Nitride HEMT Gate Dielectric Structure for Parasitic Capacitance Reduction
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Solution Overview
Problem
The frequency characteristics of nitride-based high electron mobility transistors are hindered by parasitic capacitance, particularly between the gate electrode and the semiconductor layer, due to the unstable structure of the T-shaped gate electrode, which limits the ability to enhance frequency performance beyond device scaling.
Innovation Solution
A nitride-based high electron mobility transistor design featuring a dielectric structure around the gate electrode, where the width of the inner sidewall at the bottom end is smaller than at the top end, reducing fringing capacitance and enhancing structural stability, thereby improving frequency characteristics and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the upper portion of the gate electrode is formed to have a large area and spaced apart from the semiconductor layer, then gate resistance is reduced and parasitic capacitance is reduced, but the structure becomes unstable and it is difficult to further widen the gate or increase separation
Solution Approach 1:
A dielectric layer is introduced as an intermediary component between the gate electrode and the semiconductor layer. This dielectric mediator allows the gate electrode to be spaced further from the semiconductor layer, reducing parasitic capacitance and improving frequency characteristics, while the dielectric itself provides structural support to maintain stability. The dielectric acts as a cushioning intermediary that enables greater separation without compromising structural integrity.
2Reliability
If the device is scaled down, then frequency characteristics are improved through device scaling technology, but short channel effect increases and drain current control ability decreases
Solution Approach 1:
The dielectric layer serves as a mediator that reduces the harmful capacitive coupling between the gate electrode and semiconductor layer. By introducing this intermediate layer with appropriate dielectric properties, the parasitic capacitance is reduced, which mitigates the negative effects of short channel phenomenon and improves drain current control ability while maintaining scaled dimensions.
3Area of stationary object
If the gate electrode is closer to the semiconductor layer, then device area is reduced, but parasitic capacitance increases and frequency characteristics deteriorate
Solution Approach 1:
The dielectric layer acts as a space-efficient intermediary that provides electrical isolation between the gate electrode and semiconductor layer. This mediator enables effective parasitic capacitance reduction without requiring excessive vertical spacing, thus maintaining compact device area while improving frequency characteristics through reduced capacitive coupling.
Data Source
AI summary
Provided are a nitride-based high electron mobility transistor having enhanced frequency characteristics and an improved structural stability and manufacturing method thereof. The nitride-based high electron mobility transistor includes a first semiconductor layer and a second semiconductor layer sequentially formed on a substrate, source drain electrodes formed on the second semiconductor layer, a first insulating film formed on the second semiconductor layer and having an opening, a dielectric formed on the first insulating film to surround the opening of the first insulating film, a second insulating film formed on an inner sidewall of the dielectric, and a gate electrode formed on the dielectric to fill the opening of the first insulating film and inside the inner sidewall of the dielectric. A width of the inner sidewall at a bottom end of the dielectric is smaller than a width of the inner sidewall at a top end of the dielectric.