SiC Doping Impact during Conducting AFM under Ambient Atmosphere.

Area of Science:

• Materials Science
• Surface Science
• Nanotechnology

Background:

• Electrical atomic force microscopy (AFM) is crucial for nanoscale characterization of silicon carbide (SiC).
• Conductive AFM (C-AFM) can induce unintended surface modification on SiC due to electric fields and water nanomeniscus formation in ambient conditions.

Purpose of the Study:

• To experimentally investigate the effects of anodization during C-AFM measurements on SiC.
• To determine the influence of doping levels on SiC anodization.
• To understand the local oxidation mechanism in SiC-MOSFET structures.

Main Methods:

• Studied nitrogen-doped SiC epitaxial layers with doping from 5 × 10¹⁷ to 10¹⁹ at/cm³.
• Probed water nanomeniscus presence and volume changes using AFM force-distance curves under bias.
• Developed a 2D-axisymmetric finite element model incorporating water nanomeniscus, oxide layer, and doping levels for electrostatic analysis.
• Characterized planar SiC-MOSFETs using C-AFM and confirmed oxide composition with wet chemical etching.

Main Results:

• Water nanomeniscus volume increased threefold under polarization.
• Anodization occurred in a conductive regime strongly dependent on doping, with a threshold of 7 × 10¹⁸ at/cm³.
• C-AFM on SiC-MOSFETs revealed local oxidation on both sides of the MOS channel, corresponding to highly n-type doped zones.
• The induced oxide was identified as a SiOCH layer.

Conclusions:

• The study elucidates the mechanism of local anodic oxidation in SiC during C-AFM, influenced by doping concentration and water nanomeniscus.
• A critical doping level for SiC anodization under C-AFM was identified.
• Understanding this phenomenon is vital for accurate nanoscale characterization and device fabrication of SiC.