Comparison of Electron Cyclotron Resonance Dry Etch Chemistries for SiliconCarbide

摘要

Plasma etching using an electron cyclotron resonance (ECR) source has been usedto study dry etching of SiC. Gas chemistries studied include C12/Ar, Cl2/ H2, SF6/Ar, IBr/Ar, and Ar. The variables studied include ECR power (400 to 1000 W), RF power (50 to 350 W), chamber pressure (1.5 to 10 mTorr), and active to total gas flow rate ratios (0 to 1). Etch rates in excess of 2000 A/min. have been achieved with SF6/Ar ECR discharges at low power (400 Watts) and moderate RF power (100-150 Watts). The rates for Cl2/Ar are comparable to SF6/Ar rates with those for Cl2/ H2 being somewhat lower. IBr/Ar is found to be a very poor chemistry for SiC with etch rates reaching only 1000 A/min. Pure Ar sputtering achieved rates of less than 800 A/min. Smooth surfaces (0.6-0.8 nm RMS roughness) have been achieved in all plasma chemistries with no dependence of roughness on plasma conditions. Auger electron analysis confirmed carbon enrichment of the surface in most cases. High RF biases resulted in stoichiometric termination of the SiC surface. Silicon depletion was noted for low RF biases and high chlorine content plasmas. Contamination by F and S was noted in SF6/Ar discharges. All gas chemistries studied favored the chemically dominant side of the theoretical etch rate curve with the exception of pure argon, which favored the sputter dominant side. Chlorine showed the most synergistic effects and covered the largest range of the theoretical etch rate curve for the experimental conditions studied.