Al₂O₃ Layers Grown by Atomic Layer Deposition as Gate Insulator in 3C-SiC MOS Devices

Area of Science:

• Materials Science
• Semiconductor Physics

Background:

• Metal-oxide-semiconductor (MOS) capacitors are crucial for semiconductor devices.
• Cubic silicon carbide (3C-SiC) is a promising wide-bandgap semiconductor material.
• Optimizing gate insulators is key to improving MOS device performance on 3C-SiC.

Purpose of the Study:

• To investigate the use of Al2O3 as a gate insulator on 3C-SiC.
• To compare thermal and plasma-enhanced Atomic Layer Deposition (ALD) for Al2O3 deposition.
• To analyze the electrical properties and defect characteristics of the Al2O3/SiO2/3C-SiC structures.

Main Methods:

• Fabrication of MOS capacitors using Al2O3 gate insulators on 3C-SiC.
• Deposition of Al2O3 via thermal and plasma-enhanced ALD on a SiO2 interlayer.
• Electrical characterization including flat-band voltage (VFB) shift, leakage current, and breakdown voltage measurements.
• Scanning Capacitance Microscopy (SCM) for analyzing dC/dV distribution.

Main Results:

• Al2O3/SiO2 stacks exhibited significantly lower negative VFB shifts (~ -3 V) compared to SiO2 alone (~ -9 V).
• The reduced VFB shift is attributed to Al2O3's higher permittivity and fewer carbon defects in the thin SiO2 interlayer.
• Plasma-enhanced ALD resulted in Al2O3 layers with better insulating behavior and more uniform leakage current distribution.
• Both thermal and plasma-enhanced ALD achieved a breakdown voltage of 26 V, but thermal ALD showed higher current density above 15 V.

Conclusions:

• Al2O3/SiO2 stacks offer improved performance for MOS capacitors on 3C-SiC due to reduced VFB shifts and better dielectric properties.
• Plasma-enhanced ALD is a preferred method for depositing high-quality Al2O3 gate insulators on 3C-SiC, leading to superior insulating characteristics.
• The study highlights the potential of Al2O3 as an effective gate dielectric for advanced 3C-SiC based electronic devices.