Comparison of dry etch chemistries for SiC

SiC has generally been plasma etched in polymer-forming chemistries such as CHF3/O-2 or CF4/O-2, often with addition of H-2 to achieve acceptable surface morphologies. We find that under high ion density conditions gases such as SF6, NF3, IBr, and Cl-2 produce smooth surfaces that are free of hydrogen passivation effects. Etch rates in excess of 1500 Angstrom/min are achieved in electron cyclotron resonance (ECR) NF3 or Cl-2/Ar discharges with low additional rf chuck powers (100-150 W); dc bias of -120 to -170 V. The rates are somewhat lower (factors of 2-4) with IBr and SF6 chemistries, Ion-induced damage is evident from Hall measurements for SIC exposed to rf powers >150 W (dc bias >-170 V) under ECR conditions and >250 W (dc bias >-275) under reactive ion etch conditions. Efforts to anneal damage at these higher powers reveals a major annealing stage is evident at similar to 700 degrees C, with an activation energy of similar to 3.4 eV, but there is significant damage remaining even after 1050 degrees C annealing. Hydrogen passivation is a problem only in p-type SiC, and is removed at similar temperatures to ion-induced damage by annealing at similar to 700 degrees C under N-2 ambients. This is strongly correlated with secondary ion mass spectrometry measurements on deuterated samples annealed at different temperatures. (C) 1997 American Vacuum Society.