CARBON REACTIONS IN REACTIVE ION ETCHED SILICON

Reactive ion etching (RIE) of silicon creates interstitial defects in the near surface region which diffuse into the bulk material and are trapped at substitutional carbon sites. Photoluminescence (PL), current-voltage (I-V), and Rutherford backscattering (RBS) measurements show that silicon etched in a CF4 + 8%O2 or SF6 + 8%O2 plasma consists of two distinct regions, a displacement damage region extending 1000 angstrom from the surface and a point defect reaction region which can extend to depths > 1-mu-m. The size of the point defect reaction region is determined by diffusion limited trapping of the interstitial silicon generated during the RIE resulting in the formation of C(i) - O(i) or C(s) - C(i) defect pairs. The long range diffusion rate of the interstitial defects is enhanced by the plasma during the RIE processing, and by a recombination enhanced reaction path.