Comparison of microwave ECR and RF plasmas for dry etching of single crystal 6H-SiC

Electron cyclotron resonance (ECR) plasma etching of single crystal 6H-SiC has been investigated using a CF₄/O₂ gas mixture and compared to conventional reactive ion etching (RIE) in a radio frequency (13.56 MHz) reactor. The use of ECR results in higher etch rates, lower levels of bias and smoother etched surfaces than rf-RIE. ECR etch rates exceeding 100 nm/min have been obtained at a substrate bias of -100 V. Etch rate and surface morphology have been studied as a function of pressure, bias and power. Auger electron spectroscopy shows that ECR etching leaves no residues unlike rf-RIE which leaves residues containing Al, F, O and C. The current-voltage and capacitance-voltage measurements of Schottky diodes show that there is far less damage induced by ECR etching compared to rf-RIE.