研究目的
To propose and experimentally demonstrate a 1.2 kV rated 4H-SiC OCTFET with an octagonal-cell topology for improved high-frequency figures-of-merit (HF-FOMs) compared to conventional linear-cell MOSFETs.
研究成果
The 4H-SiC OCTFET with octagonal-cell topology was successfully fabricated and demonstrated superior HF-FOMs, with improvements of up to 2.1× for [Ron×Cgd] and 1.4× for [Ron×Qgd] compared to linear-cell MOSFETs. This design offers enhanced high-frequency performance for power switching applications, with optimized JFET width and compact layouts providing significant benefits.
研究不足
The study is limited to 1.2 kV rated devices and specific fabrication processes at X-FAB. The octagonal-cell design may have higher specific on-resistance (Ron,sp) due to lower channel density, and the optimization is focused on HF-FOMs, potentially trading off other performance metrics. The simulations did not fully account for poly-Si bars, which could affect accuracy.
1：Experimental Design and Method Selection:
The study involved optimizing the OCTFET design using TCAD numerical simulations to minimize HF-FOMs, followed by fabrication and experimental validation. The octagonal-cell topology was chosen to reduce reverse transfer capacitance (Cgd) and gate-to-drain charge (Qgd).
2：Sample Selection and Data Sources:
Devices were fabricated on a 6-inch, 4H-SiC Si-face wafer with an n-type epitaxial layer. Linear-cell MOSFETs were fabricated simultaneously for comparison.
3：List of Experimental Equipment and Materials:
A 6-inch foundry (X-FAB) was used for fabrication. Materials included 4H-SiC wafers, poly-Si for gates, and various implants (N and Al). Equipment for TCAD simulations, oxidation, deposition, and electrical characterization was employed.
4：Experimental Procedures and Operational Workflow:
Fabrication steps included implants, activation annealing, gate oxidation, poly-Si deposition and patterning, dielectric deposition, ohmic contact formation, metal deposition, and passivation. Electrical measurements included output characteristics, Cgd, Qgd, and breakdown voltage.
5：Data Analysis Methods:
Data from simulations and measurements were analyzed to calculate Ron,sp, Cgd,sp, Qgd,sp, and HF-FOMs, with comparisons made to linear-cell designs.
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