thin for low power consumption while the buffer region handles impurity incorporation, resolving the contradiction between avoiding impurities and reducing power consumption.
Solution Approach 2:
The first region acts as an intermediary layer between the gate insulating film and the second region. It absorbs the harmful impurity incorporation effect that would otherwise directly affect the channel region, allowing the use of conventional sputtering methods without compromising channel quality, thus enabling thin film design for low power consumption.
2Productivity
If the oxide semiconductor film is formed by conventional sputtering, then the formation process is simple and productive, but impurity elements are incorporated into the film particularly near the surface
Solution Approach 1:
The film structure is segmented into a first region that intentionally accepts impurities from the sputtering process and a second region that remains relatively pure. This segmentation allows conventional sputtering to be used for high productivity while the buffer region protects the channel region from impurity contamination, maintaining manufacturing precision.
Solution Approach 2:
The impurity incorporation that normally occurs during sputtering is converted from a harmful effect into a beneficial buffer zone. The first region with higher impurity concentration serves as a protective layer, allowing the use of simple and productive sputtering methods while the channel region in the second region maintains the purity needed for precise electrical characteristics.
3Loss of energy
If the oxide semiconductor film is made thin to reduce parasitic capacitance, then power consumption is reduced, but the channel formation region is affected by impurities from the gate insulating film
Solution Approach 1:
The thin oxide semiconductor film is segmented into a first region of 5 nm or less that acts as a protective buffer and a second region that forms the active channel. This segmentation enables the overall film to be thin for low power consumption while the buffer region shields the channel from impurities, maintaining reliability.
Solution Approach 2:
The first region is formed as a preliminary protective layer before the channel-forming second region. This preliminary action of creating a buffer zone prevents impurity incorporation into the channel region, allowing thin film design for low power consumption without compromising transistor characteristics stability.
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 approach effectively reduces impurity concentrations near the surface of the oxide semiconductor film, improves crystallinity, and provides a semiconductor device with stable electric characteristics.
Implementation Method 1
An oxide semiconductor film is formed by a sputtering method
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.