Interaction of low-energy ions with silicon surfaces

This work is concerned with obtaining a basic understanding of low-energy (≤ 1.0 keV) ion-semiconductor surface interactions; specifically the work studies the damage and contamination effects in Si, which result from low-energy ion bombardment. It is found in this study that the bombardment by low-energy ions (both inert and reactive) introduces a structurally damaged layer at Si in the near surface region (a few hundred angstroms in thickness). Sample temperatures during the ion exposure are found to influence the crystallinity of this damaged Si layer. Also, the intrinsic damage in this modified Si surface layer manifests itself as donor-like states which pin the Fermi level and also provide positive charge, leading to the metal/silicon barrier height reduction for n-type material and barrier-height enhancement for p-type material. However, for ion-surface chemistries that include residue layer formation, these barrier-height changes caused by ion exposure are in series with the transport impediment presented by the residue layer. The effects of doping of chemically reactive halo-carbon plasma with H on the damage/contamination of Si surface are also studied. It is observed that the addition of H into halo-carbon plasma modifies the structural, electrical, and surface chemical properties of the damaged Si top layer significantly