Reactive Plasma Jet High-Rate Etching of SiC

The material removal of SiC utilizing a 2.45 GHz microwave-driven plasma jet source in comparison with a 13.56 MHz RF excited plasma jet source at atmospheric pressure has been investigated. A coaxial nozzle with a central tube for helium, CF4 and O-2 feeding the plasma and the outer ring-shaped nozzle for N-2 to shield the plasma jet from the surrounding air is applied. Additionally an O-2 gas flow is provided and its effect on the etching rate is discussed for varied [CF4]/[O-2] ratios. By optimizing the ratio of CF4 and O-2 gas flow an improvement in etching rates and a change in surface roughness have been found. An increase of the etching rate with a decrease of the CF4 ratio has been detected for both jets. The etching rate of the microwave excited jet has been improved additionally by heating the SiC sample up to 350 degrees C.