Investigation of Interface and Reliability of 3C- and 4H-SiC MOS Structures through Gate Dielectric Stacking and Post-Deposition Annealing

Abstract:

This study investigates the interface and reliability of metal-oxide-semiconductor capacitors (MOSCAPs) based on 3C-SiC and 4H-SiC using atomic layer deposition (ALD) and post-deposition annealing (PDA). SiO₂ and HfO₂/SiO₂ were used as dielectric layers, with systematic PDA treatments conducted at 600°C, 900°C, and 1100°C in N₂ or forming gas (FG, a mixture of H₂ and N₂) environments to evaluate the impact of the PDA conditions on the interface characteristics of SiC MOSCAPs. The flat-band voltage for 3C-SiC MOSCAPs averaged at 0.68 ± 0.05 V for SiO₂/3C-SiC/Si samples and 2.35 ± 0.01 V for HfO₂/SiO₂/3C-SiC samples when MOSCAPs annealed at 1100°C in FG. PDA in forming gas also significantly reduced hysteresis, dropping from 1.75 V to 0.18 V for SiO₂/3C-SiC and from 2.49 V to 0.04 V for HfO₂/SiO₂/3C-SiC samples. For 4H-SiC MOSCAPs, as-deposited devices exhibited high oxide charges and poor interface quality. The average flat-band voltages for SiO₂/4H-SiC were 9.01 ± 0.15 V, while HfO₂/SiO₂ MOSCAPs showed 6.65 ± 0.02 V. After PDA at 1100°C, the flat-band voltage improved to-0.65 ± 0.035 V for SiO₂/4H-SiC and-0.50 ± 0.05 V for HfO₂/SiO₂/4H-SiC. Additionally, hysteresis was reduced from 0.61 V to 0.15 V for SiO₂/4H-SiC and from 0.23 V to 0.05 V for HfO₂/SiO₂/4H-SiC samples. We propose a figure of merit (FOM) which is defined as the ratio of the breakdown field to the product of flatband voltage shift, hysteresis effect, and density of interface states. The results demonstrate that PDA significantly enhances the interface quality and electrical characteristics of the MOS capacitors (MOSCAPs), with nitrogen (N₂) PDA yielding higher FOM for 4H-SiC stacks and forming FG PDA showing superior interfacial quality for 3C-SiC stacks.

• Periodical: Materials Science Forum (Volume 1158)
• Pages: 67-74
• DOI: https://doi.org/10.4028/p-q2IYST
• Online since: September 2025
• Authors: Mustafa Akif Yildirim*, Vishal Ajit Shah, Marina Antoniou, Andrew Newton, Sami Bolat, Gerard Colston, Andrew Graham, Richard Jefferies, James A. Gott, Kushani Perera, Michael J. Powell, Peter Michael Gammon, Philip Andrew Mawby, Robert Gunn, Arne Benjamin Renz
• Keywords: Atomic Layer Deposition, High-κ Dielectrics, Post-Deposition Annealing

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