Nanowire Transistor Core-Shell Gate Insulation
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Solution Overview
Problem
Conventional nanowire transistors on flexible substrates face challenges with low-temperature gate insulating films, resulting in low breakdown voltages, increased interface levels, and hysteresis due to organic or low-temperature inorganic insulating films, which affect the reliability and performance of the transistors.
Innovation Solution
A nanowire transistor with a core-shell structure, where a semiconductor core is coated with a thick insulating shell, such as silicon dioxide, to serve as a gate insulating film, improving the interface properties and stability of the transistor, and allowing for high-reliability performance on flexible substrates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a low-temperature gate insulating film (organic or low-temperature inorganic insulating film) is used on a flexible substrate, then the transistor can be fabricated at low temperatures suitable for flexible substrates, but the breakdown voltage is low and interface levels are increased, resulting in poor reliability
Solution Approach 1:
The gate insulating film is formed on the nanowire surface before the nanowire is transferred to the flexible substrate. This preliminary formation allows the use of high-quality inorganic insulating films (such as silicon dioxide) that require high-temperature processing, while the actual transistor fabrication on the flexible substrate occurs at low temperatures. The pre-formed gate insulating film is then transferred along with the nanowire to the flexible substrate, resolving the contradiction between low fabrication temperature and high reliability.
2Temperature
If an organic insulating film is used as the gate insulating film, then the transistor can be formed at low temperatures, but hysteresis occurs and the interface properties deteriorate
Solution Approach 1:
The invention uses inorganic insulating films (such as silicon dioxide) that can be thermally processed to form high-quality interfaces without hysteresis, even though these require higher temperatures. The key insight is that the gate insulating film is formed separately on the nanowire before transfer, allowing the use of materials and processes that would be incompatible with direct low-temperature flexible substrate processing. This replaces the problematic organic insulating films with superior inorganic alternatives.
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 core-shell structure enhances the breakdown voltage and reduces interface levels, leading to improved reliability and mobility of the nanowire transistors, with reduced variation in performance and increased stability, even at low temperatures.
Implementation Method 1
the insulating shell portion is made of an insulator including Si and functions as at least a portion of a gate insulating film
Data Source
AI summary
A nanowire transistor according to the present invention includes: at least one nanowire 13 including a core portion 13a that functions as a channel region and an insulating shell portion 13b that covers the surface of the core portion 13a; source and drain electrodes 14 and 15, which are connected to the nanowire 13; and a gate electrode 21 for controlling conductivity in at least a part of the core portion 13a of the nanowire 13. The core portion 13a is made of semiconductor single crystals including Si and has a cross section with a curved profile on a plane that intersects with the longitudinal axis thereof. The insulating shell portion 13b is made of an insulator including Si and functions as at least a portion of a gate insulating film.