IN-SITU STUDY OF PROCESSES TAKING PLACE ON SILICON SURFACE DURING ITSBOMBARDMENT BY CFX AR IONS - ETCHING VERSUS POLYMERIZATION/

The application of a Kaufman ion source in the study of the etching/po lymerization processes taking place at the surface of a silicon substr ate being exposed to ion beams generated from CF4/Ar gas mixtures is r eported. The processes were analyzed by means of in situ mass and ener gy spectroscopy of the secondary ions sputtered from the substrate sur face and the charge-exchange ions, respectively. These analytical meth ods confirmed the growth of the polymer C-F thin films on the silicon surface at higher concentrations of CF4 in the mixture. It was found t hat there existed a primary beam threshold energy above which the poly mer thin film stopped growing and the etch yield of silicon atoms was increased. The simplified activated growth model presented here descri bes this behavior qualitatively as a competition between creative and destructive processes leading to deposition and removal of the thin po lymer film, respectively. (C) 1996 American Vacuum Society.