GaN HEMT Gate Electrode Grain Boundary Control
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Solution Overview
Problem
The existing GaN-HEMTs suffer from deterioration in gate characteristics and reliability due to the Au electrode material passing through grain boundaries and sidewall interfaces, leading to reaction with the nitride semiconductor surface, especially under high-temperature operation.
Innovation Solution
A manufacturing method for AlGaN/GaN HEMTs that involves forming a gate electrode with a Ni and Au laminated structure, where the edge portion of the through-hole in the passivation film is rounded using wet etching, preventing the Au from reaching the nitride semiconductor surface and inhibiting grain boundary formation at the interface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a Ni and Au laminated structure is used for the gate electrode, then the resistance is reduced and high-frequency characteristics are improved, but Au diffuses through grain boundaries and reacts with the nitride semiconductor surface, deteriorating gate characteristics
Solution Approach 1:
A barrier layer is introduced between the Au electrode material and the nitride semiconductor surface. This intermediate layer prevents Au atoms from diffusing through grain boundaries and reacting with the semiconductor, while maintaining electrical conductivity. The barrier layer acts as a mediator that blocks harmful Au diffusion paths without compromising the low-resistance requirement of the gate electrode.
Solution Approach 2:
The grain boundaries in the Ni layer are oriented parallel to the nitride semiconductor surface before Au deposition. This preliminary structural arrangement creates a geometric barrier that prevents Au atoms from easily penetrating through grain boundaries to reach the semiconductor surface, addressing the diffusion problem before it occurs during device operation.
2Device complexity
If the gate electrode structure is simplified, then manufacturing complexity is reduced, but grain boundaries form at the interface, enabling Au diffusion and reducing reliability
Solution Approach 1:
The Ni layer is formed with predetermined grain boundary orientations (parallel to the semiconductor surface) before Au deposition. This preliminary structural configuration creates an inherent barrier against Au diffusion without requiring complex multi-layer structures, achieving reliability improvement while maintaining manufacturing simplicity.
3Power
If high-temperature operation is enabled to increase power, then device performance is improved, but Au diffusion accelerates and gate characteristics deteriorate
Solution Approach 1:
The barrier layer serves as a thermal and diffusion barrier between the Au electrode and nitride semiconductor. During high-temperature operation, this intermediate layer maintains its structural integrity and continues to block Au diffusion paths, enabling the device to operate at elevated temperatures for increased power output without compromising gate characteristics.
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 enhances the reliability and high-voltage performance of the GaN-HEMTs by limiting gate leak currents and preventing Au diffusion to the Schottky surface, thereby maintaining stable gate characteristics.
Implementation Method 1
the edge portion of the through-hole in the passivation film is rounded using wet etching
Data Source
Figure 1A~1C
Figure 2A~2C
Figure 3A~3C
AI summary
A compound semiconductor device includes a compound semiconductor laminated structure (2), a passivation film (6) formed on the compound semiconductor laminated structure and having a through-hole (6a), and a gate electrode (7) formed on the passivation film so as to plug the through-hole. A grain boundary (101) between different crystalline orientations is formed in the gate electrode, and a starting point of the grain boundary is located apart from the through-hole on a flat surface of the passivation film.