Trapezoidal Metal Gate HEMT for Leakage Reduction
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Solution Overview
Problem
High electron mobility transistors (HEMTs) face limitations due to relatively high leakage current and low gate breakdown voltage, restricting their applications.
Innovation Solution
A HEMT design featuring a trapezoidal metal gate with a semiconductor gate, where the metal gate's edge is inside the semiconductor gate's edge, creating a longer leakage current path and reducing the electrical field, resulting in lower leakage current and higher breakdown voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional HEMT structure is used, then the device achieves high frequency operation capability, but the leakage current is relatively high and gate breakdown voltage is low
Solution Approach 1:
The patent introduces a multi-layer gate structure with vertical stacking of semiconductor gate and metal gate layers, transforming the conventional single-layer planar gate into a three-dimensional composite structure. This dimensional change creates multiple current blocking interfaces and distributes the electric field across different vertical levels, effectively reducing leakage current and increasing breakdown voltage
Solution Approach 2:
The patent employs a composite gate structure combining semiconductor material (e.g., GaN) and metal material (e.g., TiN, Mo, or W) in a stacked configuration. The semiconductor gate provides high electron mobility and control, while the metal gate offers high work function and thermal stability. This composite structure synergistically improves gate breakdown voltage and reduces leakage current compared to conventional single-material gates
2Reliability
If the metal gate edge is positioned inside the semiconductor gate edge, then the leakage current path is lengthened and breakdown voltage increases, but the device complexity increases
Solution Approach 1:
The gate is segmented into distinct semiconductor gate and metal gate layers with different horizontal extents. The metal gate is intentionally designed with a smaller width than the semiconductor gate, creating a stepped configuration. This segmentation allows independent optimization of each layer's function while the overlapping edges create an extended leakage current path that improves breakdown characteristics without requiring complex external structures
Data Source
AI summary
The present disclosure relates to a high electron mobility transistor (HEMT) and a fabrication method thereof. The HEMT may include a substrate; a channel layer disposed on the substrate; a barrier layer disposed on the channel layer; a semiconductor gate disposed on the barrier layer; a metal gate disposed on the semiconductor gate, the metal gate having a trapezoidal cross-sectional shape; and a passivation layer directly contacting the metal gate. A first surface of the metal gate contacts a first surface of the semiconductor gate, and an edge of the first surface of the metal gate is located inside an edge of the first surface of the semiconductor gate.