A High-Temperature Stable Ohmic Contact Process on Lightly Doped n-Type 4H-SiC Based on a W/C Multilayer Structure

Area of Science:

• Materials Science
• Semiconductor Device Fabrication
• Nanotechnology

Background:

• Silicon carbide (SiC) is a key material for high-power and high-temperature electronics.
• Developing stable Ohmic contacts is crucial for SiC device performance, especially at elevated temperatures.
• Existing methods often involve complex processes like ion implantation, leading to drawbacks such as lattice damage and higher costs.

Purpose of the Study:

• To propose and demonstrate a novel method for fabricating high-thermal-stability Ohmic contacts on 4H-SiC.
• To investigate the electrical and thermal stability characteristics of the fabricated contacts.
• To offer a cost-effective and reliable alternative to conventional Ohmic contact fabrication techniques for SiC.

Main Methods:

• Utilized a tungsten/carbon (W/C) multi-nanolayer stacked structure.
• Employed a low-doping-concentration (2.5 × 10^15 cm^-3) n-type epitaxial 4H-SiC layer.
• Applied a 1200 °C rapid thermal process (RTP) for annealing.

Main Results:

• Achieved a specific contact resistance (ρc) of 2.53 × 10^-4 Ω·cm² at room temperature.
• Demonstrated a significantly reduced ρc of 1.29 × 10^-5 Ω·cm² at 500 °C.
• Exhibited excellent long-term operational reliability, maintaining stable performance during a 100-hour test at 500 °C in air without degradation.

Conclusions:

• The proposed W/C multi-nanolayer structure combined with RTP provides highly stable Ohmic contacts on low-doped 4H-SiC.
• This fabrication method avoids ion implantation, thus preventing lattice damage and reducing overall manufacturing costs.
• The demonstrated high thermal stability makes this approach ideal for advanced SiC-based devices operating at elevated temperatures.