We have conducted characterization of a scanning plasma enhanced chemical vapor deposition (PECVD) system for producing controlled nonuniform deposition or etching profiles. Both self-bias and plasma potential showed that the plasma conditions were disturbed significantly when the source was very close to the chamber wall but electron temperature and ion density were not affected significantly. It was found that a very thin but long tail of parasitic deposition was present over the entire large substrate. To eliminate the parasitic deposition an aperture (plasma guarding house) was constructed and was found to eliminate the parasitic plasma deposition. Deposited silicon nitride and silicon oxide thin films using the plasma guarding house in the scanning PECVD system showed very good optical properties similar to those obtained in conventional deposition methods. No multilayer structure was observed in TEM analysis on these films. (c) 2005 Elsevier B.V. All rights reserved.