GaN Semiconductor Flat Band Voltage Stability
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Solution Overview
Problem
High-temperature heat treatment in semiconductor device manufacturing leads to a decrease in flat band voltage and threshold voltage, causing the semiconductor device to become normally-on type, which is undesirable for power circuits, and results in increased interface state density at the semiconductor-insulating film interface.
Innovation Solution
A semiconductor device with a gallium-containing group III-V compound semiconductor layer and a silicon-containing insulating film, where the gallium concentration in the insulating film is controlled to be less than 1.0×10^18 cm^-3 within 30 nm of the interface, and a heat treatment process is performed at a temperature lower than 600°C to suppress voltage decreases and interface state density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high-temperature heat treatment is performed to improve insulating properties and reduce interface state density, then the insulating properties are improved, but flat band voltage and threshold voltage decrease
Solution Approach 1:
The patent changes the temperature parameter of heat treatment from conventional high temperatures (900°C) to a lower temperature range (400-600°C). This parameter change allows the heat treatment to improve insulating properties and reduce interface state density while preventing the decrease in flat band voltage and threshold voltage that occurs at higher temperatures.
2Reliability
If high-temperature heat treatment is performed to reduce interface state density, then interface state density is reduced, but threshold voltage decreases and device becomes normally-on type
Solution Approach 1:
The patent applies parameter changes by reducing the heat treatment temperature to 400-600°C, which achieves reduction in interface state density while maintaining threshold voltage at appropriate levels to ensure normally-off type device operation, preventing the device from becoming normally-on type.
Solution Approach 2:
The patent performs heat treatment at optimized lower temperatures as a preliminary action before final device characterization, allowing interface state density to be reduced while maintaining voltage characteristics. This preliminary optimized treatment prevents the need for higher temperature treatments that would cause voltage degradation.
3Reliability
If conventional heat treatment at 900°C for 20 minutes is performed, then insulating properties are improved, but flat band voltage and threshold voltage decrease significantly
Solution Approach 1:
The patent changes both temperature and time parameters of heat treatment. Instead of 900°C for 20 minutes, the patent uses 400-600°C for appropriately optimized durations. This parameter change achieves the necessary insulating property improvement while maintaining flat band voltage at acceptable levels.
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 effectively reduces the decrease in flat band voltage and threshold voltage, maintaining a normally-off type semiconductor device and minimizing interface state density, thereby enhancing the device's performance and reliability for power circuits.
Implementation Method 1
an average density of gallium in the first insulating film between an interface of the first insulating film and the semiconductor layer and a plane away from the interface by 30 nm is less than 1.0×10^18 cm−3
Implementation Method 2
a heat treatment process is performed at a temperature lower than 600°C to suppress voltage decreases and interface state density
Data Source
AI summary
There is provided a semiconductor device comprising a semiconductor layer that is made of a gallium-containing group III-V compound; and a first insulating film that is in contact with the semiconductor layer and contains silicon. An average density of gallium in the first insulating film between an interface of the first insulating film and the semiconductor layer and a plane away from the interface by 30 nm is less than 1.0×1018 cm−3. This configuration suppresses a decrease in flat band voltage and a decrease in threshold voltage.